<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with Wdesk from Workiva-->
<!--Copyright 2021 Workiva-->
<!--r:11fa41d1-3433-446d-a841-a1f6b381674a,g:69de5f33-6545-4e66-987a-9d22108af5df-->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/Cover" xlink:type="simple" xlink:href="nrg-20201231.xsd#Cover"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/Cover" xlink:type="extended" id="ice87fa95cfed4c9e969a598a77741ad9_Cover"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/CONSOLIDATEDSTATEMENTSOFOPERATIONS" xlink:type="simple" xlink:href="nrg-20201231.xsd#CONSOLIDATEDSTATEMENTSOFOPERATIONS"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/CONSOLIDATEDSTATEMENTSOFOPERATIONS" xlink:type="extended" id="i18e0f76b21934fe3b4d44318922b752d_CONSOLIDATEDSTATEMENTSOFOPERATIONS"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/CONSOLIDATEDSTATEMENTSOFCOMPREHENSIVEINCOME" xlink:type="simple" xlink:href="nrg-20201231.xsd#CONSOLIDATEDSTATEMENTSOFCOMPREHENSIVEINCOME"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/CONSOLIDATEDSTATEMENTSOFCOMPREHENSIVEINCOME" xlink:type="extended" id="i1f8f7e1ea49447318c2be67619fc66e8_CONSOLIDATEDSTATEMENTSOFCOMPREHENSIVEINCOME"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/CONSOLIDATEDSTATEMENTSOFCOMPREHENSIVEINCOMELOSSStatement" xlink:type="simple" xlink:href="nrg-20201231.xsd#CONSOLIDATEDSTATEMENTSOFCOMPREHENSIVEINCOMELOSSStatement"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/CONSOLIDATEDSTATEMENTSOFCOMPREHENSIVEINCOMELOSSStatement" xlink:type="extended" id="i781f310780694bf6830b8577da07fbb1_CONSOLIDATEDSTATEMENTSOFCOMPREHENSIVEINCOMELOSSStatement"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/CONSOLIDATEDSTATEMENTSOFCOMPREHENSIVEINCOMELOSSParentheticals" xlink:type="simple" xlink:href="nrg-20201231.xsd#CONSOLIDATEDSTATEMENTSOFCOMPREHENSIVEINCOMELOSSParentheticals"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/CONSOLIDATEDSTATEMENTSOFCOMPREHENSIVEINCOMELOSSParentheticals" xlink:type="extended" id="icea44617eb314ebbb66601b47bcb8175_CONSOLIDATEDSTATEMENTSOFCOMPREHENSIVEINCOMELOSSParentheticals"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/CONSOLIDATEDBALANCESHEETS" xlink:type="simple" xlink:href="nrg-20201231.xsd#CONSOLIDATEDBALANCESHEETS"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/CONSOLIDATEDBALANCESHEETS" xlink:type="extended" id="i64863d8c79ad4ce28602d5e091005440_CONSOLIDATEDBALANCESHEETS"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/CONSOLIDATEDBALANCESHEETSParenthetical" xlink:type="simple" xlink:href="nrg-20201231.xsd#CONSOLIDATEDBALANCESHEETSParenthetical"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/CONSOLIDATEDBALANCESHEETSParenthetical" xlink:type="extended" id="ie1377aa5693f46179c649bfb615fe52a_CONSOLIDATEDBALANCESHEETSParenthetical"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/CONSOLIDATEDSTATEMENTSOFCASHFLOWS" xlink:type="simple" xlink:href="nrg-20201231.xsd#CONSOLIDATEDSTATEMENTSOFCASHFLOWS"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/CONSOLIDATEDSTATEMENTSOFCASHFLOWS" xlink:type="extended" id="i9c26023432ab43d88c40d6521e6f99b6_CONSOLIDATEDSTATEMENTSOFCASHFLOWS"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/CONSOLIDATEDSTATEMENTSOFSTOCKHOLDERSEQUITY" xlink:type="simple" xlink:href="nrg-20201231.xsd#CONSOLIDATEDSTATEMENTSOFSTOCKHOLDERSEQUITY"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/CONSOLIDATEDSTATEMENTSOFSTOCKHOLDERSEQUITY" xlink:type="extended" id="ifb4d5f23ef154223b0aac0788ce061d5_CONSOLIDATEDSTATEMENTSOFSTOCKHOLDERSEQUITY">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_1ce24b9b-9799-4f08-83b4-04b0ed6551b3" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_2c93320c-764d-4c3a-987d-c052ce20e121" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1ce24b9b-9799-4f08-83b4-04b0ed6551b3" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_2c93320c-764d-4c3a-987d-c052ce20e121" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_f9891acf-6c8b-445a-a980-b0753ff8800e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_2c93320c-764d-4c3a-987d-c052ce20e121" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_f9891acf-6c8b-445a-a980-b0753ff8800e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLossIncludingPortionAttributableToNonredeemableNoncontrollingInterest_682d5be8-416e-4a83-b6dc-4c84482df87e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NetIncomeLossIncludingPortionAttributableToNonredeemableNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_2c93320c-764d-4c3a-987d-c052ce20e121" xlink:to="loc_us-gaap_NetIncomeLossIncludingPortionAttributableToNonredeemableNoncontrollingInterest_682d5be8-416e-4a83-b6dc-4c84482df87e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_c408c649-2b7f-4959-baff-f3a8c32e0a84" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_2c93320c-764d-4c3a-987d-c052ce20e121" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_c408c649-2b7f-4959-baff-f3a8c32e0a84" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_SaleofAssetsUnderCommonControl_0bb3aa90-8b24-48e2-85d6-4a8f11bf7bb8" xlink:href="nrg-20201231.xsd#nrg_SaleofAssetsUnderCommonControl"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_2c93320c-764d-4c3a-987d-c052ce20e121" xlink:to="loc_nrg_SaleofAssetsUnderCommonControl_0bb3aa90-8b24-48e2-85d6-4a8f11bf7bb8" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueEmployeeStockPurchasePlan_8931323d-f62b-424b-b628-f18b280c5f99" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockIssuedDuringPeriodValueEmployeeStockPurchasePlan"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_2c93320c-764d-4c3a-987d-c052ce20e121" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueEmployeeStockPurchasePlan_8931323d-f62b-424b-b628-f18b280c5f99" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockValueAcquiredCostMethod_543368ef-feb6-40fc-87cd-87cd56c4267c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TreasuryStockValueAcquiredCostMethod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_2c93320c-764d-4c3a-987d-c052ce20e121" xlink:to="loc_us-gaap_TreasuryStockValueAcquiredCostMethod_543368ef-feb6-40fc-87cd-87cd56c4267c" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_fdd5b837-f03d-4ba5-acc8-a62927f86079" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_2c93320c-764d-4c3a-987d-c052ce20e121" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_fdd5b837-f03d-4ba5-acc8-a62927f86079" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_686dd828-6260-4e7e-94d0-67c2b6e8b260" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockIssuedDuringPeriodValueNewIssues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_2c93320c-764d-4c3a-987d-c052ce20e121" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_686dd828-6260-4e7e-94d0-67c2b6e8b260" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DividendsCommonStockCash_2b213095-49dd-4d7f-bdb1-21cdcaa400da" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DividendsCommonStockCash"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_2c93320c-764d-4c3a-987d-c052ce20e121" xlink:to="loc_us-gaap_DividendsCommonStockCash_2b213095-49dd-4d7f-bdb1-21cdcaa400da" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders_c1236797-3580-4a95-8ea2-6f32b0e553cb" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_2c93320c-764d-4c3a-987d-c052ce20e121" xlink:to="loc_us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders_c1236797-3580-4a95-8ea2-6f32b0e553cb" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_NoncontrollingInterestContributionsfromNoncontrollingInterestHolders_0693cbcc-0c27-4897-ab5b-c5902e7e712d" xlink:href="nrg-20201231.xsd#nrg_NoncontrollingInterestContributionsfromNoncontrollingInterestHolders"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_2c93320c-764d-4c3a-987d-c052ce20e121" xlink:to="loc_nrg_NoncontrollingInterestContributionsfromNoncontrollingInterestHolders_0693cbcc-0c27-4897-ab5b-c5902e7e712d" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_3515a86f-2239-4384-95d2-e1568b2eacab" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoncontrollingInterestDecreaseFromDeconsolidation_10ebee76-6171-4415-8d87-25f6d5507ab5" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NoncontrollingInterestDecreaseFromDeconsolidation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_2c93320c-764d-4c3a-987d-c052ce20e121" xlink:to="loc_us-gaap_NoncontrollingInterestDecreaseFromDeconsolidation_10ebee76-6171-4415-8d87-25f6d5507ab5" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalEquityComponentOfConvertibleDebt_9ba39365-804e-4e45-9e46-7e165a8402ca" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalEquityComponentOfConvertibleDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_2c93320c-764d-4c3a-987d-c052ce20e121" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalEquityComponentOfConvertibleDebt_9ba39365-804e-4e45-9e46-7e165a8402ca" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalOther_d937090c-48f3-468d-8b97-3adb07826414" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalOther"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_2c93320c-764d-4c3a-987d-c052ce20e121" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalOther_d937090c-48f3-468d-8b97-3adb07826414" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_22834120-de5a-4672-82d1-33b4ef90e6a4" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_f1e76f08-6f9b-42d9-a0c9-ee4a556a4e6f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_1ce24b9b-9799-4f08-83b4-04b0ed6551b3" xlink:to="loc_us-gaap_StatementTable_f1e76f08-6f9b-42d9-a0c9-ee4a556a4e6f" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_5a369728-aa4b-400f-8c17-39b8eee034ba" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_f1e76f08-6f9b-42d9-a0c9-ee4a556a4e6f" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_5a369728-aa4b-400f-8c17-39b8eee034ba" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_5a369728-aa4b-400f-8c17-39b8eee034ba_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_5a369728-aa4b-400f-8c17-39b8eee034ba" xlink:to="loc_us-gaap_EquityComponentDomain_5a369728-aa4b-400f-8c17-39b8eee034ba_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_15b820a4-e9f6-4696-8629-5c190a0a066e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_5a369728-aa4b-400f-8c17-39b8eee034ba" xlink:to="loc_us-gaap_EquityComponentDomain_15b820a4-e9f6-4696-8629-5c190a0a066e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_a417b6d7-214f-4339-bff5-8299dc93fa9a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_15b820a4-e9f6-4696-8629-5c190a0a066e" xlink:to="loc_us-gaap_CommonStockMember_a417b6d7-214f-4339-bff5-8299dc93fa9a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_81e1b68a-3397-4bc9-a0c3-739a3c70f812" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AdditionalPaidInCapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_15b820a4-e9f6-4696-8629-5c190a0a066e" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_81e1b68a-3397-4bc9-a0c3-739a3c70f812" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_beb9e040-ac3d-4f5f-b98d-15d7360af468" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RetainedEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_15b820a4-e9f6-4696-8629-5c190a0a066e" xlink:to="loc_us-gaap_RetainedEarningsMember_beb9e040-ac3d-4f5f-b98d-15d7360af468" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockMember_7b3029dd-bc93-4ccf-9cd2-006f39a0673d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TreasuryStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_15b820a4-e9f6-4696-8629-5c190a0a066e" xlink:to="loc_us-gaap_TreasuryStockMember_7b3029dd-bc93-4ccf-9cd2-006f39a0673d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_929785f4-83df-49e2-9b76-999528208e8e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_15b820a4-e9f6-4696-8629-5c190a0a066e" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_929785f4-83df-49e2-9b76-999528208e8e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoncontrollingInterestMember_974c94eb-8eab-4931-9dd3-a11fe26e02d3" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NoncontrollingInterestMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_15b820a4-e9f6-4696-8629-5c190a0a066e" xlink:to="loc_us-gaap_NoncontrollingInterestMember_974c94eb-8eab-4931-9dd3-a11fe26e02d3" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_0a856b13-cdc3-4594-907d-09fc37c13f89" xlink:href="https://xbrl.sec.gov/dei/2020/dei-2020-01-31.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_f1e76f08-6f9b-42d9-a0c9-ee4a556a4e6f" xlink:to="loc_dei_LegalEntityAxis_0a856b13-cdc3-4594-907d-09fc37c13f89" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_0a856b13-cdc3-4594-907d-09fc37c13f89_default" xlink:href="https://xbrl.sec.gov/dei/2020/dei-2020-01-31.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_0a856b13-cdc3-4594-907d-09fc37c13f89" xlink:to="loc_dei_EntityDomain_0a856b13-cdc3-4594-907d-09fc37c13f89_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_c4792436-6111-42eb-9e3c-a1e980db02e9" xlink:href="https://xbrl.sec.gov/dei/2020/dei-2020-01-31.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_0a856b13-cdc3-4594-907d-09fc37c13f89" xlink:to="loc_dei_EntityDomain_c4792436-6111-42eb-9e3c-a1e980db02e9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_NrgYieldIncMember_a4b4d5ea-0099-423a-bc0d-c8b19cfe8698" xlink:href="nrg-20201231.xsd#nrg_NrgYieldIncMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_c4792436-6111-42eb-9e3c-a1e980db02e9" xlink:to="loc_nrg_NrgYieldIncMember_a4b4d5ea-0099-423a-bc0d-c8b19cfe8698" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CumulativeEffectPeriodOfAdoptionAxis_101746ee-f90b-4f54-875d-8213520f09d0" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_CumulativeEffectPeriodOfAdoptionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_f1e76f08-6f9b-42d9-a0c9-ee4a556a4e6f" xlink:to="loc_srt_CumulativeEffectPeriodOfAdoptionAxis_101746ee-f90b-4f54-875d-8213520f09d0" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CumulativeEffectPeriodOfAdoptionDomain_101746ee-f90b-4f54-875d-8213520f09d0_default" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_CumulativeEffectPeriodOfAdoptionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CumulativeEffectPeriodOfAdoptionAxis_101746ee-f90b-4f54-875d-8213520f09d0" xlink:to="loc_srt_CumulativeEffectPeriodOfAdoptionDomain_101746ee-f90b-4f54-875d-8213520f09d0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CumulativeEffectPeriodOfAdoptionDomain_e964285e-dc79-47c7-a2d3-d04744311dd6" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_CumulativeEffectPeriodOfAdoptionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CumulativeEffectPeriodOfAdoptionAxis_101746ee-f90b-4f54-875d-8213520f09d0" xlink:to="loc_srt_CumulativeEffectPeriodOfAdoptionDomain_e964285e-dc79-47c7-a2d3-d04744311dd6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CumulativeEffectPeriodOfAdoptionAdjustmentMember_a8f2ee20-0361-4bef-976c-aaa028e1db3d" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_CumulativeEffectPeriodOfAdoptionAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_CumulativeEffectPeriodOfAdoptionDomain_e964285e-dc79-47c7-a2d3-d04744311dd6" xlink:to="loc_srt_CumulativeEffectPeriodOfAdoptionAdjustmentMember_a8f2ee20-0361-4bef-976c-aaa028e1db3d" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/CONSOLIDATEDSTATEMENTSOFSTOCKHOLDERSEQUITYParenthetical" xlink:type="simple" xlink:href="nrg-20201231.xsd#CONSOLIDATEDSTATEMENTSOFSTOCKHOLDERSEQUITYParenthetical"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/CONSOLIDATEDSTATEMENTSOFSTOCKHOLDERSEQUITYParenthetical" xlink:type="extended" id="i71aa226cfddd439aad0f7160e83f0b62_CONSOLIDATEDSTATEMENTSOFSTOCKHOLDERSEQUITYParenthetical"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/NatureofBusiness" xlink:type="simple" xlink:href="nrg-20201231.xsd#NatureofBusiness"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/NatureofBusiness" xlink:type="extended" id="iec31aa6661214f7495d7194f10e4f652_NatureofBusiness"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/NatureofBusinessDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#NatureofBusinessDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/NatureofBusinessDetails" xlink:type="extended" id="iba57ab18c8a2439aa1f0e854e55d79f3_NatureofBusinessDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_0c00a71d-feea-4cbe-b3e0-1183c521b8a3" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_NumberOfCustomers_da0345fa-d678-4205-890c-5a90e1ab35b8" xlink:href="nrg-20201231.xsd#nrg_NumberOfCustomers"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_0c00a71d-feea-4cbe-b3e0-1183c521b8a3" xlink:to="loc_nrg_NumberOfCustomers_da0345fa-d678-4205-890c-5a90e1ab35b8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_NumberOfCustomers_6ef2b88f-dc27-42d6-8ffd-4daff7f938b8" xlink:href="nrg-20201231.xsd#nrg_NumberOfCustomers"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NumberOfStatesInWhichEntityOperates_f394fcc3-1622-4502-bd86-8859c3141f2f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NumberOfStatesInWhichEntityOperates"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_0c00a71d-feea-4cbe-b3e0-1183c521b8a3" xlink:to="loc_us-gaap_NumberOfStatesInWhichEntityOperates_f394fcc3-1622-4502-bd86-8859c3141f2f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_NumberOfProvincesInWhichEntityOperates_ba9494d9-4e11-4214-b440-60672fbcd4df" xlink:href="nrg-20201231.xsd#nrg_NumberOfProvincesInWhichEntityOperates"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_0c00a71d-feea-4cbe-b3e0-1183c521b8a3" xlink:to="loc_nrg_NumberOfProvincesInWhichEntityOperates_ba9494d9-4e11-4214-b440-60672fbcd4df" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_bdbb301f-8a6c-49a7-9ec3-549915f485c7" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_0c00a71d-feea-4cbe-b3e0-1183c521b8a3" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_bdbb301f-8a6c-49a7-9ec3-549915f485c7" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_984c3a95-7ff1-4dcd-b795-99ca5eefa4b1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_bdbb301f-8a6c-49a7-9ec3-549915f485c7" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_984c3a95-7ff1-4dcd-b795-99ca5eefa4b1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_984c3a95-7ff1-4dcd-b795-99ca5eefa4b1_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_984c3a95-7ff1-4dcd-b795-99ca5eefa4b1" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_984c3a95-7ff1-4dcd-b795-99ca5eefa4b1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_de113234-a1c7-4e66-83fd-ffe8672d9511" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_984c3a95-7ff1-4dcd-b795-99ca5eefa4b1" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_de113234-a1c7-4e66-83fd-ffe8672d9511" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_DirectEnergyMember_7d41c4e3-a3b7-47d9-95e0-4e9285982386" xlink:href="nrg-20201231.xsd#nrg_DirectEnergyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_de113234-a1c7-4e66-83fd-ffe8672d9511" xlink:to="loc_nrg_DirectEnergyMember_7d41c4e3-a3b7-47d9-95e0-4e9285982386" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_51ed1583-490e-4075-ae79-29926b69cbc0" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_bdbb301f-8a6c-49a7-9ec3-549915f485c7" xlink:to="loc_srt_StatementGeographicalAxis_51ed1583-490e-4075-ae79-29926b69cbc0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_51ed1583-490e-4075-ae79-29926b69cbc0_default" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_51ed1583-490e-4075-ae79-29926b69cbc0" xlink:to="loc_srt_SegmentGeographicalDomain_51ed1583-490e-4075-ae79-29926b69cbc0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_3d0e7abf-9afc-4580-a7b1-84ce51884fd4" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_51ed1583-490e-4075-ae79-29926b69cbc0" xlink:to="loc_srt_SegmentGeographicalDomain_3d0e7abf-9afc-4580-a7b1-84ce51884fd4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_US_f53b7d0b-ffbd-4b15-be24-60547a2f219b" xlink:href="https://xbrl.sec.gov/country/2020/country-2020-01-31.xsd#country_US"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_3d0e7abf-9afc-4580-a7b1-84ce51884fd4" xlink:to="loc_country_US_f53b7d0b-ffbd-4b15-be24-60547a2f219b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_CA_d22ac66c-b569-4fba-8ff8-2396a47b69e8" xlink:href="https://xbrl.sec.gov/country/2020/country-2020-01-31.xsd#country_CA"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_3d0e7abf-9afc-4580-a7b1-84ce51884fd4" xlink:to="loc_country_CA_d22ac66c-b569-4fba-8ff8-2396a47b69e8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_09fd3d1e-db56-47fd-93fc-3da01b5d87aa" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_bdbb301f-8a6c-49a7-9ec3-549915f485c7" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_09fd3d1e-db56-47fd-93fc-3da01b5d87aa" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_09fd3d1e-db56-47fd-93fc-3da01b5d87aa_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_09fd3d1e-db56-47fd-93fc-3da01b5d87aa" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_09fd3d1e-db56-47fd-93fc-3da01b5d87aa_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_6ba9c943-0d09-431e-97e3-baf0cbb1fb43" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_09fd3d1e-db56-47fd-93fc-3da01b5d87aa" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_6ba9c943-0d09-431e-97e3-baf0cbb1fb43" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_4022d858-d268-40d4-a270-fcd2f55c2b7d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_6ba9c943-0d09-431e-97e3-baf0cbb1fb43" xlink:to="loc_us-gaap_SubsequentEventMember_4022d858-d268-40d4-a270-fcd2f55c2b7d" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/SummaryofSignificantAccountingPolicies" xlink:type="simple" xlink:href="nrg-20201231.xsd#SummaryofSignificantAccountingPolicies"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/SummaryofSignificantAccountingPolicies" xlink:type="extended" id="ib2aa621d35e34946bc67656c5b89eb38_SummaryofSignificantAccountingPolicies"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/SummaryofSignificantAccountingPoliciesPolicies" xlink:type="simple" xlink:href="nrg-20201231.xsd#SummaryofSignificantAccountingPoliciesPolicies"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/SummaryofSignificantAccountingPoliciesPolicies" xlink:type="extended" id="i14c581443ecf4f8d98f200356ee64f55_SummaryofSignificantAccountingPoliciesPolicies"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/SummaryofSignificantAccountingPoliciesTables" xlink:type="simple" xlink:href="nrg-20201231.xsd#SummaryofSignificantAccountingPoliciesTables"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/SummaryofSignificantAccountingPoliciesTables" xlink:type="extended" id="id649e5258a1e44c397eb723467ea4d3f_SummaryofSignificantAccountingPoliciesTables"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/SummaryofSignificantAccountingPoliciesNetIncomeLossAttributabletoContinuingandDiscontinuedOperationsDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#SummaryofSignificantAccountingPoliciesNetIncomeLossAttributabletoContinuingandDiscontinuedOperationsDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/SummaryofSignificantAccountingPoliciesNetIncomeLossAttributabletoContinuingandDiscontinuedOperationsDetails" xlink:type="extended" id="i3438f4e4cbc746a1a25569774165fc84_SummaryofSignificantAccountingPoliciesNetIncomeLossAttributabletoContinuingandDiscontinuedOperationsDetails"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/SummaryofSignificantAccountingPoliciesAdditionalDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#SummaryofSignificantAccountingPoliciesAdditionalDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/SummaryofSignificantAccountingPoliciesAdditionalDetails" xlink:type="extended" id="i340858f2fee647c8a6ab414e16254a6c_SummaryofSignificantAccountingPoliciesAdditionalDetails">
    <link:loc xlink:type="locator" xlink:label="loc_nrg_SummaryOfSignificantAccountingPoliciesDisclosureLineItems_f0fae68c-7b2c-4f10-a275-966f9f499898" xlink:href="nrg-20201231.xsd#nrg_SummaryOfSignificantAccountingPoliciesDisclosureLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_FundsDepositedByCounterpartiesAbstract_b57a0e3d-aee3-4802-923b-55c02d9e86e2" xlink:href="nrg-20201231.xsd#nrg_FundsDepositedByCounterpartiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_SummaryOfSignificantAccountingPoliciesDisclosureLineItems_f0fae68c-7b2c-4f10-a275-966f9f499898" xlink:to="loc_nrg_FundsDepositedByCounterpartiesAbstract_b57a0e3d-aee3-4802-923b-55c02d9e86e2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_PeriodBeyondwhichComapnyCanNotPredictHoldingofCollateral_0b05f26d-9e21-41c9-8e21-bf00d91851ad" xlink:href="nrg-20201231.xsd#nrg_PeriodBeyondwhichComapnyCanNotPredictHoldingofCollateral"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_FundsDepositedByCounterpartiesAbstract_b57a0e3d-aee3-4802-923b-55c02d9e86e2" xlink:to="loc_nrg_PeriodBeyondwhichComapnyCanNotPredictHoldingofCollateral_0b05f26d-9e21-41c9-8e21-bf00d91851ad" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentAbstract_68a64df9-bfc4-44ae-af58-deb24fe6f8eb" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PropertyPlantAndEquipmentAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_SummaryOfSignificantAccountingPoliciesDisclosureLineItems_f0fae68c-7b2c-4f10-a275-966f9f499898" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentAbstract_68a64df9-bfc4-44ae-af58-deb24fe6f8eb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_JointlyOwnedUtilityPlantProportionateOwnershipShare_bf0896e2-054b-47c3-9075-565bb81c0bc9" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_JointlyOwnedUtilityPlantProportionateOwnershipShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentAbstract_68a64df9-bfc4-44ae-af58-deb24fe6f8eb" xlink:to="loc_us-gaap_JointlyOwnedUtilityPlantProportionateOwnershipShare_bf0896e2-054b-47c3-9075-565bb81c0bc9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_ProjectDevelopmentCostsAndCapitalizedInterestAbstract_e8215b24-e9f4-4892-b6d0-8d16fbe4317b" xlink:href="nrg-20201231.xsd#nrg_ProjectDevelopmentCostsAndCapitalizedInterestAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_SummaryOfSignificantAccountingPoliciesDisclosureLineItems_f0fae68c-7b2c-4f10-a275-966f9f499898" xlink:to="loc_nrg_ProjectDevelopmentCostsAndCapitalizedInterestAbstract_e8215b24-e9f4-4892-b6d0-8d16fbe4317b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestCostsCapitalized_b16bbf4f-e8ae-420b-b958-726186e8ddef" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InterestCostsCapitalized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_ProjectDevelopmentCostsAndCapitalizedInterestAbstract_e8215b24-e9f4-4892-b6d0-8d16fbe4317b" xlink:to="loc_us-gaap_InterestCostsCapitalized_b16bbf4f-e8ae-420b-b958-726186e8ddef" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNetAbstract_c1e0093e-022c-4033-97fe-b89ddacf1f6f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsNetAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_SummaryOfSignificantAccountingPoliciesDisclosureLineItems_f0fae68c-7b2c-4f10-a275-966f9f499898" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsNetAbstract_c1e0093e-022c-4033-97fe-b89ddacf1f6f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_417d31fd-e51d-4a32-b9c6-fc63b4caf73d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsNetAbstract_c1e0093e-022c-4033-97fe-b89ddacf1f6f" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_417d31fd-e51d-4a32-b9c6-fc63b4caf73d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRecognitionAbstract_d5df9a81-f57d-4e72-bdc0-93cffac911bb" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RevenueRecognitionAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_SummaryOfSignificantAccountingPoliciesDisclosureLineItems_f0fae68c-7b2c-4f10-a275-966f9f499898" xlink:to="loc_us-gaap_RevenueRecognitionAbstract_d5df9a81-f57d-4e72-bdc0-93cffac911bb" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LessorOperatingLeaseTermOfContract_6b334918-cf12-47e4-84bd-8a6ff69fbc14" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LessorOperatingLeaseTermOfContract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRecognitionAbstract_d5df9a81-f57d-4e72-bdc0-93cffac911bb" xlink:to="loc_us-gaap_LessorOperatingLeaseTermOfContract_6b334918-cf12-47e4-84bd-8a6ff69fbc14" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LeasesAbstract_74b66175-364d-453a-b8b5-67784c773e10" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LeasesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_SummaryOfSignificantAccountingPoliciesDisclosureLineItems_f0fae68c-7b2c-4f10-a275-966f9f499898" xlink:to="loc_us-gaap_LeasesAbstract_74b66175-364d-453a-b8b5-67784c773e10" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLeaseIncome_198df1e1-eb1f-404c-b961-33871f3c841a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeaseLeaseIncome"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LeasesAbstract_74b66175-364d-453a-b8b5-67784c773e10" xlink:to="loc_us-gaap_OperatingLeaseLeaseIncome_198df1e1-eb1f-404c-b961-33871f3c841a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeasesIncomeStatementContingentRevenue_267e9b9f-3319-4f35-a85c-deff7ada599d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeasesIncomeStatementContingentRevenue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LeasesAbstract_74b66175-364d-453a-b8b5-67784c773e10" xlink:to="loc_us-gaap_OperatingLeasesIncomeStatementContingentRevenue_267e9b9f-3319-4f35-a85c-deff7ada599d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_GrossReceiptsAndSalesTaxesAbstract_49c6588c-207f-4d9d-bcc5-74e42c774ed1" xlink:href="nrg-20201231.xsd#nrg_GrossReceiptsAndSalesTaxesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_SummaryOfSignificantAccountingPoliciesDisclosureLineItems_f0fae68c-7b2c-4f10-a275-966f9f499898" xlink:to="loc_nrg_GrossReceiptsAndSalesTaxesAbstract_49c6588c-207f-4d9d-bcc5-74e42c774ed1" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_GrossReceiptsTax_7a845922-a1a8-4fb5-bf10-5e03716e4bdc" xlink:href="nrg-20201231.xsd#nrg_GrossReceiptsTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_GrossReceiptsAndSalesTaxesAbstract_49c6588c-207f-4d9d-bcc5-74e42c774ed1" xlink:to="loc_nrg_GrossReceiptsTax_7a845922-a1a8-4fb5-bf10-5e03716e4bdc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_CostOfEnergyForRetailOperationsAbstract_bd77e7ef-7a1a-4df4-898a-1c787471eadc" xlink:href="nrg-20201231.xsd#nrg_CostOfEnergyForRetailOperationsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_SummaryOfSignificantAccountingPoliciesDisclosureLineItems_f0fae68c-7b2c-4f10-a275-966f9f499898" xlink:to="loc_nrg_CostOfEnergyForRetailOperationsAbstract_bd77e7ef-7a1a-4df4-898a-1c787471eadc" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_CostOfServicesEnergyServicesUnbilled_648f7c24-c19d-4288-97fa-24e84a649063" xlink:href="nrg-20201231.xsd#nrg_CostOfServicesEnergyServicesUnbilled"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_CostOfEnergyForRetailOperationsAbstract_bd77e7ef-7a1a-4df4-898a-1c787471eadc" xlink:to="loc_nrg_CostOfServicesEnergyServicesUnbilled_648f7c24-c19d-4288-97fa-24e84a649063" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_ForeignCurrencyTranslationAndTransactionAbstract_766ec8d9-f432-42eb-ac6a-e50616fba48c" xlink:href="nrg-20201231.xsd#nrg_ForeignCurrencyTranslationAndTransactionAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_SummaryOfSignificantAccountingPoliciesDisclosureLineItems_f0fae68c-7b2c-4f10-a275-966f9f499898" xlink:to="loc_nrg_ForeignCurrencyTranslationAndTransactionAbstract_766ec8d9-f432-42eb-ac6a-e50616fba48c" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentNetOfTax_2d194a2d-54a4-431d-91a0-5384504dba3b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_ForeignCurrencyTranslationAndTransactionAbstract_766ec8d9-f432-42eb-ac6a-e50616fba48c" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentNetOfTax_2d194a2d-54a4-431d-91a0-5384504dba3b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MarketingAndAdvertisingExpenseAbstract_642570ac-176a-48d5-835d-7c24ea4d8111" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_MarketingAndAdvertisingExpenseAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_SummaryOfSignificantAccountingPoliciesDisclosureLineItems_f0fae68c-7b2c-4f10-a275-966f9f499898" xlink:to="loc_us-gaap_MarketingAndAdvertisingExpenseAbstract_642570ac-176a-48d5-835d-7c24ea4d8111" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdvertisingExpense_ceefef1d-ec55-4541-be4a-d96569bde881" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AdvertisingExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MarketingAndAdvertisingExpenseAbstract_642570ac-176a-48d5-835d-7c24ea4d8111" xlink:to="loc_us-gaap_AdvertisingExpense_ceefef1d-ec55-4541-be4a-d96569bde881" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringAndRelatedActivitiesAbstract_7f701791-3427-4c39-aa72-9f1765663d7f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RestructuringAndRelatedActivitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_SummaryOfSignificantAccountingPoliciesDisclosureLineItems_f0fae68c-7b2c-4f10-a275-966f9f499898" xlink:to="loc_us-gaap_RestructuringAndRelatedActivitiesAbstract_7f701791-3427-4c39-aa72-9f1765663d7f" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringCosts_d6fc3bf7-896e-4e46-adca-f468d3bca74f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RestructuringCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringAndRelatedActivitiesAbstract_7f701791-3427-4c39-aa72-9f1765663d7f" xlink:to="loc_us-gaap_RestructuringCosts_d6fc3bf7-896e-4e46-adca-f468d3bca74f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_SummaryofSignificantAccountingPoliciesTable_877c27c2-2641-4cf5-b782-1a29ff5d41ad" xlink:href="nrg-20201231.xsd#nrg_SummaryofSignificantAccountingPoliciesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_nrg_SummaryOfSignificantAccountingPoliciesDisclosureLineItems_f0fae68c-7b2c-4f10-a275-966f9f499898" xlink:to="loc_nrg_SummaryofSignificantAccountingPoliciesTable_877c27c2-2641-4cf5-b782-1a29ff5d41ad" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_JointlyOwnedUtilityPlantAxis_016cd0f3-78dc-41ea-b344-5ede9298c59a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_JointlyOwnedUtilityPlantAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_nrg_SummaryofSignificantAccountingPoliciesTable_877c27c2-2641-4cf5-b782-1a29ff5d41ad" xlink:to="loc_us-gaap_JointlyOwnedUtilityPlantAxis_016cd0f3-78dc-41ea-b344-5ede9298c59a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_JointlyOwnedUtilityPlantDomain_016cd0f3-78dc-41ea-b344-5ede9298c59a_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_JointlyOwnedUtilityPlantDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_JointlyOwnedUtilityPlantAxis_016cd0f3-78dc-41ea-b344-5ede9298c59a" xlink:to="loc_us-gaap_JointlyOwnedUtilityPlantDomain_016cd0f3-78dc-41ea-b344-5ede9298c59a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_JointlyOwnedUtilityPlantDomain_a3c0e9fc-9703-4941-9fca-3dca54a707b1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_JointlyOwnedUtilityPlantDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_JointlyOwnedUtilityPlantAxis_016cd0f3-78dc-41ea-b344-5ede9298c59a" xlink:to="loc_us-gaap_JointlyOwnedUtilityPlantDomain_a3c0e9fc-9703-4941-9fca-3dca54a707b1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_SouthTexasProjectUnits1And2Member_b67f0514-33c6-4d6f-a752-ec07256faa1a" xlink:href="nrg-20201231.xsd#nrg_SouthTexasProjectUnits1And2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_JointlyOwnedUtilityPlantDomain_a3c0e9fc-9703-4941-9fca-3dca54a707b1" xlink:to="loc_nrg_SouthTexasProjectUnits1And2Member_b67f0514-33c6-4d6f-a752-ec07256faa1a" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/SummaryofSignificantAccountingPoliciesActivityintheAllowanceforCreditLossesDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#SummaryofSignificantAccountingPoliciesActivityintheAllowanceforCreditLossesDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/SummaryofSignificantAccountingPoliciesActivityintheAllowanceforCreditLossesDetails" xlink:type="extended" id="i8af2e6ed566242f3a3cc4125176e6026_SummaryofSignificantAccountingPoliciesActivityintheAllowanceforCreditLossesDetails"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/SummaryofSignificantAccountingPoliciesRestrictedCashDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#SummaryofSignificantAccountingPoliciesRestrictedCashDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/SummaryofSignificantAccountingPoliciesRestrictedCashDetails" xlink:type="extended" id="i38fd12b9c1a34a918c4985eae4ddc3ed_SummaryofSignificantAccountingPoliciesRestrictedCashDetails"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/SummaryofSignificantAccountingPoliciesRedeemableNonControllingInterestDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#SummaryofSignificantAccountingPoliciesRedeemableNonControllingInterestDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/SummaryofSignificantAccountingPoliciesRedeemableNonControllingInterestDetails" xlink:type="extended" id="i6ba2d86b7cc3453dbc728d38ea046871_SummaryofSignificantAccountingPoliciesRedeemableNonControllingInterestDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestLineItems_99016c71-e0c8-481e-909f-4d34e7fd00f0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_MinorityInterestLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_NoncontrollingInterestRollForward_3201d144-b943-4f1a-aad3-c9398e437486" xlink:href="nrg-20201231.xsd#nrg_NoncontrollingInterestRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MinorityInterestLineItems_99016c71-e0c8-481e-909f-4d34e7fd00f0" xlink:to="loc_nrg_NoncontrollingInterestRollForward_3201d144-b943-4f1a-aad3-c9398e437486" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RedeemableNoncontrollingInterestEquityOtherCarryingAmount_1addde7c-f22e-40fe-ac2a-51a406f31181" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RedeemableNoncontrollingInterestEquityOtherCarryingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_NoncontrollingInterestRollForward_3201d144-b943-4f1a-aad3-c9398e437486" xlink:to="loc_us-gaap_RedeemableNoncontrollingInterestEquityOtherCarryingAmount_1addde7c-f22e-40fe-ac2a-51a406f31181" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders_50bedea5-9e5d-43dd-b28c-542799d960fb" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_NoncontrollingInterestRollForward_3201d144-b943-4f1a-aad3-c9398e437486" xlink:to="loc_us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders_50bedea5-9e5d-43dd-b28c-542799d960fb" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_RedeemableNoncontrollingInterestCashContributionsfromNoncontrollingInterestHolders_10ec878d-ea68-45fd-beef-b0e410c00a47" xlink:href="nrg-20201231.xsd#nrg_RedeemableNoncontrollingInterestCashContributionsfromNoncontrollingInterestHolders"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_NoncontrollingInterestRollForward_3201d144-b943-4f1a-aad3-c9398e437486" xlink:to="loc_nrg_RedeemableNoncontrollingInterestCashContributionsfromNoncontrollingInterestHolders_10ec878d-ea68-45fd-beef-b0e410c00a47" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_NoncontrollingInterestNoncashAdjustments_ff6bdce8-6c8d-4113-9b4f-ad04324f8ce5" xlink:href="nrg-20201231.xsd#nrg_NoncontrollingInterestNoncashAdjustments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_NoncontrollingInterestRollForward_3201d144-b943-4f1a-aad3-c9398e437486" xlink:to="loc_nrg_NoncontrollingInterestNoncashAdjustments_ff6bdce8-6c8d-4113-9b4f-ad04324f8ce5" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLossAttributableToRedeemableNoncontrollingInterest_07e65b2c-3f8e-4531-ae3d-f43189ba4681" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NetIncomeLossAttributableToRedeemableNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_NoncontrollingInterestRollForward_3201d144-b943-4f1a-aad3-c9398e437486" xlink:to="loc_us-gaap_NetIncomeLossAttributableToRedeemableNoncontrollingInterest_07e65b2c-3f8e-4531-ae3d-f43189ba4681" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToNoncontrollingInterest_2b23d3ed-025d-4e88-bd73-d76fdba2db22" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_NoncontrollingInterestRollForward_3201d144-b943-4f1a-aad3-c9398e437486" xlink:to="loc_us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToNoncontrollingInterest_2b23d3ed-025d-4e88-bd73-d76fdba2db22" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoncontrollingInterestDecreaseFromDeconsolidation_a1ea9adf-63b3-4642-84bb-fa7f8aeb37c9" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NoncontrollingInterestDecreaseFromDeconsolidation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_NoncontrollingInterestRollForward_3201d144-b943-4f1a-aad3-c9398e437486" xlink:to="loc_us-gaap_NoncontrollingInterestDecreaseFromDeconsolidation_a1ea9adf-63b3-4642-84bb-fa7f8aeb37c9" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestDecreaseFromRedemptions_742f35f5-4672-4448-95af-a0c86c2368a9" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_MinorityInterestDecreaseFromRedemptions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_NoncontrollingInterestRollForward_3201d144-b943-4f1a-aad3-c9398e437486" xlink:to="loc_us-gaap_MinorityInterestDecreaseFromRedemptions_742f35f5-4672-4448-95af-a0c86c2368a9" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RedeemableNoncontrollingInterestEquityOtherCarryingAmount_a85424d0-f3d6-491c-a351-294cc556c5fe" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RedeemableNoncontrollingInterestEquityOtherCarryingAmount"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestTable_279005b9-2cfa-49c9-b4c4-6db1dfaea763" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_MinorityInterestTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_MinorityInterestLineItems_99016c71-e0c8-481e-909f-4d34e7fd00f0" xlink:to="loc_us-gaap_MinorityInterestTable_279005b9-2cfa-49c9-b4c4-6db1dfaea763" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationAxis_fff5515f-8288-4875-abae-458afb1c5a9b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BalanceSheetLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_MinorityInterestTable_279005b9-2cfa-49c9-b4c4-6db1dfaea763" xlink:to="loc_us-gaap_BalanceSheetLocationAxis_fff5515f-8288-4875-abae-458afb1c5a9b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_fff5515f-8288-4875-abae-458afb1c5a9b_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BalanceSheetLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_fff5515f-8288-4875-abae-458afb1c5a9b" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_fff5515f-8288-4875-abae-458afb1c5a9b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_95bacd22-935d-439c-a0ae-c0d54d278b52" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BalanceSheetLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_fff5515f-8288-4875-abae-458afb1c5a9b" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_95bacd22-935d-439c-a0ae-c0d54d278b52" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_RedeemableNoncontrollingInterestMember_afe0a9b4-527f-470f-8abd-896170fd5ac1" xlink:href="nrg-20201231.xsd#nrg_RedeemableNoncontrollingInterestMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_95bacd22-935d-439c-a0ae-c0d54d278b52" xlink:to="loc_nrg_RedeemableNoncontrollingInterestMember_afe0a9b4-527f-470f-8abd-896170fd5ac1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_f291d32c-da73-4ed8-b06e-226c4d49c27d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_MinorityInterestTable_279005b9-2cfa-49c9-b4c4-6db1dfaea763" xlink:to="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_f291d32c-da73-4ed8-b06e-226c4d49c27d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_f291d32c-da73-4ed8-b06e-226c4d49c27d_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_f291d32c-da73-4ed8-b06e-226c4d49c27d" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_f291d32c-da73-4ed8-b06e-226c4d49c27d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_8329f135-3ffb-456a-b562-a64b260d1b95" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_f291d32c-da73-4ed8-b06e-226c4d49c27d" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_8329f135-3ffb-456a-b562-a64b260d1b95" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_NRGYieldInc.AndZephyrRenewablesMember_86679d0d-b43f-40d9-9dea-da0c0324e374" xlink:href="nrg-20201231.xsd#nrg_NRGYieldInc.AndZephyrRenewablesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_8329f135-3ffb-456a-b562-a64b260d1b95" xlink:to="loc_nrg_NRGYieldInc.AndZephyrRenewablesMember_86679d0d-b43f-40d9-9dea-da0c0324e374" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/RevenueRecognition" xlink:type="simple" xlink:href="nrg-20201231.xsd#RevenueRecognition"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/RevenueRecognition" xlink:type="extended" id="i4e8e4e2f8e2c41adb11a720fbc87eeff_RevenueRecognition"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/RevenueRecognitionTables" xlink:type="simple" xlink:href="nrg-20201231.xsd#RevenueRecognitionTables"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/RevenueRecognitionTables" xlink:type="extended" id="i3fcc6508f2d6484d9fe90c0d5aec7edb_RevenueRecognitionTables"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/RevenueRecognitionDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#RevenueRecognitionDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/RevenueRecognitionDetails" xlink:type="extended" id="i2b02305d107846efb7958874ec34d0eb_RevenueRecognitionDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_13dc0a3e-c8f7-4228-9e24-704323dd2648" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsAccumulatedDeficit_b1cc0a64-5d8a-42f3-b359-82b755045e21" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RetainedEarningsAccumulatedDeficit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_13dc0a3e-c8f7-4228-9e24-704323dd2648" xlink:to="loc_us-gaap_RetainedEarningsAccumulatedDeficit_b1cc0a64-5d8a-42f3-b359-82b755045e21" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleTable_a4b23af4-b7ea-4f97-ae45-af7d10fd2bb1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_13dc0a3e-c8f7-4228-9e24-704323dd2648" xlink:to="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleTable_a4b23af4-b7ea-4f97-ae45-af7d10fd2bb1" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InitialApplicationPeriodCumulativeEffectTransitionAxis_3002dba7-caef-48c7-a4d0-a7ccb8dc7b20" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InitialApplicationPeriodCumulativeEffectTransitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleTable_a4b23af4-b7ea-4f97-ae45-af7d10fd2bb1" xlink:to="loc_us-gaap_InitialApplicationPeriodCumulativeEffectTransitionAxis_3002dba7-caef-48c7-a4d0-a7ccb8dc7b20" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InitialApplicationPeriodCumulativeEffectTransitionDomain_3002dba7-caef-48c7-a4d0-a7ccb8dc7b20_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InitialApplicationPeriodCumulativeEffectTransitionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_InitialApplicationPeriodCumulativeEffectTransitionAxis_3002dba7-caef-48c7-a4d0-a7ccb8dc7b20" xlink:to="loc_us-gaap_InitialApplicationPeriodCumulativeEffectTransitionDomain_3002dba7-caef-48c7-a4d0-a7ccb8dc7b20_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InitialApplicationPeriodCumulativeEffectTransitionDomain_7c311d06-9df9-4560-a1d9-b8840dd7328b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InitialApplicationPeriodCumulativeEffectTransitionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_InitialApplicationPeriodCumulativeEffectTransitionAxis_3002dba7-caef-48c7-a4d0-a7ccb8dc7b20" xlink:to="loc_us-gaap_InitialApplicationPeriodCumulativeEffectTransitionDomain_7c311d06-9df9-4560-a1d9-b8840dd7328b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DifferenceBetweenRevenueGuidanceInEffectBeforeAndAfterTopic606Member_136fdb4f-71e2-4b69-9eaf-1c26095f6566" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DifferenceBetweenRevenueGuidanceInEffectBeforeAndAfterTopic606Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InitialApplicationPeriodCumulativeEffectTransitionDomain_7c311d06-9df9-4560-a1d9-b8840dd7328b" xlink:to="loc_us-gaap_DifferenceBetweenRevenueGuidanceInEffectBeforeAndAfterTopic606Member_136fdb4f-71e2-4b69-9eaf-1c26095f6566" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CumulativeEffectPeriodOfAdoptionAxis_7d09a542-d28d-4ee1-bcf2-779fbb71570c" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_CumulativeEffectPeriodOfAdoptionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleTable_a4b23af4-b7ea-4f97-ae45-af7d10fd2bb1" xlink:to="loc_srt_CumulativeEffectPeriodOfAdoptionAxis_7d09a542-d28d-4ee1-bcf2-779fbb71570c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CumulativeEffectPeriodOfAdoptionDomain_7d09a542-d28d-4ee1-bcf2-779fbb71570c_default" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_CumulativeEffectPeriodOfAdoptionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CumulativeEffectPeriodOfAdoptionAxis_7d09a542-d28d-4ee1-bcf2-779fbb71570c" xlink:to="loc_srt_CumulativeEffectPeriodOfAdoptionDomain_7d09a542-d28d-4ee1-bcf2-779fbb71570c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CumulativeEffectPeriodOfAdoptionDomain_585ef14a-87c1-4bd8-9562-5187156b9c11" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_CumulativeEffectPeriodOfAdoptionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CumulativeEffectPeriodOfAdoptionAxis_7d09a542-d28d-4ee1-bcf2-779fbb71570c" xlink:to="loc_srt_CumulativeEffectPeriodOfAdoptionDomain_585ef14a-87c1-4bd8-9562-5187156b9c11" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CumulativeEffectPeriodOfAdoptionAdjustmentMember_81f9184e-331a-429d-9a69-ed1bb425a149" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_CumulativeEffectPeriodOfAdoptionAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_CumulativeEffectPeriodOfAdoptionDomain_585ef14a-87c1-4bd8-9562-5187156b9c11" xlink:to="loc_srt_CumulativeEffectPeriodOfAdoptionAdjustmentMember_81f9184e-331a-429d-9a69-ed1bb425a149" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/RevenueRecognitionCapacityRevenueDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#RevenueRecognitionCapacityRevenueDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/RevenueRecognitionCapacityRevenueDetails" xlink:type="extended" id="idd22272914dd4aa1b9594ebca9124d25_RevenueRecognitionCapacityRevenueDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_c38bfb39-1104-45fa-bfa1-4844692c2dfe" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_8394e91c-a781-4591-91a0-9462c7d6c7c6" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_c38bfb39-1104-45fa-bfa1-4844692c2dfe" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_8394e91c-a781-4591-91a0-9462c7d6c7c6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_e0a9e7c8-9cec-4b8d-9215-4da1eaf7c3c8" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_c38bfb39-1104-45fa-bfa1-4844692c2dfe" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_e0a9e7c8-9cec-4b8d-9215-4da1eaf7c3c8" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis_d9b5ee4a-d743-457a-9dae-7dd3f8af88cb" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_e0a9e7c8-9cec-4b8d-9215-4da1eaf7c3c8" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis_d9b5ee4a-d743-457a-9dae-7dd3f8af88cb" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/RevenueRecognitionCapacityRevenueDetails_1" xlink:type="simple" xlink:href="nrg-20201231.xsd#RevenueRecognitionCapacityRevenueDetails_1"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/RevenueRecognitionCapacityRevenueDetails_1" xlink:type="extended" id="i1474b9d9141c46848934f0035c452581_RevenueRecognitionCapacityRevenueDetails_1">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_c38bfb39-1104-45fa-bfa1-4844692c2dfe" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_8394e91c-a781-4591-91a0-9462c7d6c7c6" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_c38bfb39-1104-45fa-bfa1-4844692c2dfe" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_8394e91c-a781-4591-91a0-9462c7d6c7c6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_e0a9e7c8-9cec-4b8d-9215-4da1eaf7c3c8" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_c38bfb39-1104-45fa-bfa1-4844692c2dfe" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_e0a9e7c8-9cec-4b8d-9215-4da1eaf7c3c8" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/RevenueRecognitionDisaggregatedRevenuesDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#RevenueRecognitionDisaggregatedRevenuesDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/RevenueRecognitionDisaggregatedRevenuesDetails" xlink:type="extended" id="i08d4dc885c5d4804a6622ba648c727d5_RevenueRecognitionDisaggregatedRevenuesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_6012c4c9-870e-474a-99ca-bfb8bcb85bda" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_d8a7e40a-2b90-4e68-8f44-ab4e1cdb1dd2" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_6012c4c9-870e-474a-99ca-bfb8bcb85bda" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_d8a7e40a-2b90-4e68-8f44-ab4e1cdb1dd2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_UnrealizedGainLossOnDerivativesMarkToMarketEconomicHedgingActivities_f1f9f25e-bd4b-4ae6-a009-2f8d4f0fe69c" xlink:href="nrg-20201231.xsd#nrg_UnrealizedGainLossOnDerivativesMarkToMarketEconomicHedgingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_6012c4c9-870e-474a-99ca-bfb8bcb85bda" xlink:to="loc_nrg_UnrealizedGainLossOnDerivativesMarkToMarketEconomicHedgingActivities_f1f9f25e-bd4b-4ae6-a009-2f8d4f0fe69c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Revenues_22029e7f-dfe6-4fcb-9858-d8f5f061e629" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_Revenues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_6012c4c9-870e-474a-99ca-bfb8bcb85bda" xlink:to="loc_us-gaap_Revenues_22029e7f-dfe6-4fcb-9858-d8f5f061e629" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLeaseIncome_ce80fb4d-794a-4891-8268-ed3ad69b0d8d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeaseLeaseIncome"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_6012c4c9-870e-474a-99ca-bfb8bcb85bda" xlink:to="loc_us-gaap_OperatingLeaseLeaseIncome_ce80fb4d-794a-4891-8268-ed3ad69b0d8d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnrealizedGainLossOnDerivatives_2fcc8c75-80e3-4b45-971a-19a8278b2007" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_UnrealizedGainLossOnDerivatives"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_6012c4c9-870e-474a-99ca-bfb8bcb85bda" xlink:to="loc_us-gaap_UnrealizedGainLossOnDerivatives_2fcc8c75-80e3-4b45-971a-19a8278b2007" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_e18a8c94-eedb-43ed-90da-99feea5610a9" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_6012c4c9-870e-474a-99ca-bfb8bcb85bda" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_e18a8c94-eedb-43ed-90da-99feea5610a9" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_d031fc6b-aa12-4727-9b71-65af8c033603" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_e18a8c94-eedb-43ed-90da-99feea5610a9" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_d031fc6b-aa12-4727-9b71-65af8c033603" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_d031fc6b-aa12-4727-9b71-65af8c033603_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_d031fc6b-aa12-4727-9b71-65af8c033603" xlink:to="loc_us-gaap_SegmentDomain_d031fc6b-aa12-4727-9b71-65af8c033603_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_d4aaac6f-ed72-4047-800c-3339d8c5a31d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_d031fc6b-aa12-4727-9b71-65af8c033603" xlink:to="loc_us-gaap_SegmentDomain_d4aaac6f-ed72-4047-800c-3339d8c5a31d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_TexasSegmentMember_fe430415-7e53-4ad1-a6b5-e0c3c23c5e3b" xlink:href="nrg-20201231.xsd#nrg_TexasSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_d4aaac6f-ed72-4047-800c-3339d8c5a31d" xlink:to="loc_nrg_TexasSegmentMember_fe430415-7e53-4ad1-a6b5-e0c3c23c5e3b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_EastSegmentMember_652ec43d-1941-43e2-a54d-807777113505" xlink:href="nrg-20201231.xsd#nrg_EastSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_d4aaac6f-ed72-4047-800c-3339d8c5a31d" xlink:to="loc_nrg_EastSegmentMember_652ec43d-1941-43e2-a54d-807777113505" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_WestAndOtherSegmentMember_06ab2cf2-f3a7-4d77-a47d-5f268dc1bc8f" xlink:href="nrg-20201231.xsd#nrg_WestAndOtherSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_d4aaac6f-ed72-4047-800c-3339d8c5a31d" xlink:to="loc_nrg_WestAndOtherSegmentMember_06ab2cf2-f3a7-4d77-a47d-5f268dc1bc8f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_b3a91bda-b65f-409f-9db7-aec5bbec2260" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_e18a8c94-eedb-43ed-90da-99feea5610a9" xlink:to="loc_srt_ConsolidationItemsAxis_b3a91bda-b65f-409f-9db7-aec5bbec2260" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_b3a91bda-b65f-409f-9db7-aec5bbec2260_default" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_b3a91bda-b65f-409f-9db7-aec5bbec2260" xlink:to="loc_srt_ConsolidationItemsDomain_b3a91bda-b65f-409f-9db7-aec5bbec2260_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_dbe1996e-9f8b-420f-8ded-d88916f06af7" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_b3a91bda-b65f-409f-9db7-aec5bbec2260" xlink:to="loc_srt_ConsolidationItemsDomain_dbe1996e-9f8b-420f-8ded-d88916f06af7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_bec6fbb8-d6e8-4879-9300-58ee8631e4c0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_dbe1996e-9f8b-420f-8ded-d88916f06af7" xlink:to="loc_us-gaap_OperatingSegmentsMember_bec6fbb8-d6e8-4879-9300-58ee8631e4c0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IntersegmentEliminationMember_5c97db15-2c23-4fbf-b20a-51d003dd8acd" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IntersegmentEliminationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_dbe1996e-9f8b-420f-8ded-d88916f06af7" xlink:to="loc_us-gaap_IntersegmentEliminationMember_5c97db15-2c23-4fbf-b20a-51d003dd8acd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_ad2060d7-7a5f-4b69-b592-bf814aac32ce" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_e18a8c94-eedb-43ed-90da-99feea5610a9" xlink:to="loc_srt_ProductOrServiceAxis_ad2060d7-7a5f-4b69-b592-bf814aac32ce" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_ad2060d7-7a5f-4b69-b592-bf814aac32ce_default" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_ad2060d7-7a5f-4b69-b592-bf814aac32ce" xlink:to="loc_srt_ProductsAndServicesDomain_ad2060d7-7a5f-4b69-b592-bf814aac32ce_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_24c06a25-f8d8-4e94-bb93-2c38bb652eef" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_ad2060d7-7a5f-4b69-b592-bf814aac32ce" xlink:to="loc_srt_ProductsAndServicesDomain_24c06a25-f8d8-4e94-bb93-2c38bb652eef" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_ProductsAndServicesRetailRevenueMember_36ae09e0-ced7-44e3-b1ee-de2bdb79b735" xlink:href="nrg-20201231.xsd#nrg_ProductsAndServicesRetailRevenueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_24c06a25-f8d8-4e94-bb93-2c38bb652eef" xlink:to="loc_nrg_ProductsAndServicesRetailRevenueMember_36ae09e0-ced7-44e3-b1ee-de2bdb79b735" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_ProductsAndServicesTotalRetailMember_9b86852f-6677-43fe-8e1f-e400b0df791e" xlink:href="nrg-20201231.xsd#nrg_ProductsAndServicesTotalRetailMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_24c06a25-f8d8-4e94-bb93-2c38bb652eef" xlink:to="loc_nrg_ProductsAndServicesTotalRetailMember_9b86852f-6677-43fe-8e1f-e400b0df791e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_EnergyRevenueMember_ee95ea61-a70c-404b-af33-f04e603d067e" xlink:href="nrg-20201231.xsd#nrg_EnergyRevenueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_24c06a25-f8d8-4e94-bb93-2c38bb652eef" xlink:to="loc_nrg_EnergyRevenueMember_ee95ea61-a70c-404b-af33-f04e603d067e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_CapacityRevenueMember_06e81e3c-4072-4688-8c88-ec106164925b" xlink:href="nrg-20201231.xsd#nrg_CapacityRevenueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_24c06a25-f8d8-4e94-bb93-2c38bb652eef" xlink:to="loc_nrg_CapacityRevenueMember_06e81e3c-4072-4688-8c88-ec106164925b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_ProductsAndServicesDerivativeRevenueMember_e60f548b-f39a-473f-b4bb-f68d24fdae6a" xlink:href="nrg-20201231.xsd#nrg_ProductsAndServicesDerivativeRevenueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_24c06a25-f8d8-4e94-bb93-2c38bb652eef" xlink:to="loc_nrg_ProductsAndServicesDerivativeRevenueMember_e60f548b-f39a-473f-b4bb-f68d24fdae6a" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_ProductsAndServicesOtherMember_13d6e0b0-f72c-49b5-8157-d140d165b9fa" xlink:href="nrg-20201231.xsd#nrg_ProductsAndServicesOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_24c06a25-f8d8-4e94-bb93-2c38bb652eef" xlink:to="loc_nrg_ProductsAndServicesOtherMember_13d6e0b0-f72c-49b5-8157-d140d165b9fa" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_OperatingRevenuesMember_cb282ded-2172-4c67-bbf2-45a8378f68b2" xlink:href="nrg-20201231.xsd#nrg_OperatingRevenuesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_24c06a25-f8d8-4e94-bb93-2c38bb652eef" xlink:to="loc_nrg_OperatingRevenuesMember_cb282ded-2172-4c67-bbf2-45a8378f68b2" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_ProductsAndServicesOtherDerivativeRevenueMember_d46e2977-ee8a-4ebd-aa3c-ea76a51ce8be" xlink:href="nrg-20201231.xsd#nrg_ProductsAndServicesOtherDerivativeRevenueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_24c06a25-f8d8-4e94-bb93-2c38bb652eef" xlink:to="loc_nrg_ProductsAndServicesOtherDerivativeRevenueMember_d46e2977-ee8a-4ebd-aa3c-ea76a51ce8be" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MajorCustomersAxis_f8f13312-d597-4b23-b882-72f509ca43a9" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_MajorCustomersAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_e18a8c94-eedb-43ed-90da-99feea5610a9" xlink:to="loc_srt_MajorCustomersAxis_f8f13312-d597-4b23-b882-72f509ca43a9" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NameOfMajorCustomerDomain_f8f13312-d597-4b23-b882-72f509ca43a9_default" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_NameOfMajorCustomerDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_MajorCustomersAxis_f8f13312-d597-4b23-b882-72f509ca43a9" xlink:to="loc_srt_NameOfMajorCustomerDomain_f8f13312-d597-4b23-b882-72f509ca43a9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NameOfMajorCustomerDomain_a386b127-a2da-455b-8595-97caff61a881" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_NameOfMajorCustomerDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_MajorCustomersAxis_f8f13312-d597-4b23-b882-72f509ca43a9" xlink:to="loc_srt_NameOfMajorCustomerDomain_a386b127-a2da-455b-8595-97caff61a881" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_MassCustomerMember_deda4e6e-c53f-4704-989c-0f01883c084c" xlink:href="nrg-20201231.xsd#nrg_MassCustomerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_a386b127-a2da-455b-8595-97caff61a881" xlink:to="loc_nrg_MassCustomerMember_deda4e6e-c53f-4704-989c-0f01883c084c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_BusinessSolutionsCustomersMember_fb95d819-65b8-4e5c-a970-a7f912c70b97" xlink:href="nrg-20201231.xsd#nrg_BusinessSolutionsCustomersMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_a386b127-a2da-455b-8595-97caff61a881" xlink:to="loc_nrg_BusinessSolutionsCustomersMember_fb95d819-65b8-4e5c-a970-a7f912c70b97" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/RevenueRecognitionContractBalancesDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#RevenueRecognitionContractBalancesDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/RevenueRecognitionContractBalancesDetails" xlink:type="extended" id="icb389432ca1d42659a4dc068725eca90_RevenueRecognitionContractBalancesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_nrg_ScheduleOfContractAssetsAndLiabilitiesLineItems_2d5e5eef-0b18-4ab0-aadf-45a281523f50" xlink:href="nrg-20201231.xsd#nrg_ScheduleOfContractAssetsAndLiabilitiesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalizedContractCostNet_9aa722aa-7f3f-4468-9763-364cfc0fe088" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CapitalizedContractCostNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_ScheduleOfContractAssetsAndLiabilitiesLineItems_2d5e5eef-0b18-4ab0-aadf-45a281523f50" xlink:to="loc_us-gaap_CapitalizedContractCostNet_9aa722aa-7f3f-4468-9763-364cfc0fe088" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableNet_0955748e-0e2e-48cc-9b82-892d3c706599" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccountsReceivableNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_ScheduleOfContractAssetsAndLiabilitiesLineItems_2d5e5eef-0b18-4ab0-aadf-45a281523f50" xlink:to="loc_us-gaap_AccountsReceivableNet_0955748e-0e2e-48cc-9b82-892d3c706599" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnbilledContractsReceivable_0b0c0757-0972-4e88-833e-b74b30ba4cf9" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_UnbilledContractsReceivable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_ScheduleOfContractAssetsAndLiabilitiesLineItems_2d5e5eef-0b18-4ab0-aadf-45a281523f50" xlink:to="loc_us-gaap_UnbilledContractsReceivable_0b0c0757-0972-4e88-833e-b74b30ba4cf9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiability_fdc24273-71d4-4e35-b5a8-b55ad82b28da" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ContractWithCustomerLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_ScheduleOfContractAssetsAndLiabilitiesLineItems_2d5e5eef-0b18-4ab0-aadf-45a281523f50" xlink:to="loc_us-gaap_ContractWithCustomerLiability_fdc24273-71d4-4e35-b5a8-b55ad82b28da" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_ContractwithCustomerLiabilityIncreaseForCashPaymentsReceived_f828c3a5-69b5-466f-a29c-f75ce35fc012" xlink:href="nrg-20201231.xsd#nrg_ContractwithCustomerLiabilityIncreaseForCashPaymentsReceived"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_ScheduleOfContractAssetsAndLiabilitiesLineItems_2d5e5eef-0b18-4ab0-aadf-45a281523f50" xlink:to="loc_nrg_ContractwithCustomerLiabilityIncreaseForCashPaymentsReceived_f828c3a5-69b5-466f-a29c-f75ce35fc012" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiabilityRevenueRecognized_2e885ce6-2716-46c7-b2ee-37843db8ac6a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ContractWithCustomerLiabilityRevenueRecognized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_ScheduleOfContractAssetsAndLiabilitiesLineItems_2d5e5eef-0b18-4ab0-aadf-45a281523f50" xlink:to="loc_us-gaap_ContractWithCustomerLiabilityRevenueRecognized_2e885ce6-2716-46c7-b2ee-37843db8ac6a" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_ScheduleOfContractAssetsAndLiabilitiesTable_daea1094-5549-4aa3-a1c2-3d3ed9c23daf" xlink:href="nrg-20201231.xsd#nrg_ScheduleOfContractAssetsAndLiabilitiesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_nrg_ScheduleOfContractAssetsAndLiabilitiesLineItems_2d5e5eef-0b18-4ab0-aadf-45a281523f50" xlink:to="loc_nrg_ScheduleOfContractAssetsAndLiabilitiesTable_daea1094-5549-4aa3-a1c2-3d3ed9c23daf" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_9e7f8679-7297-4938-bf5c-f3e6d70bb745" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_nrg_ScheduleOfContractAssetsAndLiabilitiesTable_daea1094-5549-4aa3-a1c2-3d3ed9c23daf" xlink:to="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_9e7f8679-7297-4938-bf5c-f3e6d70bb745" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReceivableTypeDomain_9e7f8679-7297-4938-bf5c-f3e6d70bb745_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ReceivableTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_9e7f8679-7297-4938-bf5c-f3e6d70bb745" xlink:to="loc_us-gaap_ReceivableTypeDomain_9e7f8679-7297-4938-bf5c-f3e6d70bb745_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReceivableTypeDomain_31fd60be-e68e-4603-a52b-72e9a915b679" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ReceivableTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_9e7f8679-7297-4938-bf5c-f3e6d70bb745" xlink:to="loc_us-gaap_ReceivableTypeDomain_31fd60be-e68e-4603-a52b-72e9a915b679" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerContractsMember_f5e56b22-f307-4b82-a97b-1fcc8c10d864" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CustomerContractsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReceivableTypeDomain_31fd60be-e68e-4603-a52b-72e9a915b679" xlink:to="loc_us-gaap_CustomerContractsMember_f5e56b22-f307-4b82-a97b-1fcc8c10d864" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeMember_6afcbffc-8b81-45f5-9c5a-b09f46d3dab8" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReceivableTypeDomain_31fd60be-e68e-4603-a52b-72e9a915b679" xlink:to="loc_us-gaap_DerivativeMember_6afcbffc-8b81-45f5-9c5a-b09f46d3dab8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_AffiliatedEntityMember_cd73ab78-b205-493a-8db6-83fbffbfa97c" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_AffiliatedEntityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReceivableTypeDomain_31fd60be-e68e-4603-a52b-72e9a915b679" xlink:to="loc_srt_AffiliatedEntityMember_cd73ab78-b205-493a-8db6-83fbffbfa97c" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/AcquisitionsDiscontinuedOperationsandDispositionsAcquisitionsDiscontinuedOperationsandDispositions" xlink:type="simple" xlink:href="nrg-20201231.xsd#AcquisitionsDiscontinuedOperationsandDispositionsAcquisitionsDiscontinuedOperationsandDispositions"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/AcquisitionsDiscontinuedOperationsandDispositionsAcquisitionsDiscontinuedOperationsandDispositions" xlink:type="extended" id="i3ca3a70b546640df8e1d9a3e86bb15e1_AcquisitionsDiscontinuedOperationsandDispositionsAcquisitionsDiscontinuedOperationsandDispositions"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/AcquisitionsDiscontinuedOperationsandDispositionsTables" xlink:type="simple" xlink:href="nrg-20201231.xsd#AcquisitionsDiscontinuedOperationsandDispositionsTables"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/AcquisitionsDiscontinuedOperationsandDispositionsTables" xlink:type="extended" id="ib00af3a37e65492bb968861e2ebb07a2_AcquisitionsDiscontinuedOperationsandDispositionsTables"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/AcquisitionsDiscontinuedOperationsandDispositionsAcquisitionsDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#AcquisitionsDiscontinuedOperationsandDispositionsAcquisitionsDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/AcquisitionsDiscontinuedOperationsandDispositionsAcquisitionsDetails" xlink:type="extended" id="ic3d0299034f1499aa6c0704bcf2dc467_AcquisitionsDiscontinuedOperationsandDispositionsAcquisitionsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_94463aa8-b34b-46ea-a084-fe505b277124" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NumberOfStatesInWhichEntityOperates_7341974e-95ca-4206-b697-b79847269ef5" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NumberOfStatesInWhichEntityOperates"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_94463aa8-b34b-46ea-a084-fe505b277124" xlink:to="loc_us-gaap_NumberOfStatesInWhichEntityOperates_7341974e-95ca-4206-b697-b79847269ef5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_NumberOfProvincesInWhichEntityOperates_303cd85b-f042-4a36-83f3-78be47498876" xlink:href="nrg-20201231.xsd#nrg_NumberOfProvincesInWhichEntityOperates"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_94463aa8-b34b-46ea-a084-fe505b277124" xlink:to="loc_nrg_NumberOfProvincesInWhichEntityOperates_303cd85b-f042-4a36-83f3-78be47498876" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_NumberOfCustomers_fe05a2fd-68ab-480f-a47c-5eb927595944" xlink:href="nrg-20201231.xsd#nrg_NumberOfCustomers"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_94463aa8-b34b-46ea-a084-fe505b277124" xlink:to="loc_nrg_NumberOfCustomers_fe05a2fd-68ab-480f-a47c-5eb927595944" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferred1_771bcddc-f8c4-4c6e-bb29-08767f8a2f47" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationConsiderationTransferred1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_94463aa8-b34b-46ea-a084-fe505b277124" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferred1_771bcddc-f8c4-4c6e-bb29-08767f8a2f47" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentConsiderationTransferred_09b0b4be-8c5f-4a76-981e-8db629f4efcd" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentConsiderationTransferred"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_94463aa8-b34b-46ea-a084-fe505b277124" xlink:to="loc_us-gaap_BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentConsiderationTransferred_09b0b4be-8c5f-4a76-981e-8db629f4efcd" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireBusinessesGross_09793ee3-4bc5-4cf7-bdc3-2c74133ffdf8" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PaymentsToAcquireBusinessesGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_94463aa8-b34b-46ea-a084-fe505b277124" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesGross_09793ee3-4bc5-4cf7-bdc3-2c74133ffdf8" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromLongTermLinesOfCredit_8a222397-34c6-4447-9432-89d654918242" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ProceedsFromLongTermLinesOfCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_94463aa8-b34b-46ea-a084-fe505b277124" xlink:to="loc_us-gaap_ProceedsFromLongTermLinesOfCredit_8a222397-34c6-4447-9432-89d654918242" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationAcquisitionRelatedCosts_c9354298-ef46-4376-8eb2-4a21b6ac0848" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationAcquisitionRelatedCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_94463aa8-b34b-46ea-a084-fe505b277124" xlink:to="loc_us-gaap_BusinessCombinationAcquisitionRelatedCosts_c9354298-ef46-4376-8eb2-4a21b6ac0848" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromIssuanceOfLongTermDebt_534b7fff-d3dc-41bb-87ef-1b8a1a189c2b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ProceedsFromIssuanceOfLongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_94463aa8-b34b-46ea-a084-fe505b277124" xlink:to="loc_us-gaap_ProceedsFromIssuanceOfLongTermDebt_534b7fff-d3dc-41bb-87ef-1b8a1a189c2b" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_PaymentForAssetAcquisition_ffc80238-27b5-4de5-a4ab-0eeb7210112d" xlink:href="nrg-20201231.xsd#nrg_PaymentForAssetAcquisition"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_94463aa8-b34b-46ea-a084-fe505b277124" xlink:to="loc_nrg_PaymentForAssetAcquisition_ffc80238-27b5-4de5-a4ab-0eeb7210112d" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseExpense_e0b6c75d-2eeb-4f62-9859-7c5e653eea1a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeaseExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_94463aa8-b34b-46ea-a084-fe505b277124" xlink:to="loc_us-gaap_OperatingLeaseExpense_e0b6c75d-2eeb-4f62-9859-7c5e653eea1a" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiability_74e6e656-169c-4629-ac12-0ddb4c9d1157" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeaseLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_94463aa8-b34b-46ea-a084-fe505b277124" xlink:to="loc_us-gaap_OperatingLeaseLiability_74e6e656-169c-4629-ac12-0ddb4c9d1157" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_BusinessAcquisitionConsiderationTransferredWorkingCapitalAndOtherAdjustments_99ff7ced-b25d-4d3b-8207-c1b6e202bda8" xlink:href="nrg-20201231.xsd#nrg_BusinessAcquisitionConsiderationTransferredWorkingCapitalAndOtherAdjustments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_94463aa8-b34b-46ea-a084-fe505b277124" xlink:to="loc_nrg_BusinessAcquisitionConsiderationTransferredWorkingCapitalAndOtherAdjustments_99ff7ced-b25d-4d3b-8207-c1b6e202bda8" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_BusinessAcquisitionResidentialCustomerEquivalentsAcquired_25b97546-ab13-4c98-903f-943e6c3b8982" xlink:href="nrg-20201231.xsd#nrg_BusinessAcquisitionResidentialCustomerEquivalentsAcquired"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_94463aa8-b34b-46ea-a084-fe505b277124" xlink:to="loc_nrg_BusinessAcquisitionResidentialCustomerEquivalentsAcquired_25b97546-ab13-4c98-903f-943e6c3b8982" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_BusinessAcquisitionCustomersAcquired_aa36dacb-cd29-4304-95d4-f1c81e1db1f2" xlink:href="nrg-20201231.xsd#nrg_BusinessAcquisitionCustomersAcquired"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_94463aa8-b34b-46ea-a084-fe505b277124" xlink:to="loc_nrg_BusinessAcquisitionCustomersAcquired_aa36dacb-cd29-4304-95d4-f1c81e1db1f2" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_bffa4eab-b160-40ea-9783-6d6db17900c3" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_94463aa8-b34b-46ea-a084-fe505b277124" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_bffa4eab-b160-40ea-9783-6d6db17900c3" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_422417d8-9e97-4728-ba11-c8685fa32104" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_bffa4eab-b160-40ea-9783-6d6db17900c3" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_422417d8-9e97-4728-ba11-c8685fa32104" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_422417d8-9e97-4728-ba11-c8685fa32104_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_422417d8-9e97-4728-ba11-c8685fa32104" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_422417d8-9e97-4728-ba11-c8685fa32104_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_3dc9f13f-06ad-464f-ba9c-efe3481df6a7" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_422417d8-9e97-4728-ba11-c8685fa32104" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_3dc9f13f-06ad-464f-ba9c-efe3481df6a7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_be9bfdbd-2cfd-4c3a-885f-e138561348a6" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_3dc9f13f-06ad-464f-ba9c-efe3481df6a7" xlink:to="loc_us-gaap_SubsequentEventMember_be9bfdbd-2cfd-4c3a-885f-e138561348a6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_cf7d91da-d7e5-451a-a460-ae9d302324fe" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_bffa4eab-b160-40ea-9783-6d6db17900c3" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_cf7d91da-d7e5-451a-a460-ae9d302324fe" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_cf7d91da-d7e5-451a-a460-ae9d302324fe_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_cf7d91da-d7e5-451a-a460-ae9d302324fe" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_cf7d91da-d7e5-451a-a460-ae9d302324fe_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_6c226fac-4050-428b-9154-04f5dbff710a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_cf7d91da-d7e5-451a-a460-ae9d302324fe" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_6c226fac-4050-428b-9154-04f5dbff710a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_DirectEnergyMember_4f614ce6-5358-47f6-beba-d39d5648f4ae" xlink:href="nrg-20201231.xsd#nrg_DirectEnergyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_6c226fac-4050-428b-9154-04f5dbff710a" xlink:to="loc_nrg_DirectEnergyMember_4f614ce6-5358-47f6-beba-d39d5648f4ae" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_StreamEnergyAcquisitionMember_c30f9e1c-79f8-4a49-ba0a-8af5efca33b2" xlink:href="nrg-20201231.xsd#nrg_StreamEnergyAcquisitionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_6c226fac-4050-428b-9154-04f5dbff710a" xlink:to="loc_nrg_StreamEnergyAcquisitionMember_c30f9e1c-79f8-4a49-ba0a-8af5efca33b2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_XOOMEnergyLLCMember_2f30d1d5-7af2-40f5-a01d-10690e12d475" xlink:href="nrg-20201231.xsd#nrg_XOOMEnergyLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_6c226fac-4050-428b-9154-04f5dbff710a" xlink:to="loc_nrg_XOOMEnergyLLCMember_2f30d1d5-7af2-40f5-a01d-10690e12d475" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_SmallBookAcquisitions2020Member_5406204b-f78a-46ef-970d-379a79faf5cd" xlink:href="nrg-20201231.xsd#nrg_SmallBookAcquisitions2020Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_6c226fac-4050-428b-9154-04f5dbff710a" xlink:to="loc_nrg_SmallBookAcquisitions2020Member_5406204b-f78a-46ef-970d-379a79faf5cd" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_SmallBookAcquisitions2019Member_a1f38ee2-1cc9-4230-99c8-5ccbec99c07b" xlink:href="nrg-20201231.xsd#nrg_SmallBookAcquisitions2019Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_6c226fac-4050-428b-9154-04f5dbff710a" xlink:to="loc_nrg_SmallBookAcquisitions2019Member_a1f38ee2-1cc9-4230-99c8-5ccbec99c07b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_SmallBookAcquisitions2018Member_fb3dceac-9ea3-4889-90f2-454c6b0c3753" xlink:href="nrg-20201231.xsd#nrg_SmallBookAcquisitions2018Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_6c226fac-4050-428b-9154-04f5dbff710a" xlink:to="loc_nrg_SmallBookAcquisitions2018Member_fb3dceac-9ea3-4889-90f2-454c6b0c3753" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_33e2a8dd-41dc-4042-b21a-06604ece8de6" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_bffa4eab-b160-40ea-9783-6d6db17900c3" xlink:to="loc_srt_StatementGeographicalAxis_33e2a8dd-41dc-4042-b21a-06604ece8de6" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_33e2a8dd-41dc-4042-b21a-06604ece8de6_default" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_33e2a8dd-41dc-4042-b21a-06604ece8de6" xlink:to="loc_srt_SegmentGeographicalDomain_33e2a8dd-41dc-4042-b21a-06604ece8de6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_61abb517-5802-428f-a628-b1e49a5f4c89" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_33e2a8dd-41dc-4042-b21a-06604ece8de6" xlink:to="loc_srt_SegmentGeographicalDomain_61abb517-5802-428f-a628-b1e49a5f4c89" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_US_44f347f0-dee7-4927-a256-31edcd13fc2b" xlink:href="https://xbrl.sec.gov/country/2020/country-2020-01-31.xsd#country_US"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_61abb517-5802-428f-a628-b1e49a5f4c89" xlink:to="loc_country_US_44f347f0-dee7-4927-a256-31edcd13fc2b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_CA_3c4f3f43-84ca-4a2c-a766-e4e41c2fbb87" xlink:href="https://xbrl.sec.gov/country/2020/country-2020-01-31.xsd#country_CA"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_61abb517-5802-428f-a628-b1e49a5f4c89" xlink:to="loc_country_CA_3c4f3f43-84ca-4a2c-a766-e4e41c2fbb87" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_AssetAcquisitionAxis_a1e40d7b-0801-46b4-b449-23e6d88c8d9f" xlink:href="nrg-20201231.xsd#nrg_AssetAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_bffa4eab-b160-40ea-9783-6d6db17900c3" xlink:to="loc_nrg_AssetAcquisitionAxis_a1e40d7b-0801-46b4-b449-23e6d88c8d9f" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_AssetAcquisitionDomain_a1e40d7b-0801-46b4-b449-23e6d88c8d9f_default" xlink:href="nrg-20201231.xsd#nrg_AssetAcquisitionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_nrg_AssetAcquisitionAxis_a1e40d7b-0801-46b4-b449-23e6d88c8d9f" xlink:to="loc_nrg_AssetAcquisitionDomain_a1e40d7b-0801-46b4-b449-23e6d88c8d9f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_AssetAcquisitionDomain_16e884b1-e6f6-4279-9097-d607bedcec09" xlink:href="nrg-20201231.xsd#nrg_AssetAcquisitionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_nrg_AssetAcquisitionAxis_a1e40d7b-0801-46b4-b449-23e6d88c8d9f" xlink:to="loc_nrg_AssetAcquisitionDomain_16e884b1-e6f6-4279-9097-d607bedcec09" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_PowertonFacilityAndUnits7And8OfTheJolietFacilityMember_3a754ee5-be2b-4690-b4a9-dbadb3ca248e" xlink:href="nrg-20201231.xsd#nrg_PowertonFacilityAndUnits7And8OfTheJolietFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_AssetAcquisitionDomain_16e884b1-e6f6-4279-9097-d607bedcec09" xlink:to="loc_nrg_PowertonFacilityAndUnits7And8OfTheJolietFacilityMember_3a754ee5-be2b-4690-b4a9-dbadb3ca248e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_aaf693a4-6db7-418a-8165-e93b6662ed95" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_bffa4eab-b160-40ea-9783-6d6db17900c3" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_aaf693a4-6db7-418a-8165-e93b6662ed95" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_aaf693a4-6db7-418a-8165-e93b6662ed95_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_aaf693a4-6db7-418a-8165-e93b6662ed95" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_aaf693a4-6db7-418a-8165-e93b6662ed95_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_9812c2aa-29b9-4354-9fca-b56ade63d777" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_aaf693a4-6db7-418a-8165-e93b6662ed95" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_9812c2aa-29b9-4354-9fca-b56ade63d777" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_LeasedAssetsPowertonFacilityAndUnits7And8OfTheJolietFacilityMember_c6cfdaf1-4a4a-4b37-8fa1-9f88b3793798" xlink:href="nrg-20201231.xsd#nrg_LeasedAssetsPowertonFacilityAndUnits7And8OfTheJolietFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_9812c2aa-29b9-4354-9fca-b56ade63d777" xlink:to="loc_nrg_LeasedAssetsPowertonFacilityAndUnits7And8OfTheJolietFacilityMember_c6cfdaf1-4a4a-4b37-8fa1-9f88b3793798" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/AcquisitionsDiscontinuedOperationsandDispositionsCollectiveCollateralFacilitiesDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#AcquisitionsDiscontinuedOperationsandDispositionsCollectiveCollateralFacilitiesDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/AcquisitionsDiscontinuedOperationsandDispositionsCollectiveCollateralFacilitiesDetails" xlink:type="extended" id="ic84996ba86234eddab9f2f82408bfba7_AcquisitionsDiscontinuedOperationsandDispositionsCollectiveCollateralFacilitiesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityLineItems_f4a9d26b-b591-4a45-b744-251ef88d0ce9" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LineOfCreditFacilityLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentIncreaseDecreaseForPeriodNet_60a89587-e88c-44f6-977f-f41c440b7bb4" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentIncreaseDecreaseForPeriodNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_f4a9d26b-b591-4a45-b744-251ef88d0ce9" xlink:to="loc_us-gaap_DebtInstrumentIncreaseDecreaseForPeriodNet_60a89587-e88c-44f6-977f-f41c440b7bb4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_181f60b3-1f2d-476e-805a-f66416c59c7d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_f4a9d26b-b591-4a45-b744-251ef88d0ce9" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_181f60b3-1f2d-476e-805a-f66416c59c7d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityTable_bb03707d-0a5d-492d-9ad2-7232a7167b04" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LineOfCreditFacilityTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_f4a9d26b-b591-4a45-b744-251ef88d0ce9" xlink:to="loc_us-gaap_LineOfCreditFacilityTable_bb03707d-0a5d-492d-9ad2-7232a7167b04" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_46483fd8-ea45-4491-9591-c1729f2dda2b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_bb03707d-0a5d-492d-9ad2-7232a7167b04" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_46483fd8-ea45-4491-9591-c1729f2dda2b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_46483fd8-ea45-4491-9591-c1729f2dda2b_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_46483fd8-ea45-4491-9591-c1729f2dda2b" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_46483fd8-ea45-4491-9591-c1729f2dda2b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_87cede6b-d3f6-4b31-b5eb-3d557b3b341b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_46483fd8-ea45-4491-9591-c1729f2dda2b" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_87cede6b-d3f6-4b31-b5eb-3d557b3b341b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_16da1acf-25be-4609-9b78-60508425a42a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_87cede6b-d3f6-4b31-b5eb-3d557b3b341b" xlink:to="loc_us-gaap_SubsequentEventMember_16da1acf-25be-4609-9b78-60508425a42a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_e2b6beb1-1169-4ace-a237-7dda5745b884" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_bb03707d-0a5d-492d-9ad2-7232a7167b04" xlink:to="loc_us-gaap_CreditFacilityAxis_e2b6beb1-1169-4ace-a237-7dda5745b884" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_e2b6beb1-1169-4ace-a237-7dda5745b884_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_e2b6beb1-1169-4ace-a237-7dda5745b884" xlink:to="loc_us-gaap_CreditFacilityDomain_e2b6beb1-1169-4ace-a237-7dda5745b884_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_397ab795-b027-4bbb-8934-a773c598c776" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_e2b6beb1-1169-4ace-a237-7dda5745b884" xlink:to="loc_us-gaap_CreditFacilityDomain_397ab795-b027-4bbb-8934-a773c598c776" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_2c3bc80f-8b58-4e92-8fbf-9b20fb0e60e9" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_397ab795-b027-4bbb-8934-a773c598c776" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_2c3bc80f-8b58-4e92-8fbf-9b20fb0e60e9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_4efd2d29-28d9-4406-85c8-e1685d3aa62d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_bb03707d-0a5d-492d-9ad2-7232a7167b04" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_4efd2d29-28d9-4406-85c8-e1685d3aa62d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_4efd2d29-28d9-4406-85c8-e1685d3aa62d_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_4efd2d29-28d9-4406-85c8-e1685d3aa62d" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_4efd2d29-28d9-4406-85c8-e1685d3aa62d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_7d64824a-462d-47c9-bd18-9831ebc57f84" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_4efd2d29-28d9-4406-85c8-e1685d3aa62d" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_7d64824a-462d-47c9-bd18-9831ebc57f84" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_DirectEnergyMember_e35c7f34-487b-40bd-bf26-294682b0330c" xlink:href="nrg-20201231.xsd#nrg_DirectEnergyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_7d64824a-462d-47c9-bd18-9831ebc57f84" xlink:to="loc_nrg_DirectEnergyMember_e35c7f34-487b-40bd-bf26-294682b0330c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_c9809155-c838-4ac4-a063-cd3af295abb7" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_bb03707d-0a5d-492d-9ad2-7232a7167b04" xlink:to="loc_us-gaap_DebtInstrumentAxis_c9809155-c838-4ac4-a063-cd3af295abb7" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_c9809155-c838-4ac4-a063-cd3af295abb7_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_c9809155-c838-4ac4-a063-cd3af295abb7" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_c9809155-c838-4ac4-a063-cd3af295abb7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_2db5f2d7-6dee-4560-ab67-c43a76cb6aba" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_c9809155-c838-4ac4-a063-cd3af295abb7" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_2db5f2d7-6dee-4560-ab67-c43a76cb6aba" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_RevolvingCreditFacilityCommitmentIncreaseMember_ae625eaf-c562-4825-a321-bb9ab62d7c4e" xlink:href="nrg-20201231.xsd#nrg_RevolvingCreditFacilityCommitmentIncreaseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_2db5f2d7-6dee-4560-ab67-c43a76cb6aba" xlink:to="loc_nrg_RevolvingCreditFacilityCommitmentIncreaseMember_ae625eaf-c562-4825-a321-bb9ab62d7c4e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_CreditFacilityNewTrancheMember_e389d155-c10c-47d5-af11-76f3bad8b3ba" xlink:href="nrg-20201231.xsd#nrg_CreditFacilityNewTrancheMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_2db5f2d7-6dee-4560-ab67-c43a76cb6aba" xlink:to="loc_nrg_CreditFacilityNewTrancheMember_e389d155-c10c-47d5-af11-76f3bad8b3ba" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_CreditDefaultSwapFacilityMember_ae37b1c5-0206-416a-8d89-5a88a9f83f23" xlink:href="nrg-20201231.xsd#nrg_CreditDefaultSwapFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_2db5f2d7-6dee-4560-ab67-c43a76cb6aba" xlink:to="loc_nrg_CreditDefaultSwapFacilityMember_ae37b1c5-0206-416a-8d89-5a88a9f83f23" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_ReceivablesFacilityMember_89a87446-2fce-41fa-9554-ebb7b4dfea78" xlink:href="nrg-20201231.xsd#nrg_ReceivablesFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_2db5f2d7-6dee-4560-ab67-c43a76cb6aba" xlink:to="loc_nrg_ReceivablesFacilityMember_89a87446-2fce-41fa-9554-ebb7b4dfea78" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_RepurchaseFacilityMember_bf76e18e-6f95-4764-adec-2ed8b4f42ad2" xlink:href="nrg-20201231.xsd#nrg_RepurchaseFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_2db5f2d7-6dee-4560-ab67-c43a76cb6aba" xlink:to="loc_nrg_RepurchaseFacilityMember_bf76e18e-6f95-4764-adec-2ed8b4f42ad2" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_FacilityAgreementPreCapitalizedTrustSecuritiesMember_a6d1fb82-9921-48dd-86ba-67320a0ac40b" xlink:href="nrg-20201231.xsd#nrg_FacilityAgreementPreCapitalizedTrustSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_2db5f2d7-6dee-4560-ab67-c43a76cb6aba" xlink:to="loc_nrg_FacilityAgreementPreCapitalizedTrustSecuritiesMember_a6d1fb82-9921-48dd-86ba-67320a0ac40b" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_BilateralLetterOfCreditFacilitiesMember_97d9201f-eff7-4987-bfb9-58e8ddcba315" xlink:href="nrg-20201231.xsd#nrg_BilateralLetterOfCreditFacilitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_2db5f2d7-6dee-4560-ab67-c43a76cb6aba" xlink:to="loc_nrg_BilateralLetterOfCreditFacilitiesMember_97d9201f-eff7-4987-bfb9-58e8ddcba315" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_TotalLiquidityAndCollateralFacilitiesMember_124d35dd-ef7e-41d5-bda4-effe83a3f0b4" xlink:href="nrg-20201231.xsd#nrg_TotalLiquidityAndCollateralFacilitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_2db5f2d7-6dee-4560-ab67-c43a76cb6aba" xlink:to="loc_nrg_TotalLiquidityAndCollateralFacilitiesMember_124d35dd-ef7e-41d5-bda4-effe83a3f0b4" xlink:type="arc" order="7"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/AcquisitionsDiscontinuedOperationsandDispositionsDirectEnergyPurchasePriceAllocationDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#AcquisitionsDiscontinuedOperationsandDispositionsDirectEnergyPurchasePriceAllocationDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/AcquisitionsDiscontinuedOperationsandDispositionsDirectEnergyPurchasePriceAllocationDetails" xlink:type="extended" id="i7d698267047e4f2ca65ffb5665ac3599_AcquisitionsDiscontinuedOperationsandDispositionsDirectEnergyPurchasePriceAllocationDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_58fb4bcc-6115-433f-a2f6-8ac4b9eae2e8" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAbstract_36ff2673-fd93-4fe4-9d90-a9e01abeb029" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_58fb4bcc-6115-433f-a2f6-8ac4b9eae2e8" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAbstract_36ff2673-fd93-4fe4-9d90-a9e01abeb029" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents_256778b1-d810-4738-8c33-3f9df75d504b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAbstract_36ff2673-fd93-4fe4-9d90-a9e01abeb029" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents_256778b1-d810-4738-8c33-3f9df75d504b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssets_8bcc4ae0-adf7-445e-b82b-b32cf6bbbf54" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAbstract_36ff2673-fd93-4fe4-9d90-a9e01abeb029" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssets_8bcc4ae0-adf7-445e-b82b-b32cf6bbbf54" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment_7a345848-7595-4bbc-81e7-32d173ae2558" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAbstract_36ff2673-fd93-4fe4-9d90-a9e01abeb029" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment_7a345848-7595-4bbc-81e7-32d173ae2558" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibleAssetsAndGoodwill_9a5cba32-c9fc-44dc-ad99-5c9e4caf2439" xlink:href="nrg-20201231.xsd#nrg_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibleAssetsAndGoodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAbstract_36ff2673-fd93-4fe4-9d90-a9e01abeb029" xlink:to="loc_nrg_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibleAssetsAndGoodwill_9a5cba32-c9fc-44dc-ad99-5c9e4caf2439" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOtherNoncurrentAssets_32902376-d64c-4b82-9c1e-8d2f85a7d288" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOtherNoncurrentAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAbstract_36ff2673-fd93-4fe4-9d90-a9e01abeb029" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOtherNoncurrentAssets_32902376-d64c-4b82-9c1e-8d2f85a7d288" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets_81b2560c-cc3c-4874-b279-f4db3642989e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAbstract_36ff2673-fd93-4fe4-9d90-a9e01abeb029" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets_81b2560c-cc3c-4874-b279-f4db3642989e" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilitiesAbstract_6a95183d-a016-464f-aed3-5f944a7a38b3" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_58fb4bcc-6115-433f-a2f6-8ac4b9eae2e8" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilitiesAbstract_6a95183d-a016-464f-aed3-5f944a7a38b3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilities_10103f0d-8f0e-4f53-ba3e-9ac59efe8d09" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilitiesAbstract_6a95183d-a016-464f-aed3-5f944a7a38b3" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilities_10103f0d-8f0e-4f53-ba3e-9ac59efe8d09" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilities_70752035-1e7c-4a82-b8b4-96aa092749f8" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilitiesAbstract_6a95183d-a016-464f-aed3-5f944a7a38b3" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilities_70752035-1e7c-4a82-b8b4-96aa092749f8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities_86a21426-182b-4651-b2f0-2800e84764cc" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilitiesAbstract_6a95183d-a016-464f-aed3-5f944a7a38b3" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities_86a21426-182b-4651-b2f0-2800e84764cc" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet_67f343c1-afd4-4289-a3e1-cd07a0e58d34" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_58fb4bcc-6115-433f-a2f6-8ac4b9eae2e8" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet_67f343c1-afd4-4289-a3e1-cd07a0e58d34" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_b3031f60-dbde-4190-8d60-1c411660e861" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_58fb4bcc-6115-433f-a2f6-8ac4b9eae2e8" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_b3031f60-dbde-4190-8d60-1c411660e861" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_ddf6bc72-5163-4d44-a465-1ca13d173d51" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_b3031f60-dbde-4190-8d60-1c411660e861" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_ddf6bc72-5163-4d44-a465-1ca13d173d51" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_ddf6bc72-5163-4d44-a465-1ca13d173d51_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_ddf6bc72-5163-4d44-a465-1ca13d173d51" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_ddf6bc72-5163-4d44-a465-1ca13d173d51_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_edd9b265-abc5-44a2-a4f1-3e5a7a08f914" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_ddf6bc72-5163-4d44-a465-1ca13d173d51" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_edd9b265-abc5-44a2-a4f1-3e5a7a08f914" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_DirectEnergyMember_4c4930ce-5692-4c13-aa55-75a45a7e07d1" xlink:href="nrg-20201231.xsd#nrg_DirectEnergyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_edd9b265-abc5-44a2-a4f1-3e5a7a08f914" xlink:to="loc_nrg_DirectEnergyMember_4c4930ce-5692-4c13-aa55-75a45a7e07d1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_f7da5cc4-8d6d-4426-b758-8923858518b0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_b3031f60-dbde-4190-8d60-1c411660e861" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_f7da5cc4-8d6d-4426-b758-8923858518b0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_f7da5cc4-8d6d-4426-b758-8923858518b0_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_f7da5cc4-8d6d-4426-b758-8923858518b0" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_f7da5cc4-8d6d-4426-b758-8923858518b0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_873ac0d0-0de0-4299-90d7-e7a20b9d662e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_f7da5cc4-8d6d-4426-b758-8923858518b0" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_873ac0d0-0de0-4299-90d7-e7a20b9d662e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_8401c051-fb6c-458a-86dc-8b5e49fd2d29" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_873ac0d0-0de0-4299-90d7-e7a20b9d662e" xlink:to="loc_us-gaap_SubsequentEventMember_8401c051-fb6c-458a-86dc-8b5e49fd2d29" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/AcquisitionsDiscontinuedOperationsandDispositionsPurchasePriceAllocationDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#AcquisitionsDiscontinuedOperationsandDispositionsPurchasePriceAllocationDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/AcquisitionsDiscontinuedOperationsandDispositionsPurchasePriceAllocationDetails" xlink:type="extended" id="i78f92bfd5114445884eb4d35a3f5ffde_AcquisitionsDiscontinuedOperationsandDispositionsPurchasePriceAllocationDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_c162df38-c4b6-4f2a-b712-3fd70e3c50a0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables_9ef0dc3b-237b-48e9-841d-e2b44d5b594f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_c162df38-c4b6-4f2a-b712-3fd70e3c50a0" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables_9ef0dc3b-237b-48e9-841d-e2b44d5b594f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesAccountsPayable_2889f3eb-9939-429c-ac3e-8a2b170856ab" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesAccountsPayable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_c162df38-c4b6-4f2a-b712-3fd70e3c50a0" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesAccountsPayable_2889f3eb-9939-429c-ac3e-8a2b170856ab" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedWorkingCapitalOtherNet_bdd3be7d-60e8-4bb5-9211-eb1216434ba2" xlink:href="nrg-20201231.xsd#nrg_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedWorkingCapitalOtherNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_c162df38-c4b6-4f2a-b712-3fd70e3c50a0" xlink:to="loc_nrg_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedWorkingCapitalOtherNet_bdd3be7d-60e8-4bb5-9211-eb1216434ba2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles_876ad063-0618-40b5-947a-ed0911eea8c3" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_c162df38-c4b6-4f2a-b712-3fd70e3c50a0" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles_876ad063-0618-40b5-947a-ed0911eea8c3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_0ccdd0ff-a036-4896-bea3-8812be1b3c4c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_Goodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_c162df38-c4b6-4f2a-b712-3fd70e3c50a0" xlink:to="loc_us-gaap_Goodwill_0ccdd0ff-a036-4896-bea3-8812be1b3c4c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet_c59d120a-71db-48f5-8afa-017b62dfa355" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_c162df38-c4b6-4f2a-b712-3fd70e3c50a0" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet_c59d120a-71db-48f5-8afa-017b62dfa355" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_c08e835f-ade2-40d9-9f42-9d95a53d2e36" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_c162df38-c4b6-4f2a-b712-3fd70e3c50a0" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_c08e835f-ade2-40d9-9f42-9d95a53d2e36" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_da5737cd-2a69-42f0-855d-e515651f97ab" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_c08e835f-ade2-40d9-9f42-9d95a53d2e36" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_da5737cd-2a69-42f0-855d-e515651f97ab" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_da5737cd-2a69-42f0-855d-e515651f97ab_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_da5737cd-2a69-42f0-855d-e515651f97ab" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_da5737cd-2a69-42f0-855d-e515651f97ab_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_c5e3ee28-1558-414c-af6c-c4000bfd326e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_da5737cd-2a69-42f0-855d-e515651f97ab" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_c5e3ee28-1558-414c-af6c-c4000bfd326e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_StreamEnergyAcquisitionMember_f4cb592c-8698-4c7a-85cb-25351170365e" xlink:href="nrg-20201231.xsd#nrg_StreamEnergyAcquisitionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_c5e3ee28-1558-414c-af6c-c4000bfd326e" xlink:to="loc_nrg_StreamEnergyAcquisitionMember_f4cb592c-8698-4c7a-85cb-25351170365e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_XOOMEnergyLLCMember_ddf4843f-946f-456e-a372-e3c8fa701eca" xlink:href="nrg-20201231.xsd#nrg_XOOMEnergyLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_c5e3ee28-1558-414c-af6c-c4000bfd326e" xlink:to="loc_nrg_XOOMEnergyLLCMember_ddf4843f-946f-456e-a372-e3c8fa701eca" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_DirectEnergyMember_03391b7a-2a03-4cfd-8a5a-cdb8f9ab51e6" xlink:href="nrg-20201231.xsd#nrg_DirectEnergyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_c5e3ee28-1558-414c-af6c-c4000bfd326e" xlink:to="loc_nrg_DirectEnergyMember_03391b7a-2a03-4cfd-8a5a-cdb8f9ab51e6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_45fc62b5-57ba-43ff-942b-ac77a06c5f96" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_c08e835f-ade2-40d9-9f42-9d95a53d2e36" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_45fc62b5-57ba-43ff-942b-ac77a06c5f96" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_45fc62b5-57ba-43ff-942b-ac77a06c5f96_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_45fc62b5-57ba-43ff-942b-ac77a06c5f96" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_45fc62b5-57ba-43ff-942b-ac77a06c5f96_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_813d238e-2fc7-4e77-8946-16c3eb1334b4" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_45fc62b5-57ba-43ff-942b-ac77a06c5f96" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_813d238e-2fc7-4e77-8946-16c3eb1334b4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_MarketingPartnershipsMember_e9419c35-5403-4529-a47c-1798f3a21eef" xlink:href="nrg-20201231.xsd#nrg_MarketingPartnershipsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_813d238e-2fc7-4e77-8946-16c3eb1334b4" xlink:to="loc_nrg_MarketingPartnershipsMember_e9419c35-5403-4529-a47c-1798f3a21eef" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerRelationshipsMember_2e7313e2-13a7-4180-aeed-2b62c61538b0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CustomerRelationshipsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_813d238e-2fc7-4e77-8946-16c3eb1334b4" xlink:to="loc_us-gaap_CustomerRelationshipsMember_2e7313e2-13a7-4180-aeed-2b62c61538b0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TradeNamesMember_25a2d18d-7b0d-45ec-a7bf-1802358afc4e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TradeNamesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_813d238e-2fc7-4e77-8946-16c3eb1334b4" xlink:to="loc_us-gaap_TradeNamesMember_25a2d18d-7b0d-45ec-a7bf-1802358afc4e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherIntangibleAssetsMember_fd080c9a-ec48-4221-80b4-88ae47a57afb" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherIntangibleAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_813d238e-2fc7-4e77-8946-16c3eb1334b4" xlink:to="loc_us-gaap_OtherIntangibleAssetsMember_fd080c9a-ec48-4221-80b4-88ae47a57afb" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_fc7bbb1e-7fb8-4e38-8872-e09563152c4b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_c08e835f-ade2-40d9-9f42-9d95a53d2e36" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_fc7bbb1e-7fb8-4e38-8872-e09563152c4b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_fc7bbb1e-7fb8-4e38-8872-e09563152c4b_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_fc7bbb1e-7fb8-4e38-8872-e09563152c4b" xlink:to="loc_us-gaap_SegmentDomain_fc7bbb1e-7fb8-4e38-8872-e09563152c4b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_627d477b-c912-4737-b251-9ffb653bfa47" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_fc7bbb1e-7fb8-4e38-8872-e09563152c4b" xlink:to="loc_us-gaap_SegmentDomain_627d477b-c912-4737-b251-9ffb653bfa47" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_TexasSegmentMember_9a78c15f-e8bb-4299-9a3d-91d4e5dd7656" xlink:href="nrg-20201231.xsd#nrg_TexasSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_627d477b-c912-4737-b251-9ffb653bfa47" xlink:to="loc_nrg_TexasSegmentMember_9a78c15f-e8bb-4299-9a3d-91d4e5dd7656" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_EastSegmentMember_341113f3-6b30-4870-9955-bfb6353c5cc4" xlink:href="nrg-20201231.xsd#nrg_EastSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_627d477b-c912-4737-b251-9ffb653bfa47" xlink:to="loc_nrg_EastSegmentMember_341113f3-6b30-4870-9955-bfb6353c5cc4" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/AcquisitionsDiscontinuedOperationsandDispositionsDiscontinuedOperationsDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#AcquisitionsDiscontinuedOperationsandDispositionsDiscontinuedOperationsDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/AcquisitionsDiscontinuedOperationsandDispositionsDiscontinuedOperationsDetails" xlink:type="extended" id="i73fc52a39b20465db4626c38014e2e61_AcquisitionsDiscontinuedOperationsandDispositionsDiscontinuedOperationsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_8c158659-3ed3-4e50-9245-33db6f229d7d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationConsideration_3db96b3e-97c4-4e22-9641-899d2dadda20" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DisposalGroupIncludingDiscontinuedOperationConsideration"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_8c158659-3ed3-4e50-9245-33db6f229d7d" xlink:to="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationConsideration_3db96b3e-97c4-4e22-9641-899d2dadda20" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_PowerGenerationCapacityMegawatts_d1ec3164-d3b0-4996-85ae-937e2e9b1435" xlink:href="nrg-20201231.xsd#nrg_PowerGenerationCapacityMegawatts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_8c158659-3ed3-4e50-9245-33db6f229d7d" xlink:to="loc_nrg_PowerGenerationCapacityMegawatts_d1ec3164-d3b0-4996-85ae-937e2e9b1435" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherCommitment_0adc3862-edbc-4cbf-90e4-28f491f86314" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherCommitment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_8c158659-3ed3-4e50-9245-33db6f229d7d" xlink:to="loc_us-gaap_OtherCommitment_0adc3862-edbc-4cbf-90e4-28f491f86314" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_DisposalGroupIncludingDiscontinuedOperationOwnershipPercentage_b9024fed-9c9f-475e-bc40-90b234e7293a" xlink:href="nrg-20201231.xsd#nrg_DisposalGroupIncludingDiscontinuedOperationOwnershipPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_8c158659-3ed3-4e50-9245-33db6f229d7d" xlink:to="loc_nrg_DisposalGroupIncludingDiscontinuedOperationOwnershipPercentage_b9024fed-9c9f-475e-bc40-90b234e7293a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_LeaseAndEasementAgreementNumberOfExtensions_f2ed4bf5-aad1-4f4a-a7b2-20dc959cb882" xlink:href="nrg-20201231.xsd#nrg_LeaseAndEasementAgreementNumberOfExtensions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_8c158659-3ed3-4e50-9245-33db6f229d7d" xlink:to="loc_nrg_LeaseAndEasementAgreementNumberOfExtensions_f2ed4bf5-aad1-4f4a-a7b2-20dc959cb882" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseRenewalTerm_bbc41c4e-2f8d-4565-bf71-fe2daaedc4ed" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseRenewalTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_8c158659-3ed3-4e50-9245-33db6f229d7d" xlink:to="loc_us-gaap_LesseeOperatingLeaseRenewalTerm_bbc41c4e-2f8d-4565-bf71-fe2daaedc4ed" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_c44fed37-3c08-4776-ab85-80859f48358f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_8c158659-3ed3-4e50-9245-33db6f229d7d" xlink:to="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_c44fed37-3c08-4776-ab85-80859f48358f" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationAxis_7db9f77d-a76b-4fcc-afe1-ef2c19d4d407" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DisposalGroupClassificationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_c44fed37-3c08-4776-ab85-80859f48358f" xlink:to="loc_us-gaap_DisposalGroupClassificationAxis_7db9f77d-a76b-4fcc-afe1-ef2c19d4d407" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationDomain_7db9f77d-a76b-4fcc-afe1-ef2c19d4d407_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DisposalGroupClassificationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DisposalGroupClassificationAxis_7db9f77d-a76b-4fcc-afe1-ef2c19d4d407" xlink:to="loc_us-gaap_DisposalGroupClassificationDomain_7db9f77d-a76b-4fcc-afe1-ef2c19d4d407_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationDomain_16bb8852-bc05-4e5d-afc1-5723e712bfe6" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DisposalGroupClassificationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DisposalGroupClassificationAxis_7db9f77d-a76b-4fcc-afe1-ef2c19d4d407" xlink:to="loc_us-gaap_DisposalGroupClassificationDomain_16bb8852-bc05-4e5d-afc1-5723e712bfe6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDiscontinuedOperationsMember_076d4854-30ae-47ed-8906-debc3981099e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SegmentDiscontinuedOperationsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupClassificationDomain_16bb8852-bc05-4e5d-afc1-5723e712bfe6" xlink:to="loc_us-gaap_SegmentDiscontinuedOperationsMember_076d4854-30ae-47ed-8906-debc3981099e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_b7b1c79f-f012-40f3-a6cf-731cbc50bc04" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_c44fed37-3c08-4776-ab85-80859f48358f" xlink:to="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_b7b1c79f-f012-40f3-a6cf-731cbc50bc04" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_b7b1c79f-f012-40f3-a6cf-731cbc50bc04_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_b7b1c79f-f012-40f3-a6cf-731cbc50bc04" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_b7b1c79f-f012-40f3-a6cf-731cbc50bc04_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_545533d9-95ad-43dc-9684-e405d79e29f9" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_b7b1c79f-f012-40f3-a6cf-731cbc50bc04" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_545533d9-95ad-43dc-9684-e405d79e29f9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_SouthCentralPortfolioMember_d4d9518d-2926-4b1d-b483-e96a9631011a" xlink:href="nrg-20201231.xsd#nrg_SouthCentralPortfolioMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_545533d9-95ad-43dc-9684-e405d79e29f9" xlink:to="loc_nrg_SouthCentralPortfolioMember_d4d9518d-2926-4b1d-b483-e96a9631011a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_NRGYieldInc.AndZephyrRenewablesMember_77bddb23-f0f8-4c8b-b7d4-d02571ad4b9c" xlink:href="nrg-20201231.xsd#nrg_NRGYieldInc.AndZephyrRenewablesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_545533d9-95ad-43dc-9684-e405d79e29f9" xlink:to="loc_nrg_NRGYieldInc.AndZephyrRenewablesMember_77bddb23-f0f8-4c8b-b7d4-d02571ad4b9c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_CarlsbadEnergyHoldingsLLCMember_e2bf8bb7-91b8-46c3-a6f4-1fbaf2d51e03" xlink:href="nrg-20201231.xsd#nrg_CarlsbadEnergyHoldingsLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_545533d9-95ad-43dc-9684-e405d79e29f9" xlink:to="loc_nrg_CarlsbadEnergyHoldingsLLCMember_e2bf8bb7-91b8-46c3-a6f4-1fbaf2d51e03" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherCommitmentsAxis_827868ac-9e09-487f-bd3e-3d32d503fa66" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherCommitmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_c44fed37-3c08-4776-ab85-80859f48358f" xlink:to="loc_us-gaap_OtherCommitmentsAxis_827868ac-9e09-487f-bd3e-3d32d503fa66" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherCommitmentsDomain_827868ac-9e09-487f-bd3e-3d32d503fa66_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherCommitmentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_OtherCommitmentsAxis_827868ac-9e09-487f-bd3e-3d32d503fa66" xlink:to="loc_us-gaap_OtherCommitmentsDomain_827868ac-9e09-487f-bd3e-3d32d503fa66_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherCommitmentsDomain_99d2e07e-6732-414f-a4bb-eeecfc78027d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherCommitmentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_OtherCommitmentsAxis_827868ac-9e09-487f-bd3e-3d32d503fa66" xlink:to="loc_us-gaap_OtherCommitmentsDomain_99d2e07e-6732-414f-a4bb-eeecfc78027d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_CostToCompleteConstructionMember_19df4b55-ac31-44e4-8702-c27c6e47e812" xlink:href="nrg-20201231.xsd#nrg_CostToCompleteConstructionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherCommitmentsDomain_99d2e07e-6732-414f-a4bb-eeecfc78027d" xlink:to="loc_nrg_CostToCompleteConstructionMember_19df4b55-ac31-44e4-8702-c27c6e47e812" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_PropertyTaxesForSolarPropertiesMember_6578bd3b-c10e-4d47-b85a-ca361e5152b5" xlink:href="nrg-20201231.xsd#nrg_PropertyTaxesForSolarPropertiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherCommitmentsDomain_99d2e07e-6732-414f-a4bb-eeecfc78027d" xlink:to="loc_nrg_PropertyTaxesForSolarPropertiesMember_6578bd3b-c10e-4d47-b85a-ca361e5152b5" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/AcquisitionsDiscontinuedOperationsandDispositionsSummaryofResultsDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#AcquisitionsDiscontinuedOperationsandDispositionsSummaryofResultsDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/AcquisitionsDiscontinuedOperationsandDispositionsSummaryofResultsDetails" xlink:type="extended" id="i5a30e02ce4bd425a9d5a72642a07aa4c_AcquisitionsDiscontinuedOperationsandDispositionsSummaryofResultsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_2c40499d-376c-491e-ad27-03f1f91978c5" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationRevenue_7266d63c-e83d-4bad-bdfc-06ff7d14a39a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DisposalGroupIncludingDiscontinuedOperationRevenue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_2c40499d-376c-491e-ad27-03f1f91978c5" xlink:to="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationRevenue_7266d63c-e83d-4bad-bdfc-06ff7d14a39a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationOperatingExpense_3da0b7c1-b47d-4948-b42c-24f9bdf9876a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DisposalGroupIncludingDiscontinuedOperationOperatingExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_2c40499d-376c-491e-ad27-03f1f91978c5" xlink:to="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationOperatingExpense_3da0b7c1-b47d-4948-b42c-24f9bdf9876a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationOtherIncome_1ab2e674-a28c-4836-a664-11ccd4a3886b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DisposalGroupIncludingDiscontinuedOperationOtherIncome"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_2c40499d-376c-491e-ad27-03f1f91978c5" xlink:to="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationOtherIncome_1ab2e674-a28c-4836-a664-11ccd4a3886b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationOtherExpense_9a9b37a1-cb71-4200-b3a7-1e349501b14a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DisposalGroupIncludingDiscontinuedOperationOtherExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_2c40499d-376c-491e-ad27-03f1f91978c5" xlink:to="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationOtherExpense_9a9b37a1-cb71-4200-b3a7-1e349501b14a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationOperatingIncomeLoss_8ca1905c-53d2-47ba-a3fa-2667cc5f05be" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DisposalGroupIncludingDiscontinuedOperationOperatingIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_2c40499d-376c-491e-ad27-03f1f91978c5" xlink:to="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationOperatingIncomeLoss_8ca1905c-53d2-47ba-a3fa-2667cc5f05be" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DiscontinuedOperationTaxEffectOfDiscontinuedOperation_52ae786e-db90-46de-8995-80fce6cb3a34" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DiscontinuedOperationTaxEffectOfDiscontinuedOperation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_2c40499d-376c-491e-ad27-03f1f91978c5" xlink:to="loc_us-gaap_DiscontinuedOperationTaxEffectOfDiscontinuedOperation_52ae786e-db90-46de-8995-80fce6cb3a34" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationInterestIncome_f87a99c8-5404-41d1-8d35-ccd348de34e1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DisposalGroupIncludingDiscontinuedOperationInterestIncome"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_2c40499d-376c-491e-ad27-03f1f91978c5" xlink:to="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationInterestIncome_f87a99c8-5404-41d1-8d35-ccd348de34e1" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax_16339723-fa23-48c9-9e5e-ea6656570326" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_2c40499d-376c-491e-ad27-03f1f91978c5" xlink:to="loc_us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax_16339723-fa23-48c9-9e5e-ea6656570326" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeconsolidationGainOrLossAmount_bb4f8431-0fef-43a8-aafa-d79862dd649e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeconsolidationGainOrLossAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_2c40499d-376c-491e-ad27-03f1f91978c5" xlink:to="loc_us-gaap_DeconsolidationGainOrLossAmount_bb4f8431-0fef-43a8-aafa-d79862dd649e" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_DisposalGroupIncludingDiscontinuedOperationIncomeExpensePropertyTaxIndemnification_02578998-e8e2-4d26-a8d5-e9127d31649e" xlink:href="nrg-20201231.xsd#nrg_DisposalGroupIncludingDiscontinuedOperationIncomeExpensePropertyTaxIndemnification"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_2c40499d-376c-491e-ad27-03f1f91978c5" xlink:to="loc_nrg_DisposalGroupIncludingDiscontinuedOperationIncomeExpensePropertyTaxIndemnification_02578998-e8e2-4d26-a8d5-e9127d31649e" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_DiscontinuedOperationSettlementConsiderationAndPriorServiceCostCredit_d04e3b51-f622-4e29-9d68-08a7f85c9578" xlink:href="nrg-20201231.xsd#nrg_DiscontinuedOperationSettlementConsiderationAndPriorServiceCostCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_2c40499d-376c-491e-ad27-03f1f91978c5" xlink:to="loc_nrg_DiscontinuedOperationSettlementConsiderationAndPriorServiceCostCredit_d04e3b51-f622-4e29-9d68-08a7f85c9578" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_DiscontinuedOperationPensionLiabilityAssumption_90a4132d-e218-4f22-b6ca-212cf35655ef" xlink:href="nrg-20201231.xsd#nrg_DiscontinuedOperationPensionLiabilityAssumption"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_2c40499d-376c-491e-ad27-03f1f91978c5" xlink:to="loc_nrg_DiscontinuedOperationPensionLiabilityAssumption_90a4132d-e218-4f22-b6ca-212cf35655ef" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_DisposalGroupIncludingDiscontinuedOperationOtherIncomeExpense_bb51db7b-1a6d-4761-ac70-46ff14c57c97" xlink:href="nrg-20201231.xsd#nrg_DisposalGroupIncludingDiscontinuedOperationOtherIncomeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_2c40499d-376c-491e-ad27-03f1f91978c5" xlink:to="loc_nrg_DisposalGroupIncludingDiscontinuedOperationOtherIncomeExpense_bb51db7b-1a6d-4761-ac70-46ff14c57c97" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DiscontinuedOperationGainLossOnDisposalOfDiscontinuedOperationNetOfTax_d84bc3c7-8b30-40c4-b7c4-480b53dcebb2" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DiscontinuedOperationGainLossOnDisposalOfDiscontinuedOperationNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_2c40499d-376c-491e-ad27-03f1f91978c5" xlink:to="loc_us-gaap_DiscontinuedOperationGainLossOnDisposalOfDiscontinuedOperationNetOfTax_d84bc3c7-8b30-40c4-b7c4-480b53dcebb2" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToReportingEntity_a3c36304-aae1-4832-9f7c-6ebf76caf092" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToReportingEntity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_2c40499d-376c-491e-ad27-03f1f91978c5" xlink:to="loc_us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToReportingEntity_a3c36304-aae1-4832-9f7c-6ebf76caf092" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_2a8e4333-f750-4d8a-8f46-d22cb49be8fc" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_2c40499d-376c-491e-ad27-03f1f91978c5" xlink:to="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_2a8e4333-f750-4d8a-8f46-d22cb49be8fc" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationAxis_648c5e7c-d626-4f86-b2e7-808895586380" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DisposalGroupClassificationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_2a8e4333-f750-4d8a-8f46-d22cb49be8fc" xlink:to="loc_us-gaap_DisposalGroupClassificationAxis_648c5e7c-d626-4f86-b2e7-808895586380" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationDomain_648c5e7c-d626-4f86-b2e7-808895586380_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DisposalGroupClassificationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DisposalGroupClassificationAxis_648c5e7c-d626-4f86-b2e7-808895586380" xlink:to="loc_us-gaap_DisposalGroupClassificationDomain_648c5e7c-d626-4f86-b2e7-808895586380_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationDomain_d1e820cb-d829-4f98-a7e9-d83c9bc043f6" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DisposalGroupClassificationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DisposalGroupClassificationAxis_648c5e7c-d626-4f86-b2e7-808895586380" xlink:to="loc_us-gaap_DisposalGroupClassificationDomain_d1e820cb-d829-4f98-a7e9-d83c9bc043f6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDiscontinuedOperationsMember_9a2d66a6-1a71-40cb-b3b5-836fba23f6dc" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SegmentDiscontinuedOperationsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupClassificationDomain_d1e820cb-d829-4f98-a7e9-d83c9bc043f6" xlink:to="loc_us-gaap_SegmentDiscontinuedOperationsMember_9a2d66a6-1a71-40cb-b3b5-836fba23f6dc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_b963e806-cb8d-4dba-b803-20ba569143c2" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_2a8e4333-f750-4d8a-8f46-d22cb49be8fc" xlink:to="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_b963e806-cb8d-4dba-b803-20ba569143c2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_b963e806-cb8d-4dba-b803-20ba569143c2_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_b963e806-cb8d-4dba-b803-20ba569143c2" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_b963e806-cb8d-4dba-b803-20ba569143c2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_3b4156f3-529f-4afc-8597-20ec41eccddd" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_b963e806-cb8d-4dba-b803-20ba569143c2" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_3b4156f3-529f-4afc-8597-20ec41eccddd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_SouthCentralPortfolioMember_dd3fc73e-7e0e-44ea-8845-96ff9d70497f" xlink:href="nrg-20201231.xsd#nrg_SouthCentralPortfolioMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_3b4156f3-529f-4afc-8597-20ec41eccddd" xlink:to="loc_nrg_SouthCentralPortfolioMember_dd3fc73e-7e0e-44ea-8845-96ff9d70497f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_CarlsbadEnergyHoldingsLLCMember_ef5cb8ac-9701-4c05-9938-a8e78a69e35f" xlink:href="nrg-20201231.xsd#nrg_CarlsbadEnergyHoldingsLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_3b4156f3-529f-4afc-8597-20ec41eccddd" xlink:to="loc_nrg_CarlsbadEnergyHoldingsLLCMember_ef5cb8ac-9701-4c05-9938-a8e78a69e35f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_GenOnMember_223edb25-e4fb-4915-8694-4da57b1f6b2c" xlink:href="nrg-20201231.xsd#nrg_GenOnMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_3b4156f3-529f-4afc-8597-20ec41eccddd" xlink:to="loc_nrg_GenOnMember_223edb25-e4fb-4915-8694-4da57b1f6b2c" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/AcquisitionsDiscontinuedOperationsandDispositionsSaleofAssetsPriortoDiscontinuedDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#AcquisitionsDiscontinuedOperationsandDispositionsSaleofAssetsPriortoDiscontinuedDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/AcquisitionsDiscontinuedOperationsandDispositionsSaleofAssetsPriortoDiscontinuedDetails" xlink:type="extended" id="id5aa38ee3b1740d4b84e6097e54859fc_AcquisitionsDiscontinuedOperationsandDispositionsSaleofAssetsPriortoDiscontinuedDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_cfa199bf-d310-4465-8924-7bef197afce7" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationConsideration_d6170af3-281d-4e4d-9a1d-25b9a520e211" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DisposalGroupIncludingDiscontinuedOperationConsideration"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_cfa199bf-d310-4465-8924-7bef197afce7" xlink:to="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationConsideration_d6170af3-281d-4e4d-9a1d-25b9a520e211" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_PercentageofOwnershipSoldofSubsidiary_fc84eec1-2a38-436b-b063-451d749d234d" xlink:href="nrg-20201231.xsd#nrg_PercentageofOwnershipSoldofSubsidiary"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_cfa199bf-d310-4465-8924-7bef197afce7" xlink:to="loc_nrg_PercentageofOwnershipSoldofSubsidiary_fc84eec1-2a38-436b-b063-451d749d234d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_PowerGenerationCapacityMegawatts_c33c08ee-693b-4e94-92ff-5e2bbfd17027" xlink:href="nrg-20201231.xsd#nrg_PowerGenerationCapacityMegawatts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_cfa199bf-d310-4465-8924-7bef197afce7" xlink:to="loc_nrg_PowerGenerationCapacityMegawatts_c33c08ee-693b-4e94-92ff-5e2bbfd17027" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesOfDisposalGroupIncludingDiscontinuedOperation_c177e62d-5b46-41cd-9c43-d8d86d5254e4" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LiabilitiesOfDisposalGroupIncludingDiscontinuedOperation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_cfa199bf-d310-4465-8924-7bef197afce7" xlink:to="loc_us-gaap_LiabilitiesOfDisposalGroupIncludingDiscontinuedOperation_c177e62d-5b46-41cd-9c43-d8d86d5254e4" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_a0ef59c6-62b3-40aa-b724-e64e9d4fc4ee" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_cfa199bf-d310-4465-8924-7bef197afce7" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_a0ef59c6-62b3-40aa-b724-e64e9d4fc4ee" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_25d34139-ac54-4b72-865a-ad294bd6f09c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_a0ef59c6-62b3-40aa-b724-e64e9d4fc4ee" xlink:to="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_25d34139-ac54-4b72-865a-ad294bd6f09c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_25d34139-ac54-4b72-865a-ad294bd6f09c_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_25d34139-ac54-4b72-865a-ad294bd6f09c" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_25d34139-ac54-4b72-865a-ad294bd6f09c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_70a4ac69-fcae-465b-b409-69c0811045b7" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_25d34139-ac54-4b72-865a-ad294bd6f09c" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_70a4ac69-fcae-465b-b409-69c0811045b7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_UPMCThermalProjectMember_81ad4e10-2a40-4511-ad1a-44d7b25ec62b" xlink:href="nrg-20201231.xsd#nrg_UPMCThermalProjectMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_70a4ac69-fcae-465b-b409-69c0811045b7" xlink:to="loc_nrg_UPMCThermalProjectMember_81ad4e10-2a40-4511-ad1a-44d7b25ec62b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_BuckthornRenewablesLLCMember_ffe1266b-948a-4534-8213-4a8af24dace2" xlink:href="nrg-20201231.xsd#nrg_BuckthornRenewablesLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_70a4ac69-fcae-465b-b409-69c0811045b7" xlink:to="loc_nrg_BuckthornRenewablesLLCMember_ffe1266b-948a-4534-8213-4a8af24dace2" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/AcquisitionsDiscontinuedOperationsandDispositionsGenOnSettlementandPlanConfirmationDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#AcquisitionsDiscontinuedOperationsandDispositionsGenOnSettlementandPlanConfirmationDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/AcquisitionsDiscontinuedOperationsandDispositionsGenOnSettlementandPlanConfirmationDetails" xlink:type="extended" id="i963c2d67d8db4d79add7a0392b13588f_AcquisitionsDiscontinuedOperationsandDispositionsGenOnSettlementandPlanConfirmationDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_c1b45ef0-877a-4406-a0f8-b105af8bd910" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_PaymentsToAffiliateSettlementAgreement_915c8d55-ef75-48c9-b6ff-4d2ee9ba95f1" xlink:href="nrg-20201231.xsd#nrg_PaymentsToAffiliateSettlementAgreement"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_c1b45ef0-877a-4406-a0f8-b105af8bd910" xlink:to="loc_nrg_PaymentsToAffiliateSettlementAgreement_915c8d55-ef75-48c9-b6ff-4d2ee9ba95f1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringAndRelatedCostExpectedCost1_d6280716-d51a-4735-af6f-6419fce95131" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RestructuringAndRelatedCostExpectedCost1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_c1b45ef0-877a-4406-a0f8-b105af8bd910" xlink:to="loc_us-gaap_RestructuringAndRelatedCostExpectedCost1_d6280716-d51a-4735-af6f-6419fce95131" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_RestructuringandRelatedCostCreditApplied_865917f7-784c-4887-a6db-681eaa7f6ff2" xlink:href="nrg-20201231.xsd#nrg_RestructuringandRelatedCostCreditApplied"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_c1b45ef0-877a-4406-a0f8-b105af8bd910" xlink:to="loc_nrg_RestructuringandRelatedCostCreditApplied_865917f7-784c-4887-a6db-681eaa7f6ff2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsForAdvanceToAffiliate_2b0be4b9-d315-4e8c-9444-eaefdc4373fe" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PaymentsForAdvanceToAffiliate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_c1b45ef0-877a-4406-a0f8-b105af8bd910" xlink:to="loc_us-gaap_PaymentsForAdvanceToAffiliate_2b0be4b9-d315-4e8c-9444-eaefdc4373fe" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DueFromRelatedParties_269a7566-a55f-4e29-87ce-1375136cc014" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DueFromRelatedParties"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_c1b45ef0-877a-4406-a0f8-b105af8bd910" xlink:to="loc_us-gaap_DueFromRelatedParties_269a7566-a55f-4e29-87ce-1375136cc014" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionDueFromToRelatedParty_690646f0-ba4c-408f-8e93-ba49c266dffc" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RelatedPartyTransactionDueFromToRelatedParty"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_c1b45ef0-877a-4406-a0f8-b105af8bd910" xlink:to="loc_us-gaap_RelatedPartyTransactionDueFromToRelatedParty_690646f0-ba4c-408f-8e93-ba49c266dffc" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLossCarryforwards_e27a8422-5929-44c5-a7a6-56ec1b26fc67" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLossCarryforwards"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_c1b45ef0-877a-4406-a0f8-b105af8bd910" xlink:to="loc_us-gaap_OperatingLossCarryforwards_e27a8422-5929-44c5-a7a6-56ec1b26fc67" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityCurrentBorrowingCapacity_c8c98744-c4fe-4dbf-b044-dd22b99ddcd1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LineOfCreditFacilityCurrentBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_c1b45ef0-877a-4406-a0f8-b105af8bd910" xlink:to="loc_us-gaap_LineOfCreditFacilityCurrentBorrowingCapacity_c8c98744-c4fe-4dbf-b044-dd22b99ddcd1" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfessionalFees_70833c2e-4f00-495a-bc84-053f5b700d5c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ProfessionalFees"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_c1b45ef0-877a-4406-a0f8-b105af8bd910" xlink:to="loc_us-gaap_ProfessionalFees_70833c2e-4f00-495a-bc84-053f5b700d5c" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_9ff00f35-6984-48e3-a093-23f77066d5e3" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_c1b45ef0-877a-4406-a0f8-b105af8bd910" xlink:to="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_9ff00f35-6984-48e3-a093-23f77066d5e3" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_9b13a81f-bf1c-4395-aa71-5bfa9f2cdfc9" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_9ff00f35-6984-48e3-a093-23f77066d5e3" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_9b13a81f-bf1c-4395-aa71-5bfa9f2cdfc9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_9b13a81f-bf1c-4395-aa71-5bfa9f2cdfc9_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_9b13a81f-bf1c-4395-aa71-5bfa9f2cdfc9" xlink:to="loc_us-gaap_RelatedPartyDomain_9b13a81f-bf1c-4395-aa71-5bfa9f2cdfc9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_a83b6747-bdea-4f69-82ef-4d9750d13fb4" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_9b13a81f-bf1c-4395-aa71-5bfa9f2cdfc9" xlink:to="loc_us-gaap_RelatedPartyDomain_a83b6747-bdea-4f69-82ef-4d9750d13fb4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_AffiliatedEntityMember_8de44b18-6d71-4904-8d16-3803299ced58" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_AffiliatedEntityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_a83b6747-bdea-4f69-82ef-4d9750d13fb4" xlink:to="loc_srt_AffiliatedEntityMember_8de44b18-6d71-4904-8d16-3803299ced58" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionAxis_9af1ac42-1356-4551-82cd-288b76643337" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RelatedPartyTransactionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_9ff00f35-6984-48e3-a093-23f77066d5e3" xlink:to="loc_us-gaap_RelatedPartyTransactionAxis_9af1ac42-1356-4551-82cd-288b76643337" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain_9af1ac42-1356-4551-82cd-288b76643337_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RelatedPartyTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis_9af1ac42-1356-4551-82cd-288b76643337" xlink:to="loc_us-gaap_RelatedPartyTransactionDomain_9af1ac42-1356-4551-82cd-288b76643337_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain_074cd5c8-04b8-4f3d-a788-094d677a2644" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RelatedPartyTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis_9af1ac42-1356-4551-82cd-288b76643337" xlink:to="loc_us-gaap_RelatedPartyTransactionDomain_074cd5c8-04b8-4f3d-a788-094d677a2644" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_ServicesAgreementMember_ee36da69-c373-4c7b-8c9c-a9c39a482465" xlink:href="nrg-20201231.xsd#nrg_ServicesAgreementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionDomain_074cd5c8-04b8-4f3d-a788-094d677a2644" xlink:to="loc_nrg_ServicesAgreementMember_ee36da69-c373-4c7b-8c9c-a9c39a482465" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_RevolvingCreditFacilityBorrowingsMember_f1278431-1a6c-4865-894c-072c13cc4e2f" xlink:href="nrg-20201231.xsd#nrg_RevolvingCreditFacilityBorrowingsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionDomain_074cd5c8-04b8-4f3d-a788-094d677a2644" xlink:to="loc_nrg_RevolvingCreditFacilityBorrowingsMember_f1278431-1a6c-4865-894c-072c13cc4e2f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_AccruedInterestOnBorrowingsMember_b1cd4f14-feff-4e25-a9a9-8353db398ca7" xlink:href="nrg-20201231.xsd#nrg_AccruedInterestOnBorrowingsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionDomain_074cd5c8-04b8-4f3d-a788-094d677a2644" xlink:to="loc_nrg_AccruedInterestOnBorrowingsMember_b1cd4f14-feff-4e25-a9a9-8353db398ca7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_ReductionOfSettlementPaymentMember_1a928d6e-9cf6-4220-91e6-1720a793502b" xlink:href="nrg-20201231.xsd#nrg_ReductionOfSettlementPaymentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionDomain_074cd5c8-04b8-4f3d-a788-094d677a2644" xlink:to="loc_nrg_ReductionOfSettlementPaymentMember_1a928d6e-9cf6-4220-91e6-1720a793502b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_AssignmentOfHistoricalClaimsAgainstREMAMember_271fbde1-2424-4307-9dfb-adec5f0e985d" xlink:href="nrg-20201231.xsd#nrg_AssignmentOfHistoricalClaimsAgainstREMAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionDomain_074cd5c8-04b8-4f3d-a788-094d677a2644" xlink:to="loc_nrg_AssignmentOfHistoricalClaimsAgainstREMAMember_271fbde1-2424-4307-9dfb-adec5f0e985d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_OtherMember_99fb6f44-b9dc-4e49-9268-8b4077b5ddf4" xlink:href="nrg-20201231.xsd#nrg_OtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionDomain_074cd5c8-04b8-4f3d-a788-094d677a2644" xlink:to="loc_nrg_OtherMember_99fb6f44-b9dc-4e49-9268-8b4077b5ddf4" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_4f74a528-c304-499a-99a3-55e9fade1aa9" xlink:href="https://xbrl.sec.gov/dei/2020/dei-2020-01-31.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_9ff00f35-6984-48e3-a093-23f77066d5e3" xlink:to="loc_dei_LegalEntityAxis_4f74a528-c304-499a-99a3-55e9fade1aa9" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_4f74a528-c304-499a-99a3-55e9fade1aa9_default" xlink:href="https://xbrl.sec.gov/dei/2020/dei-2020-01-31.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_4f74a528-c304-499a-99a3-55e9fade1aa9" xlink:to="loc_dei_EntityDomain_4f74a528-c304-499a-99a3-55e9fade1aa9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_0038b9e4-6ba9-48c1-99cf-51569f840faf" xlink:href="https://xbrl.sec.gov/dei/2020/dei-2020-01-31.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_4f74a528-c304-499a-99a3-55e9fade1aa9" xlink:to="loc_dei_EntityDomain_0038b9e4-6ba9-48c1-99cf-51569f840faf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_GenOnMember_3f53972f-a097-44e5-b224-6d8ffe7d2b74" xlink:href="nrg-20201231.xsd#nrg_GenOnMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_0038b9e4-6ba9-48c1-99cf-51569f840faf" xlink:to="loc_nrg_GenOnMember_3f53972f-a097-44e5-b224-6d8ffe7d2b74" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_GenOnMidAtlanticMember_7834b476-6e0f-4f43-a38d-937bb7832aa3" xlink:href="nrg-20201231.xsd#nrg_GenOnMidAtlanticMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_0038b9e4-6ba9-48c1-99cf-51569f840faf" xlink:to="loc_nrg_GenOnMidAtlanticMember_7834b476-6e0f-4f43-a38d-937bb7832aa3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringPlanAxis_ddecca30-38ed-4213-a2e0-d8e23def7982" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RestructuringPlanAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_9ff00f35-6984-48e3-a093-23f77066d5e3" xlink:to="loc_us-gaap_RestructuringPlanAxis_ddecca30-38ed-4213-a2e0-d8e23def7982" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringPlanDomain_ddecca30-38ed-4213-a2e0-d8e23def7982_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RestructuringPlanDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RestructuringPlanAxis_ddecca30-38ed-4213-a2e0-d8e23def7982" xlink:to="loc_us-gaap_RestructuringPlanDomain_ddecca30-38ed-4213-a2e0-d8e23def7982_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringPlanDomain_c3db97e2-d320-41a4-a034-595d87e24f67" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RestructuringPlanDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RestructuringPlanAxis_ddecca30-38ed-4213-a2e0-d8e23def7982" xlink:to="loc_us-gaap_RestructuringPlanDomain_c3db97e2-d320-41a4-a034-595d87e24f67" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_RestructuringSupportAgreementMember_07d8c21b-7d6d-4d9e-9e81-f8adf9781128" xlink:href="nrg-20201231.xsd#nrg_RestructuringSupportAgreementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringPlanDomain_c3db97e2-d320-41a4-a034-595d87e24f67" xlink:to="loc_nrg_RestructuringSupportAgreementMember_07d8c21b-7d6d-4d9e-9e81-f8adf9781128" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_0e429862-d737-4088-bc37-3706f0009475" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_9ff00f35-6984-48e3-a093-23f77066d5e3" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_0e429862-d737-4088-bc37-3706f0009475" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_0e429862-d737-4088-bc37-3706f0009475_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_0e429862-d737-4088-bc37-3706f0009475" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_0e429862-d737-4088-bc37-3706f0009475_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_f130dbfe-c228-4af0-9ef9-b309b7c983aa" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_0e429862-d737-4088-bc37-3706f0009475" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_f130dbfe-c228-4af0-9ef9-b309b7c983aa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LetterOfCreditMember_f693322a-38bd-4b55-a4ae-34b37d29bf5d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LetterOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_f130dbfe-c228-4af0-9ef9-b309b7c983aa" xlink:to="loc_us-gaap_LetterOfCreditMember_f693322a-38bd-4b55-a4ae-34b37d29bf5d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_94eb0f1d-b627-44d4-a5a0-cae2cc1ff3f8" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_9ff00f35-6984-48e3-a093-23f77066d5e3" xlink:to="loc_us-gaap_DebtInstrumentAxis_94eb0f1d-b627-44d4-a5a0-cae2cc1ff3f8" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_94eb0f1d-b627-44d4-a5a0-cae2cc1ff3f8_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_94eb0f1d-b627-44d4-a5a0-cae2cc1ff3f8" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_94eb0f1d-b627-44d4-a5a0-cae2cc1ff3f8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_6d41c8de-0654-439b-b13c-6ff9d7b40d50" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_94eb0f1d-b627-44d4-a5a0-cae2cc1ff3f8" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_6d41c8de-0654-439b-b13c-6ff9d7b40d50" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_IntercompanyCreditAgreementMember_c3a50397-bc1f-42d9-8fc9-653efa5b23ad" xlink:href="nrg-20201231.xsd#nrg_IntercompanyCreditAgreementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_6d41c8de-0654-439b-b13c-6ff9d7b40d50" xlink:to="loc_nrg_IntercompanyCreditAgreementMember_c3a50397-bc1f-42d9-8fc9-653efa5b23ad" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/AcquisitionsDiscontinuedOperationsandDispositionsDispositionsDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#AcquisitionsDiscontinuedOperationsandDispositionsDispositionsDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/AcquisitionsDiscontinuedOperationsandDispositionsDispositionsDetails" xlink:type="extended" id="i34209f81c5fd4d70b0787a82c0684cf7_AcquisitionsDiscontinuedOperationsandDispositionsDispositionsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_2cce0086-25b0-4453-886e-a6953f86b2b8" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_PowerGenerationCapacityMegawatts_41549c03-7b1c-49b3-aa6d-4b3e4e48212a" xlink:href="nrg-20201231.xsd#nrg_PowerGenerationCapacityMegawatts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_2cce0086-25b0-4453-886e-a6953f86b2b8" xlink:to="loc_nrg_PowerGenerationCapacityMegawatts_41549c03-7b1c-49b3-aa6d-4b3e4e48212a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromDivestitureOfBusinesses_59c397b2-56f8-417f-81f4-a0109b2d04fe" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ProceedsFromDivestitureOfBusinesses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_2cce0086-25b0-4453-886e-a6953f86b2b8" xlink:to="loc_us-gaap_ProceedsFromDivestitureOfBusinesses_59c397b2-56f8-417f-81f4-a0109b2d04fe" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_PercentageofOwnershipSoldofSubsidiary_51d7828d-629f-4012-9c92-f5a746255573" xlink:href="nrg-20201231.xsd#nrg_PercentageofOwnershipSoldofSubsidiary"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_2cce0086-25b0-4453-886e-a6953f86b2b8" xlink:to="loc_nrg_PercentageofOwnershipSoldofSubsidiary_51d7828d-629f-4012-9c92-f5a746255573" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationConsideration_85ab0931-15cd-4a8a-a8ec-b905640d2e88" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DisposalGroupIncludingDiscontinuedOperationConsideration"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_2cce0086-25b0-4453-886e-a6953f86b2b8" xlink:to="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationConsideration_85ab0931-15cd-4a8a-a8ec-b905640d2e88" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentOtherThanTemporaryImpairment_c3174f4b-7736-409f-959a-fb81dd9e6445" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityMethodInvestmentOtherThanTemporaryImpairment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_2cce0086-25b0-4453-886e-a6953f86b2b8" xlink:to="loc_us-gaap_EquityMethodInvestmentOtherThanTemporaryImpairment_c3174f4b-7736-409f-959a-fb81dd9e6445" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnSaleOfBusiness_6cc5c423-2987-40f4-bb70-1c37a39df18f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GainLossOnSaleOfBusiness"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_2cce0086-25b0-4453-886e-a6953f86b2b8" xlink:to="loc_us-gaap_GainLossOnSaleOfBusiness_6cc5c423-2987-40f4-bb70-1c37a39df18f" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ExtinguishmentOfDebtAmount_2052d3d9-ab29-4373-bb67-b39a33362b4d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ExtinguishmentOfDebtAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_2cce0086-25b0-4453-886e-a6953f86b2b8" xlink:to="loc_us-gaap_ExtinguishmentOfDebtAmount_2052d3d9-ab29-4373-bb67-b39a33362b4d" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainsLossesOnExtinguishmentOfDebt_46fff1c6-852b-41b5-afd3-b679c1f04a26" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GainsLossesOnExtinguishmentOfDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_2cce0086-25b0-4453-886e-a6953f86b2b8" xlink:to="loc_us-gaap_GainsLossesOnExtinguishmentOfDebt_46fff1c6-852b-41b5-afd3-b679c1f04a26" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_ProceedsFromDivestitureOfBusinessesNetOfWorkingCapitalAdjustments_a4eaa72e-49ff-4584-bfb5-29caf1dd4098" xlink:href="nrg-20201231.xsd#nrg_ProceedsFromDivestitureOfBusinessesNetOfWorkingCapitalAdjustments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_2cce0086-25b0-4453-886e-a6953f86b2b8" xlink:to="loc_nrg_ProceedsFromDivestitureOfBusinessesNetOfWorkingCapitalAdjustments_a4eaa72e-49ff-4584-bfb5-29caf1dd4098" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_GuaranteeObligationsEstimatedExposure_e75ac021-68e2-4883-bb1e-25cf0757a3cb" xlink:href="nrg-20201231.xsd#nrg_GuaranteeObligationsEstimatedExposure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_2cce0086-25b0-4453-886e-a6953f86b2b8" xlink:to="loc_nrg_GuaranteeObligationsEstimatedExposure_e75ac021-68e2-4883-bb1e-25cf0757a3cb" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_CashCollateral_1e767ebe-bf32-4317-9a12-971e7be08909" xlink:href="nrg-20201231.xsd#nrg_CashCollateral"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_2cce0086-25b0-4453-886e-a6953f86b2b8" xlink:to="loc_nrg_CashCollateral_1e767ebe-bf32-4317-9a12-971e7be08909" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromIssuanceOfDebt_5e8cca3d-888a-4239-be05-004e7a67370a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ProceedsFromIssuanceOfDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_2cce0086-25b0-4453-886e-a6953f86b2b8" xlink:to="loc_us-gaap_ProceedsFromIssuanceOfDebt_5e8cca3d-888a-4239-be05-004e7a67370a" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromContributionsFromAffiliates_50979b5e-a299-4ff1-99d3-1af8e7c75cd1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ProceedsFromContributionsFromAffiliates"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_2cce0086-25b0-4453-886e-a6953f86b2b8" xlink:to="loc_us-gaap_ProceedsFromContributionsFromAffiliates_50979b5e-a299-4ff1-99d3-1af8e7c75cd1" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_9ef4a0a0-40c5-4099-98c9-68ffa98206bc" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_2cce0086-25b0-4453-886e-a6953f86b2b8" xlink:to="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_9ef4a0a0-40c5-4099-98c9-68ffa98206bc" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_284ccca6-49de-447d-8bf8-e437d4820c05" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_9ef4a0a0-40c5-4099-98c9-68ffa98206bc" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_284ccca6-49de-447d-8bf8-e437d4820c05" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_284ccca6-49de-447d-8bf8-e437d4820c05_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_284ccca6-49de-447d-8bf8-e437d4820c05" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_284ccca6-49de-447d-8bf8-e437d4820c05_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_6f76a42d-4700-4621-9fe9-2242423f960a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_284ccca6-49de-447d-8bf8-e437d4820c05" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_6f76a42d-4700-4621-9fe9-2242423f960a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_281b7413-4121-4527-ab37-dfeb4fef9579" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_6f76a42d-4700-4621-9fe9-2242423f960a" xlink:to="loc_us-gaap_SubsequentEventMember_281b7413-4121-4527-ab37-dfeb4fef9579" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementScenarioAxis_0c33e1fe-6893-454e-a140-f583f8f3f678" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_StatementScenarioAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_9ef4a0a0-40c5-4099-98c9-68ffa98206bc" xlink:to="loc_srt_StatementScenarioAxis_0c33e1fe-6893-454e-a140-f583f8f3f678" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_0c33e1fe-6893-454e-a140-f583f8f3f678_default" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ScenarioUnspecifiedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementScenarioAxis_0c33e1fe-6893-454e-a140-f583f8f3f678" xlink:to="loc_srt_ScenarioUnspecifiedDomain_0c33e1fe-6893-454e-a140-f583f8f3f678_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_85164532-ead9-4fe6-ac96-d440005f7ce0" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ScenarioUnspecifiedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementScenarioAxis_0c33e1fe-6893-454e-a140-f583f8f3f678" xlink:to="loc_srt_ScenarioUnspecifiedDomain_85164532-ead9-4fe6-ac96-d440005f7ce0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioForecastMember_1b9342c2-3aac-47e2-b040-465343cbfe21" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ScenarioForecastMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ScenarioUnspecifiedDomain_85164532-ead9-4fe6-ac96-d440005f7ce0" xlink:to="loc_srt_ScenarioForecastMember_1b9342c2-3aac-47e2-b040-465343cbfe21" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_dd698e64-4435-409d-a08d-0c05fdf1f87c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_9ef4a0a0-40c5-4099-98c9-68ffa98206bc" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_dd698e64-4435-409d-a08d-0c05fdf1f87c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_dd698e64-4435-409d-a08d-0c05fdf1f87c_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_dd698e64-4435-409d-a08d-0c05fdf1f87c" xlink:to="loc_us-gaap_SegmentDomain_dd698e64-4435-409d-a08d-0c05fdf1f87c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_76892e79-13cb-4112-96f9-3425327d50ac" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_dd698e64-4435-409d-a08d-0c05fdf1f87c" xlink:to="loc_us-gaap_SegmentDomain_76892e79-13cb-4112-96f9-3425327d50ac" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_EastAndWestMember_1b238705-41fc-4f6f-9ef5-5d16daac6a62" xlink:href="nrg-20201231.xsd#nrg_EastAndWestMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_76892e79-13cb-4112-96f9-3425327d50ac" xlink:to="loc_nrg_EastAndWestMember_1b238705-41fc-4f6f-9ef5-5d16daac6a62" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_91ffae5a-a22e-4117-b9cb-0931272d8456" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_9ef4a0a0-40c5-4099-98c9-68ffa98206bc" xlink:to="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_91ffae5a-a22e-4117-b9cb-0931272d8456" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_91ffae5a-a22e-4117-b9cb-0931272d8456_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_91ffae5a-a22e-4117-b9cb-0931272d8456" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_91ffae5a-a22e-4117-b9cb-0931272d8456_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_9ff185ac-d4a4-452b-9f2f-e5b40490da78" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_91ffae5a-a22e-4117-b9cb-0931272d8456" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_9ff185ac-d4a4-452b-9f2f-e5b40490da78" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_AguaCalienteSolarProjectMember_85ce6ef8-8b42-48bd-804f-7f22ecd52cfb" xlink:href="nrg-20201231.xsd#nrg_AguaCalienteSolarProjectMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_9ff185ac-d4a4-452b-9f2f-e5b40490da78" xlink:to="loc_nrg_AguaCalienteSolarProjectMember_85ce6ef8-8b42-48bd-804f-7f22ecd52cfb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_HomeSolarMember_dcc6abe4-94ee-465c-a27e-3deb1970aa9d" xlink:href="nrg-20201231.xsd#nrg_HomeSolarMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_9ff185ac-d4a4-452b-9f2f-e5b40490da78" xlink:to="loc_nrg_HomeSolarMember_dcc6abe4-94ee-465c-a27e-3deb1970aa9d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_BETMMember_914846bc-0d80-4704-b8fe-0c2d7dd74b25" xlink:href="nrg-20201231.xsd#nrg_BETMMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_9ff185ac-d4a4-452b-9f2f-e5b40490da78" xlink:to="loc_nrg_BETMMember_914846bc-0d80-4704-b8fe-0c2d7dd74b25" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_CanalThreeMember_e49ec53d-7f31-48a4-b427-68d0a85dd5ee" xlink:href="nrg-20201231.xsd#nrg_CanalThreeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_9ff185ac-d4a4-452b-9f2f-e5b40490da78" xlink:to="loc_nrg_CanalThreeMember_e49ec53d-7f31-48a4-b427-68d0a85dd5ee" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_OtherMember_7be7c87c-1876-4b55-9a0f-881d63b3defc" xlink:href="nrg-20201231.xsd#nrg_OtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_9ff185ac-d4a4-452b-9f2f-e5b40490da78" xlink:to="loc_nrg_OtherMember_7be7c87c-1876-4b55-9a0f-881d63b3defc" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationAxis_7e759b46-7d5e-41ad-b1b8-a3dadb580286" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DisposalGroupClassificationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_9ef4a0a0-40c5-4099-98c9-68ffa98206bc" xlink:to="loc_us-gaap_DisposalGroupClassificationAxis_7e759b46-7d5e-41ad-b1b8-a3dadb580286" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationDomain_7e759b46-7d5e-41ad-b1b8-a3dadb580286_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DisposalGroupClassificationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DisposalGroupClassificationAxis_7e759b46-7d5e-41ad-b1b8-a3dadb580286" xlink:to="loc_us-gaap_DisposalGroupClassificationDomain_7e759b46-7d5e-41ad-b1b8-a3dadb580286_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationDomain_42c392ff-c7d0-4971-90f2-82c1474cd166" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DisposalGroupClassificationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DisposalGroupClassificationAxis_7e759b46-7d5e-41ad-b1b8-a3dadb580286" xlink:to="loc_us-gaap_DisposalGroupClassificationDomain_42c392ff-c7d0-4971-90f2-82c1474cd166" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupHeldForSaleOrDisposedOfBySaleNotDiscontinuedOperationsMember_781b5c67-eeb2-44ea-af26-5aa3890092fc" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DisposalGroupHeldForSaleOrDisposedOfBySaleNotDiscontinuedOperationsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupClassificationDomain_42c392ff-c7d0-4971-90f2-82c1474cd166" xlink:to="loc_us-gaap_DisposalGroupHeldForSaleOrDisposedOfBySaleNotDiscontinuedOperationsMember_781b5c67-eeb2-44ea-af26-5aa3890092fc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GuaranteeObligationsByNatureAxis_84c4ba04-2ed5-458b-8ba8-3eee99c69a98" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GuaranteeObligationsByNatureAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_9ef4a0a0-40c5-4099-98c9-68ffa98206bc" xlink:to="loc_us-gaap_GuaranteeObligationsByNatureAxis_84c4ba04-2ed5-458b-8ba8-3eee99c69a98" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GuaranteeObligationsNatureDomain_84c4ba04-2ed5-458b-8ba8-3eee99c69a98_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GuaranteeObligationsNatureDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_GuaranteeObligationsByNatureAxis_84c4ba04-2ed5-458b-8ba8-3eee99c69a98" xlink:to="loc_us-gaap_GuaranteeObligationsNatureDomain_84c4ba04-2ed5-458b-8ba8-3eee99c69a98_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GuaranteeObligationsNatureDomain_0c506980-538a-4d29-bb89-7d132845a236" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GuaranteeObligationsNatureDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_GuaranteeObligationsByNatureAxis_84c4ba04-2ed5-458b-8ba8-3eee99c69a98" xlink:to="loc_us-gaap_GuaranteeObligationsNatureDomain_0c506980-538a-4d29-bb89-7d132845a236" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LetterOfCreditMember_4052e3eb-d538-4bd0-9145-b5669efca237" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LetterOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GuaranteeObligationsNatureDomain_0c506980-538a-4d29-bb89-7d132845a236" xlink:to="loc_us-gaap_LetterOfCreditMember_4052e3eb-d538-4bd0-9145-b5669efca237" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GuaranteeTypeOtherMember_75b59c0f-086e-404f-a141-b5cddec96e07" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GuaranteeTypeOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GuaranteeObligationsNatureDomain_0c506980-538a-4d29-bb89-7d132845a236" xlink:to="loc_us-gaap_GuaranteeTypeOtherMember_75b59c0f-086e-404f-a141-b5cddec96e07" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_e58280be-b815-421a-8380-dbe4ba79f13f" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_9ef4a0a0-40c5-4099-98c9-68ffa98206bc" xlink:to="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_e58280be-b815-421a-8380-dbe4ba79f13f" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_e58280be-b815-421a-8380-dbe4ba79f13f_default" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_e58280be-b815-421a-8380-dbe4ba79f13f" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_e58280be-b815-421a-8380-dbe4ba79f13f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_12036646-7c8d-4bad-9c8d-970a64e9bd5a" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_e58280be-b815-421a-8380-dbe4ba79f13f" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_12036646-7c8d-4bad-9c8d-970a64e9bd5a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_ArthurKillPlantMember_7bf3587d-b496-4a9e-8dbf-ad25b0a5571c" xlink:href="nrg-20201231.xsd#nrg_ArthurKillPlantMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_12036646-7c8d-4bad-9c8d-970a64e9bd5a" xlink:to="loc_nrg_ArthurKillPlantMember_7bf3587d-b496-4a9e-8dbf-ad25b0a5571c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_HomeSolarMember_9c6e81e7-50c1-4c97-8382-13f9be3f296e" xlink:href="nrg-20201231.xsd#nrg_HomeSolarMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_12036646-7c8d-4bad-9c8d-970a64e9bd5a" xlink:to="loc_nrg_HomeSolarMember_9c6e81e7-50c1-4c97-8382-13f9be3f296e" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/FairValueofFinancialInstruments" xlink:type="simple" xlink:href="nrg-20201231.xsd#FairValueofFinancialInstruments"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/FairValueofFinancialInstruments" xlink:type="extended" id="ia5f04dabb3844fa5aad2b1153d8d4dba_FairValueofFinancialInstruments"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/FairValueofFinancialInstrumentsTables" xlink:type="simple" xlink:href="nrg-20201231.xsd#FairValueofFinancialInstrumentsTables"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/FairValueofFinancialInstrumentsTables" xlink:type="extended" id="i7802a0bc510d493ab02c15e49023d9ce_FairValueofFinancialInstrumentsTables"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/FairValueofFinancialInstrumentsEstimatedCarryingAmountsofFairValueofFinancialInstrumentsnotCarriedatFairValueDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#FairValueofFinancialInstrumentsEstimatedCarryingAmountsofFairValueofFinancialInstrumentsnotCarriedatFairValueDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/FairValueofFinancialInstrumentsEstimatedCarryingAmountsofFairValueofFinancialInstrumentsnotCarriedatFairValueDetails" xlink:type="extended" id="i73038101a01743ec81d4285fc08ace2a_FairValueofFinancialInstrumentsEstimatedCarryingAmountsofFairValueofFinancialInstrumentsnotCarriedatFairValueDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_486b2dee-735c-4e2b-a71d-40c5e77c6119" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentsFinancialAssetsBalanceSheetGroupingsAbstract_5108753f-6bbd-407a-9b5a-b6ca8413da2e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FinancialInstrumentsFinancialAssetsBalanceSheetGroupingsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_486b2dee-735c-4e2b-a71d-40c5e77c6119" xlink:to="loc_us-gaap_FinancialInstrumentsFinancialAssetsBalanceSheetGroupingsAbstract_5108753f-6bbd-407a-9b5a-b6ca8413da2e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NotesReceivableGross_31762914-80bf-425d-a37f-1afa1df0b2fa" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NotesReceivableGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancialInstrumentsFinancialAssetsBalanceSheetGroupingsAbstract_5108753f-6bbd-407a-9b5a-b6ca8413da2e" xlink:to="loc_us-gaap_NotesReceivableGross_31762914-80bf-425d-a37f-1afa1df0b2fa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentsFinancialLiabilitiesBalanceSheetGroupingsAbstract_222b4077-b0f0-4746-a3f7-ed2c7f3385e2" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FinancialInstrumentsFinancialLiabilitiesBalanceSheetGroupingsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_486b2dee-735c-4e2b-a71d-40c5e77c6119" xlink:to="loc_us-gaap_FinancialInstrumentsFinancialLiabilitiesBalanceSheetGroupingsAbstract_222b4077-b0f0-4746-a3f7-ed2c7f3385e2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_a2916fbc-428e-4398-b555-95a7f8616ee9" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancialInstrumentsFinancialLiabilitiesBalanceSheetGroupingsAbstract_222b4077-b0f0-4746-a3f7-ed2c7f3385e2" xlink:to="loc_us-gaap_LongTermDebt_a2916fbc-428e-4398-b555-95a7f8616ee9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtLongtermAndShorttermCombinedAmountAbstract_e17c23ee-def0-4434-8563-5559f02619c8" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtLongtermAndShorttermCombinedAmountAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_486b2dee-735c-4e2b-a71d-40c5e77c6119" xlink:to="loc_us-gaap_DebtLongtermAndShorttermCombinedAmountAbstract_e17c23ee-def0-4434-8563-5559f02619c8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFairValue_4d628f20-a27a-4ceb-90a9-299a576d9622" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtLongtermAndShorttermCombinedAmountAbstract_e17c23ee-def0-4434-8563-5559f02619c8" xlink:to="loc_us-gaap_DebtInstrumentFairValue_4d628f20-a27a-4ceb-90a9-299a576d9622" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByBalanceSheetGroupingTable_690d64b8-c387-4004-aa02-ebf195a12626" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueByBalanceSheetGroupingTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_486b2dee-735c-4e2b-a71d-40c5e77c6119" xlink:to="loc_us-gaap_FairValueByBalanceSheetGroupingTable_690d64b8-c387-4004-aa02-ebf195a12626" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByMeasurementBasisAxis_d4a519dd-dbc7-4893-975e-375b8b40c671" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueByMeasurementBasisAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueByBalanceSheetGroupingTable_690d64b8-c387-4004-aa02-ebf195a12626" xlink:to="loc_us-gaap_FairValueByMeasurementBasisAxis_d4a519dd-dbc7-4893-975e-375b8b40c671" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_d4a519dd-dbc7-4893-975e-375b8b40c671_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PortionAtFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementBasisAxis_d4a519dd-dbc7-4893-975e-375b8b40c671" xlink:to="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_d4a519dd-dbc7-4893-975e-375b8b40c671_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueDisclosureItemAmountsDomain_0678eca6-7318-484e-a702-37d711aeaf4d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueDisclosureItemAmountsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementBasisAxis_d4a519dd-dbc7-4893-975e-375b8b40c671" xlink:to="loc_us-gaap_FairValueDisclosureItemAmountsDomain_0678eca6-7318-484e-a702-37d711aeaf4d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_a27d135c-0b2f-4e73-b222-bbdebfb9545f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PortionAtFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueDisclosureItemAmountsDomain_0678eca6-7318-484e-a702-37d711aeaf4d" xlink:to="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_a27d135c-0b2f-4e73-b222-bbdebfb9545f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CarryingReportedAmountFairValueDisclosureMember_91b63a71-98e5-4c97-b8fe-a4c9cc1d0664" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CarryingReportedAmountFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueDisclosureItemAmountsDomain_0678eca6-7318-484e-a702-37d711aeaf4d" xlink:to="loc_us-gaap_CarryingReportedAmountFairValueDisclosureMember_91b63a71-98e5-4c97-b8fe-a4c9cc1d0664" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EstimateOfFairValueFairValueDisclosureMember_94e872a4-33a9-4ba4-9e53-66d39c4676e6" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EstimateOfFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueDisclosureItemAmountsDomain_0678eca6-7318-484e-a702-37d711aeaf4d" xlink:to="loc_us-gaap_EstimateOfFairValueFairValueDisclosureMember_94e872a4-33a9-4ba4-9e53-66d39c4676e6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_c272b766-a9de-4c82-aec9-71c75c880a8a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueByBalanceSheetGroupingTable_690d64b8-c387-4004-aa02-ebf195a12626" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_c272b766-a9de-4c82-aec9-71c75c880a8a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_c272b766-a9de-4c82-aec9-71c75c880a8a_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_c272b766-a9de-4c82-aec9-71c75c880a8a" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_c272b766-a9de-4c82-aec9-71c75c880a8a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_0fd323d4-fd94-4ba5-b6bc-2fd33554429d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_c272b766-a9de-4c82-aec9-71c75c880a8a" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_0fd323d4-fd94-4ba5-b6bc-2fd33554429d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_517b3937-0e72-4542-a061-4a71c477de5a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_0fd323d4-fd94-4ba5-b6bc-2fd33554429d" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_517b3937-0e72-4542-a061-4a71c477de5a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_59336c58-b783-45bc-b92b-324bc665ea19" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_0fd323d4-fd94-4ba5-b6bc-2fd33554429d" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_59336c58-b783-45bc-b92b-324bc665ea19" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/FairValueofFinancialInstrumentsAssetsandLiabilitiesMeasuredandRecordedatFairValueDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#FairValueofFinancialInstrumentsAssetsandLiabilitiesMeasuredandRecordedatFairValueDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/FairValueofFinancialInstrumentsAssetsandLiabilitiesMeasuredandRecordedatFairValueDetails" xlink:type="extended" id="i00287a09126942a19e6c8b11199663da_FairValueofFinancialInstrumentsAssetsandLiabilitiesMeasuredandRecordedatFairValueDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_8a7e48a6-f26c-4a4d-9a72-a9ab69e0408c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_286e04c1-958e-4be2-ba8c-9a0f55cec91f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_8a7e48a6-f26c-4a4d-9a72-a9ab69e0408c" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_286e04c1-958e-4be2-ba8c-9a0f55cec91f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_NuclearTrustFundInvestmentsAbstract_37199c20-cc35-42f3-b64e-8884b8c10ef5" xlink:href="nrg-20201231.xsd#nrg_NuclearTrustFundInvestmentsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_8a7e48a6-f26c-4a4d-9a72-a9ab69e0408c" xlink:to="loc_nrg_NuclearTrustFundInvestmentsAbstract_37199c20-cc35-42f3-b64e-8884b8c10ef5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DecommissioningFundInvestments_8b944fda-3021-4f4e-a599-5aff9d1c703c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DecommissioningFundInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_NuclearTrustFundInvestmentsAbstract_37199c20-cc35-42f3-b64e-8884b8c10ef5" xlink:to="loc_us-gaap_DecommissioningFundInvestments_8b944fda-3021-4f4e-a599-5aff9d1c703c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentsOwnedAtFairValueByTypeAbstract_223bfe37-4feb-4cc3-aeeb-e49fcabeba47" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FinancialInstrumentsOwnedAtFairValueByTypeAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_8a7e48a6-f26c-4a4d-9a72-a9ab69e0408c" xlink:to="loc_us-gaap_FinancialInstrumentsOwnedAtFairValueByTypeAbstract_223bfe37-4feb-4cc3-aeeb-e49fcabeba47" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentsOwnedUSGovernmentAndAgencyObligationsAtFairValue_fdb5bd03-40cf-4f8b-830f-b138c17917c9" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FinancialInstrumentsOwnedUSGovernmentAndAgencyObligationsAtFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancialInstrumentsOwnedAtFairValueByTypeAbstract_223bfe37-4feb-4cc3-aeeb-e49fcabeba47" xlink:to="loc_us-gaap_FinancialInstrumentsOwnedUSGovernmentAndAgencyObligationsAtFairValue_fdb5bd03-40cf-4f8b-830f-b138c17917c9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssetsAbstract_ed68dd5f-55e5-420b-ac63-7566d4dabaec" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeAssetsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_8a7e48a6-f26c-4a4d-9a72-a9ab69e0408c" xlink:to="loc_us-gaap_DerivativeAssetsAbstract_ed68dd5f-55e5-420b-ac63-7566d4dabaec" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFairValueOfDerivativeAsset_38573398-430e-45c9-ad23-44ad70e389d7" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeFairValueOfDerivativeAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeAssetsAbstract_ed68dd5f-55e5-420b-ac63-7566d4dabaec" xlink:to="loc_us-gaap_DerivativeFairValueOfDerivativeAsset_38573398-430e-45c9-ad23-44ad70e389d7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_MeasuredUsingNetAssetValuePracticalExpedientAbstract_60e63326-0560-4058-999e-2860524e0358" xlink:href="nrg-20201231.xsd#nrg_MeasuredUsingNetAssetValuePracticalExpedientAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_8a7e48a6-f26c-4a4d-9a72-a9ab69e0408c" xlink:to="loc_nrg_MeasuredUsingNetAssetValuePracticalExpedientAbstract_60e63326-0560-4058-999e-2860524e0358" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentsFairValueDisclosure_f7e0306e-90f2-47a3-aa7c-e9ccb077b95e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InvestmentsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_MeasuredUsingNetAssetValuePracticalExpedientAbstract_60e63326-0560-4058-999e-2860524e0358" xlink:to="loc_us-gaap_InvestmentsFairValueDisclosure_f7e0306e-90f2-47a3-aa7c-e9ccb077b95e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsFairValueDisclosure_672252b5-84e4-4fac-b82e-56a1990c0ffe" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AssetsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_8a7e48a6-f26c-4a4d-9a72-a9ab69e0408c" xlink:to="loc_us-gaap_AssetsFairValueDisclosure_672252b5-84e4-4fac-b82e-56a1990c0ffe" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilityFairValueNetAbstract_f2036e66-29c6-4658-8961-d7cd71755c08" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeLiabilityFairValueNetAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_8a7e48a6-f26c-4a4d-9a72-a9ab69e0408c" xlink:to="loc_us-gaap_DerivativeLiabilityFairValueNetAbstract_f2036e66-29c6-4658-8961-d7cd71755c08" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFairValueOfDerivativeLiability_c3ba9a52-f989-4a68-9ee0-345471c92213" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeFairValueOfDerivativeLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLiabilityFairValueNetAbstract_f2036e66-29c6-4658-8961-d7cd71755c08" xlink:to="loc_us-gaap_DerivativeFairValueOfDerivativeLiability_c3ba9a52-f989-4a68-9ee0-345471c92213" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesFairValueDisclosure_0dc70aef-750d-47de-a7fc-09ba031924d5" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LiabilitiesFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_8a7e48a6-f26c-4a4d-9a72-a9ab69e0408c" xlink:to="loc_us-gaap_LiabilitiesFairValueDisclosure_0dc70aef-750d-47de-a7fc-09ba031924d5" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_4ba4af35-c8bf-43d6-b925-f02aa292ebe2" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_8a7e48a6-f26c-4a4d-9a72-a9ab69e0408c" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_4ba4af35-c8bf-43d6-b925-f02aa292ebe2" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_25412049-0dfe-439f-83d0-c98a88eede90" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_4ba4af35-c8bf-43d6-b925-f02aa292ebe2" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_25412049-0dfe-439f-83d0-c98a88eede90" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_25412049-0dfe-439f-83d0-c98a88eede90_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_25412049-0dfe-439f-83d0-c98a88eede90" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_25412049-0dfe-439f-83d0-c98a88eede90_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_4d4f2bae-a2f4-4727-baab-5b9f11f99b86" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_25412049-0dfe-439f-83d0-c98a88eede90" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_4d4f2bae-a2f4-4727-baab-5b9f11f99b86" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_d9077f1b-264b-4ce0-b724-3d0631a724c3" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueInputsLevel1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_4d4f2bae-a2f4-4727-baab-5b9f11f99b86" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_d9077f1b-264b-4ce0-b724-3d0631a724c3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_877bc773-1ae6-4f79-af70-65b9ce1dfd7c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_4d4f2bae-a2f4-4727-baab-5b9f11f99b86" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_877bc773-1ae6-4f79-af70-65b9ce1dfd7c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_7bddcd31-4cd5-4f22-b956-64170fbb37ce" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_4d4f2bae-a2f4-4727-baab-5b9f11f99b86" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_7bddcd31-4cd5-4f22-b956-64170fbb37ce" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_fbf156bc-4b8c-4bbd-a457-780d3e6cde77" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_4ba4af35-c8bf-43d6-b925-f02aa292ebe2" xlink:to="loc_us-gaap_FinancialInstrumentAxis_fbf156bc-4b8c-4bbd-a457-780d3e6cde77" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_fbf156bc-4b8c-4bbd-a457-780d3e6cde77_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_fbf156bc-4b8c-4bbd-a457-780d3e6cde77" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_fbf156bc-4b8c-4bbd-a457-780d3e6cde77_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_3945bef0-33f5-47db-bbae-fb3be080aa28" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_fbf156bc-4b8c-4bbd-a457-780d3e6cde77" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_3945bef0-33f5-47db-bbae-fb3be080aa28" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsMember_df999bf1-8e42-4e58-8803-42a6188bdc21" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CashAndCashEquivalentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_3945bef0-33f5-47db-bbae-fb3be080aa28" xlink:to="loc_us-gaap_CashAndCashEquivalentsMember_df999bf1-8e42-4e58-8803-42a6188bdc21" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember_04bf636c-3d69-4faa-a70b-ee49bd7f4c88" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_3945bef0-33f5-47db-bbae-fb3be080aa28" xlink:to="loc_us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember_04bf636c-3d69-4faa-a70b-ee49bd7f4c88" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember_64d48484-f2fd-4e5a-b07a-f7fa7ce7f0ff" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_3945bef0-33f5-47db-bbae-fb3be080aa28" xlink:to="loc_us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember_64d48484-f2fd-4e5a-b07a-f7fa7ce7f0ff" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialMortgageBackedSecuritiesMember_79db65cc-4786-42a5-847e-6ceb82623449" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommercialMortgageBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_3945bef0-33f5-47db-bbae-fb3be080aa28" xlink:to="loc_us-gaap_CommercialMortgageBackedSecuritiesMember_79db65cc-4786-42a5-847e-6ceb82623449" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateDebtSecuritiesMember_a585e92e-f944-42bf-b4e7-93e6adbb14b1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CorporateDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_3945bef0-33f5-47db-bbae-fb3be080aa28" xlink:to="loc_us-gaap_CorporateDebtSecuritiesMember_a585e92e-f944-42bf-b4e7-93e6adbb14b1" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesMember_69c4972a-ca58-4881-b109-c20250f8e413" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquitySecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_3945bef0-33f5-47db-bbae-fb3be080aa28" xlink:to="loc_us-gaap_EquitySecuritiesMember_69c4972a-ca58-4881-b109-c20250f8e413" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignGovernmentDebtSecuritiesMember_bed2622e-a210-4af9-bfa9-35f1e9c3bcaa" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ForeignGovernmentDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_3945bef0-33f5-47db-bbae-fb3be080aa28" xlink:to="loc_us-gaap_ForeignGovernmentDebtSecuritiesMember_bed2622e-a210-4af9-bfa9-35f1e9c3bcaa" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_EquitySecuritiesNuclearTrustFundMember_06659f07-6422-40a8-aa3e-359aee516359" xlink:href="nrg-20201231.xsd#nrg_EquitySecuritiesNuclearTrustFundMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_3945bef0-33f5-47db-bbae-fb3be080aa28" xlink:to="loc_nrg_EquitySecuritiesNuclearTrustFundMember_06659f07-6422-40a8-aa3e-359aee516359" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_5da58005-e371-4d9e-b99e-92bd829a440a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_4ba4af35-c8bf-43d6-b925-f02aa292ebe2" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_5da58005-e371-4d9e-b99e-92bd829a440a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_5da58005-e371-4d9e-b99e-92bd829a440a_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_5da58005-e371-4d9e-b99e-92bd829a440a" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_5da58005-e371-4d9e-b99e-92bd829a440a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_f48e3c9a-4e2d-4455-b79a-fbc5c714fb1e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_5da58005-e371-4d9e-b99e-92bd829a440a" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_f48e3c9a-4e2d-4455-b79a-fbc5c714fb1e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommodityContractMember_3777c627-b13c-47a6-b51a-ede16184b878" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommodityContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_f48e3c9a-4e2d-4455-b79a-fbc5c714fb1e" xlink:to="loc_us-gaap_CommodityContractMember_3777c627-b13c-47a6-b51a-ede16184b878" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/FairValueofFinancialInstrumentsReconciliationofLevel3FinancialInstrumentsDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#FairValueofFinancialInstrumentsReconciliationofLevel3FinancialInstrumentsDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/FairValueofFinancialInstrumentsReconciliationofLevel3FinancialInstrumentsDetails" xlink:type="extended" id="i94c7f425544d461b92f9d829cb647f84_FairValueofFinancialInstrumentsReconciliationofLevel3FinancialInstrumentsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasuredOnRecurringBasisGainLossIncludedInEarningsAbstract_c4d7b404-12da-47b1-aad3-8ccda07fc071" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueMeasuredOnRecurringBasisGainLossIncludedInEarningsAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_40256140-2f2d-4606-85ec-f422b307f8ae" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasuredOnRecurringBasisGainLossIncludedInEarningsAbstract_c4d7b404-12da-47b1-aad3-8ccda07fc071" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_40256140-2f2d-4606-85ec-f422b307f8ae" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisWithUnobservableInputs_30c6cf08-2c25-4c49-85eb-307ff604a826" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisWithUnobservableInputs"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_40256140-2f2d-4606-85ec-f422b307f8ae" xlink:to="loc_us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisWithUnobservableInputs_30c6cf08-2c25-4c49-85eb-307ff604a826" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputsReconciliationAcquisition_8d72f114-984b-4626-b8c1-b57d218acbfe" xlink:href="nrg-20201231.xsd#nrg_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputsReconciliationAcquisition"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_40256140-2f2d-4606-85ec-f422b307f8ae" xlink:to="loc_nrg_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputsReconciliationAcquisition_8d72f114-984b-4626-b8c1-b57d218acbfe" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetAndLiabilityRealizedAndUnrealizedGainLossAbstract_16a2e6f7-5104-46f9-a081-c0ee94d07f4e" xlink:href="nrg-20201231.xsd#nrg_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetAndLiabilityRealizedAndUnrealizedGainLossAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_40256140-2f2d-4606-85ec-f422b307f8ae" xlink:to="loc_nrg_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetAndLiabilityRealizedAndUnrealizedGainLossAbstract_16a2e6f7-5104-46f9-a081-c0ee94d07f4e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputsReconciliationGainLossIncludedInEarnings_23511b33-88b6-4cbe-b9b1-3aba46c25350" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputsReconciliationGainLossIncludedInEarnings"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetAndLiabilityRealizedAndUnrealizedGainLossAbstract_16a2e6f7-5104-46f9-a081-c0ee94d07f4e" xlink:to="loc_us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputsReconciliationGainLossIncludedInEarnings_23511b33-88b6-4cbe-b9b1-3aba46c25350" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputsReconciliationPurchases_2c1c749f-422e-40f6-8e81-5ea0811d0005" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputsReconciliationPurchases"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_40256140-2f2d-4606-85ec-f422b307f8ae" xlink:to="loc_us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputsReconciliationPurchases_2c1c749f-422e-40f6-8e81-5ea0811d0005" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputsReconciliationSales_10ddb16a-db3d-4cb8-b52e-830a2c4ebbac" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputsReconciliationSales"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_40256140-2f2d-4606-85ec-f422b307f8ae" xlink:to="loc_us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputsReconciliationSales_10ddb16a-db3d-4cb8-b52e-830a2c4ebbac" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputsReconciliationTransfersIntoLevel3_f4dec544-aece-44f3-abf4-15fd612fb9f1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputsReconciliationTransfersIntoLevel3"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_40256140-2f2d-4606-85ec-f422b307f8ae" xlink:to="loc_us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputsReconciliationTransfersIntoLevel3_f4dec544-aece-44f3-abf4-15fd612fb9f1" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputsReconciliationTransfersOutOfLevel3_7658f7dd-d33e-42f8-82bc-168a468462a8" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputsReconciliationTransfersOutOfLevel3"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_40256140-2f2d-4606-85ec-f422b307f8ae" xlink:to="loc_us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputsReconciliationTransfersOutOfLevel3_7658f7dd-d33e-42f8-82bc-168a468462a8" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisWithUnobservableInputs_f847d1e3-08b5-4492-8f3f-7758e66a1c8d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisWithUnobservableInputs"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisChangeInUnrealizedGainLoss_d6e04d63-2ec6-4fdc-9a4f-3d4068466309" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisChangeInUnrealizedGainLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_40256140-2f2d-4606-85ec-f422b307f8ae" xlink:to="loc_us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisChangeInUnrealizedGainLoss_d6e04d63-2ec6-4fdc-9a4f-3d4068466309" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasuredOnRecurringBasisGainLossIncludedInEarningsTable_ecef54a9-0c62-40dc-92fa-5308a048d0f8" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueMeasuredOnRecurringBasisGainLossIncludedInEarningsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueMeasuredOnRecurringBasisGainLossIncludedInEarningsAbstract_c4d7b404-12da-47b1-aad3-8ccda07fc071" xlink:to="loc_us-gaap_FairValueMeasuredOnRecurringBasisGainLossIncludedInEarningsTable_ecef54a9-0c62-40dc-92fa-5308a048d0f8" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_c4c505a1-3017-45dc-b702-0170c37fa877" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueMeasuredOnRecurringBasisGainLossIncludedInEarningsTable_ecef54a9-0c62-40dc-92fa-5308a048d0f8" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_c4c505a1-3017-45dc-b702-0170c37fa877" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_c4c505a1-3017-45dc-b702-0170c37fa877_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_c4c505a1-3017-45dc-b702-0170c37fa877" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_c4c505a1-3017-45dc-b702-0170c37fa877_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_3f7f353f-e901-4f19-a176-b63302d9a8fd" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_c4c505a1-3017-45dc-b702-0170c37fa877" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_3f7f353f-e901-4f19-a176-b63302d9a8fd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_9409a958-1780-4f2b-940b-134ba7f5d5c6" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_3f7f353f-e901-4f19-a176-b63302d9a8fd" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_9409a958-1780-4f2b-940b-134ba7f5d5c6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_78df51c1-a195-4f89-af22-c54d7b672f08" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueMeasuredOnRecurringBasisGainLossIncludedInEarningsTable_ecef54a9-0c62-40dc-92fa-5308a048d0f8" xlink:to="loc_us-gaap_FinancialInstrumentAxis_78df51c1-a195-4f89-af22-c54d7b672f08" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_78df51c1-a195-4f89-af22-c54d7b672f08_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_78df51c1-a195-4f89-af22-c54d7b672f08" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_78df51c1-a195-4f89-af22-c54d7b672f08_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_3ce860dd-0a5f-4bb7-ae8f-6f189815cbd9" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_78df51c1-a195-4f89-af22-c54d7b672f08" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_3ce860dd-0a5f-4bb7-ae8f-6f189815cbd9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesMember_241223c7-ed2e-4a26-a7e1-cb66274d9e31" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_3ce860dd-0a5f-4bb7-ae8f-6f189815cbd9" xlink:to="loc_us-gaap_DebtSecuritiesMember_241223c7-ed2e-4a26-a7e1-cb66274d9e31" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeMember_8a409b39-72c8-4fc5-940e-0dfbbbf703b1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_3ce860dd-0a5f-4bb7-ae8f-6f189815cbd9" xlink:to="loc_us-gaap_DerivativeMember_8a409b39-72c8-4fc5-940e-0dfbbbf703b1" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/FairValueofFinancialInstrumentsDerivativeFairValueMeasurementsNarrativeDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#FairValueofFinancialInstrumentsDerivativeFairValueMeasurementsNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/FairValueofFinancialInstrumentsDerivativeFairValueMeasurementsNarrativeDetails" xlink:type="extended" id="ibceb77642d3747169168e67680351fdc_FairValueofFinancialInstrumentsDerivativeFairValueMeasurementsNarrativeDetails"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/FairValueofFinancialInstrumentsDerivativeFairValueMeasurementDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#FairValueofFinancialInstrumentsDerivativeFairValueMeasurementDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/FairValueofFinancialInstrumentsDerivativeFairValueMeasurementDetails" xlink:type="extended" id="i815ba25428a143bba47a2bfd772a92a5_FairValueofFinancialInstrumentsDerivativeFairValueMeasurementDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueOptionQuantitativeDisclosuresLineItems_2ad2cd4a-526a-492a-b1a2-a89a5c273b60" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueOptionQuantitativeDisclosuresLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsFairValueDisclosureAbstract_f4ab7ea1-7761-47a3-a6c9-d85fc3264b6c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AssetsFairValueDisclosureAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueOptionQuantitativeDisclosuresLineItems_2ad2cd4a-526a-492a-b1a2-a89a5c273b60" xlink:to="loc_us-gaap_AssetsFairValueDisclosureAbstract_f4ab7ea1-7761-47a3-a6c9-d85fc3264b6c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFairValueOfDerivativeAsset_2d370777-6559-4e10-845a-0fb31b568740" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeFairValueOfDerivativeAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_f4ab7ea1-7761-47a3-a6c9-d85fc3264b6c" xlink:to="loc_us-gaap_DerivativeFairValueOfDerivativeAsset_2d370777-6559-4e10-845a-0fb31b568740" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesFairValueDisclosureAbstract_80164f4d-fda0-4758-a055-f50cd616af12" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LiabilitiesFairValueDisclosureAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueOptionQuantitativeDisclosuresLineItems_2ad2cd4a-526a-492a-b1a2-a89a5c273b60" xlink:to="loc_us-gaap_LiabilitiesFairValueDisclosureAbstract_80164f4d-fda0-4758-a055-f50cd616af12" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFairValueOfDerivativeLiability_a59919fc-4311-4d90-8087-c16809e4e7bb" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeFairValueOfDerivativeLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesFairValueDisclosureAbstract_80164f4d-fda0-4758-a055-f50cd616af12" xlink:to="loc_us-gaap_DerivativeFairValueOfDerivativeLiability_a59919fc-4311-4d90-8087-c16809e4e7bb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsQuantitativeInformationAbstract_e3dfa9e7-6346-4ca5-bd87-d9f70aacdbdb" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueInputsQuantitativeInformationAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueOptionQuantitativeDisclosuresLineItems_2ad2cd4a-526a-492a-b1a2-a89a5c273b60" xlink:to="loc_us-gaap_FairValueInputsQuantitativeInformationAbstract_e3dfa9e7-6346-4ca5-bd87-d9f70aacdbdb" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeForwardPrice_01eea0c5-9b2c-4a00-8b47-3d1d129c994a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeForwardPrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueInputsQuantitativeInformationAbstract_e3dfa9e7-6346-4ca5-bd87-d9f70aacdbdb" xlink:to="loc_us-gaap_DerivativeForwardPrice_01eea0c5-9b2c-4a00-8b47-3d1d129c994a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_DerivativeAuctionPrice_3a4df8c8-3455-4acd-b0b2-5e1171d0860d" xlink:href="nrg-20201231.xsd#nrg_DerivativeAuctionPrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueInputsQuantitativeInformationAbstract_e3dfa9e7-6346-4ca5-bd87-d9f70aacdbdb" xlink:to="loc_nrg_DerivativeAuctionPrice_3a4df8c8-3455-4acd-b0b2-5e1171d0860d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeCollateralRightToReclaimCash_fb6736f8-a71a-47a4-a7a8-91e2dc742bf2" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeCollateralRightToReclaimCash"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueOptionQuantitativeDisclosuresLineItems_2ad2cd4a-526a-492a-b1a2-a89a5c273b60" xlink:to="loc_us-gaap_DerivativeCollateralRightToReclaimCash_fb6736f8-a71a-47a4-a7a8-91e2dc742bf2" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeCollateralObligationToReturnCash_160d077c-88e3-49d8-acea-ede5625785c2" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeCollateralObligationToReturnCash"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueOptionQuantitativeDisclosuresLineItems_2ad2cd4a-526a-492a-b1a2-a89a5c273b60" xlink:to="loc_us-gaap_DerivativeCollateralObligationToReturnCash_160d077c-88e3-49d8-acea-ede5625785c2" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_e64208b2-e015-48bc-885f-461446b611ea" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueOptionQuantitativeDisclosuresLineItems_2ad2cd4a-526a-492a-b1a2-a89a5c273b60" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_e64208b2-e015-48bc-885f-461446b611ea" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_9d35ba64-8911-4eea-acba-1bf96967ee9e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_e64208b2-e015-48bc-885f-461446b611ea" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_9d35ba64-8911-4eea-acba-1bf96967ee9e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_9d35ba64-8911-4eea-acba-1bf96967ee9e_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_9d35ba64-8911-4eea-acba-1bf96967ee9e" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_9d35ba64-8911-4eea-acba-1bf96967ee9e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_854688fe-9974-49ac-acec-35b3ffb2b901" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_9d35ba64-8911-4eea-acba-1bf96967ee9e" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_854688fe-9974-49ac-acec-35b3ffb2b901" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommodityContractMember_05137c89-0e10-4ea4-adfe-3c2262737424" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommodityContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_854688fe-9974-49ac-acec-35b3ffb2b901" xlink:to="loc_us-gaap_CommodityContractMember_05137c89-0e10-4ea4-adfe-3c2262737424" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByMeasurementFrequencyAxis_bec714a9-e8de-4367-ab92-fefb3c340aa5" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueByMeasurementFrequencyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_e64208b2-e015-48bc-885f-461446b611ea" xlink:to="loc_us-gaap_FairValueByMeasurementFrequencyAxis_bec714a9-e8de-4367-ab92-fefb3c340aa5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_bec714a9-e8de-4367-ab92-fefb3c340aa5_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_bec714a9-e8de-4367-ab92-fefb3c340aa5" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_bec714a9-e8de-4367-ab92-fefb3c340aa5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_b6b81571-3f08-4aac-ac3d-48b2f55d5b71" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_bec714a9-e8de-4367-ab92-fefb3c340aa5" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_b6b81571-3f08-4aac-ac3d-48b2f55d5b71" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsRecurringMember_336c10ef-dda9-4927-8796-3d5991061749" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueMeasurementsRecurringMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementFrequencyDomain_b6b81571-3f08-4aac-ac3d-48b2f55d5b71" xlink:to="loc_us-gaap_FairValueMeasurementsRecurringMember_336c10ef-dda9-4927-8796-3d5991061749" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_DerivativesByUnderlyingAssetsAxis_d7208147-791f-439c-838b-d7d4027c585d" xlink:href="nrg-20201231.xsd#nrg_DerivativesByUnderlyingAssetsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_e64208b2-e015-48bc-885f-461446b611ea" xlink:to="loc_nrg_DerivativesByUnderlyingAssetsAxis_d7208147-791f-439c-838b-d7d4027c585d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_UnderlyingAssetsDomain_d7208147-791f-439c-838b-d7d4027c585d_default" xlink:href="nrg-20201231.xsd#nrg_UnderlyingAssetsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_nrg_DerivativesByUnderlyingAssetsAxis_d7208147-791f-439c-838b-d7d4027c585d" xlink:to="loc_nrg_UnderlyingAssetsDomain_d7208147-791f-439c-838b-d7d4027c585d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_UnderlyingAssetsDomain_45d15822-417f-4074-9c91-819a9fc91047" xlink:href="nrg-20201231.xsd#nrg_UnderlyingAssetsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_nrg_DerivativesByUnderlyingAssetsAxis_d7208147-791f-439c-838b-d7d4027c585d" xlink:to="loc_nrg_UnderlyingAssetsDomain_45d15822-417f-4074-9c91-819a9fc91047" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_PowerContractsMember_2637df17-ee1f-4bcb-94b7-3522d8ed668c" xlink:href="nrg-20201231.xsd#nrg_PowerContractsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_UnderlyingAssetsDomain_45d15822-417f-4074-9c91-819a9fc91047" xlink:to="loc_nrg_PowerContractsMember_2637df17-ee1f-4bcb-94b7-3522d8ed668c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_FinancialTransmissionRightsMember_a887fb10-58da-47ba-b14b-bc94cc77e005" xlink:href="nrg-20201231.xsd#nrg_FinancialTransmissionRightsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_UnderlyingAssetsDomain_45d15822-417f-4074-9c91-819a9fc91047" xlink:to="loc_nrg_FinancialTransmissionRightsMember_a887fb10-58da-47ba-b14b-bc94cc77e005" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_8572fd57-c602-43ff-bcc2-8bbfcdf7bb67" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_e64208b2-e015-48bc-885f-461446b611ea" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_8572fd57-c602-43ff-bcc2-8bbfcdf7bb67" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_8572fd57-c602-43ff-bcc2-8bbfcdf7bb67_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_8572fd57-c602-43ff-bcc2-8bbfcdf7bb67" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_8572fd57-c602-43ff-bcc2-8bbfcdf7bb67_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_9b01c500-4b54-4b99-9fb3-639866554267" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_8572fd57-c602-43ff-bcc2-8bbfcdf7bb67" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_9b01c500-4b54-4b99-9fb3-639866554267" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_739ba3a0-4171-4997-b2d1-82bcf6ec2218" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_9b01c500-4b54-4b99-9fb3-639866554267" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_739ba3a0-4171-4997-b2d1-82bcf6ec2218" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_8be34b92-4574-42c5-8649-9bbd6a955677" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_e64208b2-e015-48bc-885f-461446b611ea" xlink:to="loc_srt_RangeAxis_8be34b92-4574-42c5-8649-9bbd6a955677" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_8be34b92-4574-42c5-8649-9bbd6a955677_default" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_8be34b92-4574-42c5-8649-9bbd6a955677" xlink:to="loc_srt_RangeMember_8be34b92-4574-42c5-8649-9bbd6a955677_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_1a7ccd75-948d-450d-b9e5-6185b5068aa7" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_8be34b92-4574-42c5-8649-9bbd6a955677" xlink:to="loc_srt_RangeMember_1a7ccd75-948d-450d-b9e5-6185b5068aa7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_c56765f1-245e-40ab-8fd1-1e2d1aa66eba" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_1a7ccd75-948d-450d-b9e5-6185b5068aa7" xlink:to="loc_srt_MinimumMember_c56765f1-245e-40ab-8fd1-1e2d1aa66eba" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_0bee57a9-98e5-46ac-8b87-a812362b0b01" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_1a7ccd75-948d-450d-b9e5-6185b5068aa7" xlink:to="loc_srt_MaximumMember_0bee57a9-98e5-46ac-8b87-a812362b0b01" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_WeightedAverageMember_9a55eae9-41d8-44a7-8cfb-d4112853b44d" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_WeightedAverageMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_1a7ccd75-948d-450d-b9e5-6185b5068aa7" xlink:to="loc_srt_WeightedAverageMember_9a55eae9-41d8-44a7-8cfb-d4112853b44d" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/FairValueofFinancialInstrumentsCounterpartyCreditRiskDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#FairValueofFinancialInstrumentsCounterpartyCreditRiskDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/FairValueofFinancialInstrumentsCounterpartyCreditRiskDetails" xlink:type="extended" id="ic70660f29b2d41b4b1bb9e7e033b9a89_FairValueofFinancialInstrumentsCounterpartyCreditRiskDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueConcentrationOfRiskFinancialStatementCaptionsLineItems_d68bb546-5299-459a-a549-2b5ebcc3c72c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueConcentrationOfRiskFinancialStatementCaptionsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_AmountOfCreditExposureToSignificantPortionOfAllCounterparties_7dcbd8b8-56cb-4b09-ad5a-10716657e03e" xlink:href="nrg-20201231.xsd#nrg_AmountOfCreditExposureToSignificantPortionOfAllCounterparties"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueConcentrationOfRiskFinancialStatementCaptionsLineItems_d68bb546-5299-459a-a549-2b5ebcc3c72c" xlink:to="loc_nrg_AmountOfCreditExposureToSignificantPortionOfAllCounterparties_7dcbd8b8-56cb-4b09-ad5a-10716657e03e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_CollateralHeldCashAndLettersOfCredit_e5fe127b-737c-41c6-a301-44c1ea22ae99" xlink:href="nrg-20201231.xsd#nrg_CollateralHeldCashAndLettersOfCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueConcentrationOfRiskFinancialStatementCaptionsLineItems_d68bb546-5299-459a-a549-2b5ebcc3c72c" xlink:to="loc_nrg_CollateralHeldCashAndLettersOfCredit_e5fe127b-737c-41c6-a301-44c1ea22ae99" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_NetCreditExposure_bbe6c54d-5fe4-4da7-9d18-6f07deacb809" xlink:href="nrg-20201231.xsd#nrg_NetCreditExposure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueConcentrationOfRiskFinancialStatementCaptionsLineItems_d68bb546-5299-459a-a549-2b5ebcc3c72c" xlink:to="loc_nrg_NetCreditExposure_bbe6c54d-5fe4-4da7-9d18-6f07deacb809" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_CounterpartyCreditRiskExposurePercentageOfCreditRiskRollOff_4e3b4727-981f-4bbe-a0bd-75b3f1a10376" xlink:href="nrg-20201231.xsd#nrg_CounterpartyCreditRiskExposurePercentageOfCreditRiskRollOff"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueConcentrationOfRiskFinancialStatementCaptionsLineItems_d68bb546-5299-459a-a549-2b5ebcc3c72c" xlink:to="loc_nrg_CounterpartyCreditRiskExposurePercentageOfCreditRiskRollOff_4e3b4727-981f-4bbe-a0bd-75b3f1a10376" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_CreditDerivativeMaximumNetExposurePercentage_efc518e9-397f-4a27-8960-42dfc16f9b83" xlink:href="nrg-20201231.xsd#nrg_CreditDerivativeMaximumNetExposurePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueConcentrationOfRiskFinancialStatementCaptionsLineItems_d68bb546-5299-459a-a549-2b5ebcc3c72c" xlink:to="loc_nrg_CreditDerivativeMaximumNetExposurePercentage_efc518e9-397f-4a27-8960-42dfc16f9b83" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_NumberOfWholesaleCounterpartiesWithCreditRiskExposure_3e5b135b-2e24-46e6-8a02-c1689c8eacde" xlink:href="nrg-20201231.xsd#nrg_NumberOfWholesaleCounterpartiesWithCreditRiskExposure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueConcentrationOfRiskFinancialStatementCaptionsLineItems_d68bb546-5299-459a-a549-2b5ebcc3c72c" xlink:to="loc_nrg_NumberOfWholesaleCounterpartiesWithCreditRiskExposure_3e5b135b-2e24-46e6-8a02-c1689c8eacde" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_CounterpartyCreditRiskExposurePercentageThreshold_9f18466c-9c41-476f-b149-1f6d4b80267f" xlink:href="nrg-20201231.xsd#nrg_CounterpartyCreditRiskExposurePercentageThreshold"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueConcentrationOfRiskFinancialStatementCaptionsLineItems_d68bb546-5299-459a-a549-2b5ebcc3c72c" xlink:to="loc_nrg_CounterpartyCreditRiskExposurePercentageThreshold_9f18466c-9c41-476f-b149-1f6d4b80267f" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_EstimatedCounterpartyCreditRiskExposureToCertainCounterparties_3a6b2c2c-41c0-4867-a512-592d4a81459f" xlink:href="nrg-20201231.xsd#nrg_EstimatedCounterpartyCreditRiskExposureToCertainCounterparties"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueConcentrationOfRiskFinancialStatementCaptionsLineItems_d68bb546-5299-459a-a549-2b5ebcc3c72c" xlink:to="loc_nrg_EstimatedCounterpartyCreditRiskExposureToCertainCounterparties_3a6b2c2c-41c0-4867-a512-592d4a81459f" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_EstimatedCounterpartyCreditRiskExposureToCertainCounterpartiesPeriod_6b6d689f-6288-4eb7-a483-190eae61b18b" xlink:href="nrg-20201231.xsd#nrg_EstimatedCounterpartyCreditRiskExposureToCertainCounterpartiesPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueConcentrationOfRiskFinancialStatementCaptionsLineItems_d68bb546-5299-459a-a549-2b5ebcc3c72c" xlink:to="loc_nrg_EstimatedCounterpartyCreditRiskExposureToCertainCounterpartiesPeriod_6b6d689f-6288-4eb7-a483-190eae61b18b" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProvisionForDoubtfulAccounts_7665c999-20a6-438a-9db1-e71021269716" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ProvisionForDoubtfulAccounts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueConcentrationOfRiskFinancialStatementCaptionsLineItems_d68bb546-5299-459a-a549-2b5ebcc3c72c" xlink:to="loc_us-gaap_ProvisionForDoubtfulAccounts_7665c999-20a6-438a-9db1-e71021269716" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueConcentrationOfRiskTable_d9a77b83-8aad-49c7-8dbf-88b512b36c39" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueConcentrationOfRiskTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueConcentrationOfRiskFinancialStatementCaptionsLineItems_d68bb546-5299-459a-a549-2b5ebcc3c72c" xlink:to="loc_us-gaap_FairValueConcentrationOfRiskTable_d9a77b83-8aad-49c7-8dbf-88b512b36c39" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_CounterpartyRiskByInstitutionAxis_656bb2b5-49ea-48ce-9d20-b9c626cf6c95" xlink:href="nrg-20201231.xsd#nrg_CounterpartyRiskByInstitutionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueConcentrationOfRiskTable_d9a77b83-8aad-49c7-8dbf-88b512b36c39" xlink:to="loc_nrg_CounterpartyRiskByInstitutionAxis_656bb2b5-49ea-48ce-9d20-b9c626cf6c95" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_CounterpartyRiskByInstitutionDomain_656bb2b5-49ea-48ce-9d20-b9c626cf6c95_default" xlink:href="nrg-20201231.xsd#nrg_CounterpartyRiskByInstitutionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_nrg_CounterpartyRiskByInstitutionAxis_656bb2b5-49ea-48ce-9d20-b9c626cf6c95" xlink:to="loc_nrg_CounterpartyRiskByInstitutionDomain_656bb2b5-49ea-48ce-9d20-b9c626cf6c95_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_CounterpartyRiskByInstitutionDomain_c71f7d6c-915b-45ea-9871-8ec1c8142bfb" xlink:href="nrg-20201231.xsd#nrg_CounterpartyRiskByInstitutionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_nrg_CounterpartyRiskByInstitutionAxis_656bb2b5-49ea-48ce-9d20-b9c626cf6c95" xlink:to="loc_nrg_CounterpartyRiskByInstitutionDomain_c71f7d6c-915b-45ea-9871-8ec1c8142bfb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_UtilitiesEnergyMerchantsMarketersAndOtherMember_34358ab6-a956-4afc-864d-d3ed660f932d" xlink:href="nrg-20201231.xsd#nrg_UtilitiesEnergyMerchantsMarketersAndOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_CounterpartyRiskByInstitutionDomain_c71f7d6c-915b-45ea-9871-8ec1c8142bfb" xlink:to="loc_nrg_UtilitiesEnergyMerchantsMarketersAndOtherMember_34358ab6-a956-4afc-864d-d3ed660f932d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_FinancialInstitutionsMember_dd010a00-b108-4707-9a54-fdf92147df9a" xlink:href="nrg-20201231.xsd#nrg_FinancialInstitutionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_CounterpartyRiskByInstitutionDomain_c71f7d6c-915b-45ea-9871-8ec1c8142bfb" xlink:to="loc_nrg_FinancialInstitutionsMember_dd010a00-b108-4707-9a54-fdf92147df9a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_CounterpartyRiskByInvestmentGradeAxis_8c04f1f2-8134-4e80-b89c-a7dc9034e508" xlink:href="nrg-20201231.xsd#nrg_CounterpartyRiskByInvestmentGradeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueConcentrationOfRiskTable_d9a77b83-8aad-49c7-8dbf-88b512b36c39" xlink:to="loc_nrg_CounterpartyRiskByInvestmentGradeAxis_8c04f1f2-8134-4e80-b89c-a7dc9034e508" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_CounterpartyRiskByInvestmentGradeDomain_8c04f1f2-8134-4e80-b89c-a7dc9034e508_default" xlink:href="nrg-20201231.xsd#nrg_CounterpartyRiskByInvestmentGradeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_nrg_CounterpartyRiskByInvestmentGradeAxis_8c04f1f2-8134-4e80-b89c-a7dc9034e508" xlink:to="loc_nrg_CounterpartyRiskByInvestmentGradeDomain_8c04f1f2-8134-4e80-b89c-a7dc9034e508_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_CounterpartyRiskByInvestmentGradeDomain_ad5806d6-0b6f-4618-8542-16dc6b61fe8d" xlink:href="nrg-20201231.xsd#nrg_CounterpartyRiskByInvestmentGradeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_nrg_CounterpartyRiskByInvestmentGradeAxis_8c04f1f2-8134-4e80-b89c-a7dc9034e508" xlink:to="loc_nrg_CounterpartyRiskByInvestmentGradeDomain_ad5806d6-0b6f-4618-8542-16dc6b61fe8d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ExternalCreditRatingInvestmentGradeMember_3f2305a8-7ca0-41a1-8674-2efefa6c764e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ExternalCreditRatingInvestmentGradeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_CounterpartyRiskByInvestmentGradeDomain_ad5806d6-0b6f-4618-8542-16dc6b61fe8d" xlink:to="loc_us-gaap_ExternalCreditRatingInvestmentGradeMember_3f2305a8-7ca0-41a1-8674-2efefa6c764e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_ExternalCreditRatingNotRatedMember_11feb37a-8bb0-4932-90e9-2593fc09d3c3" xlink:href="nrg-20201231.xsd#nrg_ExternalCreditRatingNotRatedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_CounterpartyRiskByInvestmentGradeDomain_ad5806d6-0b6f-4618-8542-16dc6b61fe8d" xlink:to="loc_nrg_ExternalCreditRatingNotRatedMember_11feb37a-8bb0-4932-90e9-2593fc09d3c3" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/AccountingforDerivativeInstrumentsandHedgingActivities" xlink:type="simple" xlink:href="nrg-20201231.xsd#AccountingforDerivativeInstrumentsandHedgingActivities"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/AccountingforDerivativeInstrumentsandHedgingActivities" xlink:type="extended" id="ia7758630ea4d47a4b2c222386fe57bd5_AccountingforDerivativeInstrumentsandHedgingActivities"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/AccountingforDerivativeInstrumentsandHedgingActivitiesTables" xlink:type="simple" xlink:href="nrg-20201231.xsd#AccountingforDerivativeInstrumentsandHedgingActivitiesTables"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/AccountingforDerivativeInstrumentsandHedgingActivitiesTables" xlink:type="extended" id="i228bfe9f067948578f58175aaf78b0c9_AccountingforDerivativeInstrumentsandHedgingActivitiesTables"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/AccountingforDerivativeInstrumentsandHedgingActivitiesNetNotionalVolumeBuySellofOpenDerivativeTransactionsDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#AccountingforDerivativeInstrumentsandHedgingActivitiesNetNotionalVolumeBuySellofOpenDerivativeTransactionsDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/AccountingforDerivativeInstrumentsandHedgingActivitiesNetNotionalVolumeBuySellofOpenDerivativeTransactionsDetails" xlink:type="extended" id="i2143982a2dfd41a3a6f1f3f98afe4ab4_AccountingforDerivativeInstrumentsandHedgingActivitiesNetNotionalVolumeBuySellofOpenDerivativeTransactionsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLineItems_0c13c748-5b43-42a8-92af-772e7127812d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeNonmonetaryNotionalAmountMass_ecced43d-ac1a-408a-b389-b0c3af4967e9" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeNonmonetaryNotionalAmountMass"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_0c13c748-5b43-42a8-92af-772e7127812d" xlink:to="loc_us-gaap_DerivativeNonmonetaryNotionalAmountMass_ecced43d-ac1a-408a-b389-b0c3af4967e9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_DerivativeNonmonetaryNotionalAmountOther_8bdc85a3-811b-4015-ba9e-7bbc8b0d65f0" xlink:href="nrg-20201231.xsd#nrg_DerivativeNonmonetaryNotionalAmountOther"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_0c13c748-5b43-42a8-92af-772e7127812d" xlink:to="loc_nrg_DerivativeNonmonetaryNotionalAmountOther_8bdc85a3-811b-4015-ba9e-7bbc8b0d65f0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeNonmonetaryNotionalAmountEnergyMeasure_8881fa9d-9abf-43ea-b37e-7e3a87608bf4" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeNonmonetaryNotionalAmountEnergyMeasure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_0c13c748-5b43-42a8-92af-772e7127812d" xlink:to="loc_us-gaap_DerivativeNonmonetaryNotionalAmountEnergyMeasure_8881fa9d-9abf-43ea-b37e-7e3a87608bf4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeTable_8ffb40f2-a8f4-4ffc-958c-f71ec8fcbe9e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeLineItems_0c13c748-5b43-42a8-92af-772e7127812d" xlink:to="loc_us-gaap_DerivativeTable_8ffb40f2-a8f4-4ffc-958c-f71ec8fcbe9e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PositionAxis_4c4603aa-bc73-4755-bed2-d268a4b9d404" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PositionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_8ffb40f2-a8f4-4ffc-958c-f71ec8fcbe9e" xlink:to="loc_us-gaap_PositionAxis_4c4603aa-bc73-4755-bed2-d268a4b9d404" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PositionDomain_4c4603aa-bc73-4755-bed2-d268a4b9d404_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PositionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PositionAxis_4c4603aa-bc73-4755-bed2-d268a4b9d404" xlink:to="loc_us-gaap_PositionDomain_4c4603aa-bc73-4755-bed2-d268a4b9d404_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PositionDomain_6876b8ce-ce78-4de5-b9da-2e1717ad1e38" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PositionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PositionAxis_4c4603aa-bc73-4755-bed2-d268a4b9d404" xlink:to="loc_us-gaap_PositionDomain_6876b8ce-ce78-4de5-b9da-2e1717ad1e38" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongMember_d0c7b715-ede2-4fd0-9c6c-f0ab7e6086fe" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PositionDomain_6876b8ce-ce78-4de5-b9da-2e1717ad1e38" xlink:to="loc_us-gaap_LongMember_d0c7b715-ede2-4fd0-9c6c-f0ab7e6086fe" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortMember_b8948d01-a7eb-4a4b-83aa-88cedd2fc970" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShortMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PositionDomain_6876b8ce-ce78-4de5-b9da-2e1717ad1e38" xlink:to="loc_us-gaap_ShortMember_b8948d01-a7eb-4a4b-83aa-88cedd2fc970" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnderlyingAssetClassAxis_954c09fd-c2c6-4554-9c69-703d00d74636" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_UnderlyingAssetClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_8ffb40f2-a8f4-4ffc-958c-f71ec8fcbe9e" xlink:to="loc_us-gaap_UnderlyingAssetClassAxis_954c09fd-c2c6-4554-9c69-703d00d74636" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnderlyingAssetClassDomain_954c09fd-c2c6-4554-9c69-703d00d74636_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_UnderlyingAssetClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_UnderlyingAssetClassAxis_954c09fd-c2c6-4554-9c69-703d00d74636" xlink:to="loc_us-gaap_UnderlyingAssetClassDomain_954c09fd-c2c6-4554-9c69-703d00d74636_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnderlyingAssetClassDomain_3d5e9eb6-79cf-4d69-aa7d-d9e985b90d52" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_UnderlyingAssetClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_UnderlyingAssetClassAxis_954c09fd-c2c6-4554-9c69-703d00d74636" xlink:to="loc_us-gaap_UnderlyingAssetClassDomain_3d5e9eb6-79cf-4d69-aa7d-d9e985b90d52" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_EmissionsMember_25bac237-01b6-4e99-ba55-361c22fc16a7" xlink:href="nrg-20201231.xsd#nrg_EmissionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnderlyingAssetClassDomain_3d5e9eb6-79cf-4d69-aa7d-d9e985b90d52" xlink:to="loc_nrg_EmissionsMember_25bac237-01b6-4e99-ba55-361c22fc16a7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_RenewableEnergyCertificatesMember_fb26803d-8f09-4ed5-b3f5-2684b895209e" xlink:href="nrg-20201231.xsd#nrg_RenewableEnergyCertificatesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnderlyingAssetClassDomain_3d5e9eb6-79cf-4d69-aa7d-d9e985b90d52" xlink:to="loc_nrg_RenewableEnergyCertificatesMember_fb26803d-8f09-4ed5-b3f5-2684b895209e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_CoalMember_33d6cea7-9e43-4ef5-9977-4fd73d189490" xlink:href="nrg-20201231.xsd#nrg_CoalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnderlyingAssetClassDomain_3d5e9eb6-79cf-4d69-aa7d-d9e985b90d52" xlink:to="loc_nrg_CoalMember_33d6cea7-9e43-4ef5-9977-4fd73d189490" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_NaturalGasMember_e0032bfe-a2b4-46a3-b28c-fccc126563d3" xlink:href="nrg-20201231.xsd#nrg_NaturalGasMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnderlyingAssetClassDomain_3d5e9eb6-79cf-4d69-aa7d-d9e985b90d52" xlink:to="loc_nrg_NaturalGasMember_e0032bfe-a2b4-46a3-b28c-fccc126563d3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_PowerMember_b514023b-9b52-4ff0-b67b-b136cb3a9f4d" xlink:href="nrg-20201231.xsd#nrg_PowerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnderlyingAssetClassDomain_3d5e9eb6-79cf-4d69-aa7d-d9e985b90d52" xlink:to="loc_nrg_PowerMember_b514023b-9b52-4ff0-b67b-b136cb3a9f4d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapacityMember_73502724-80a3-44ab-9d82-0c4274b52bc8" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CapacityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnderlyingAssetClassDomain_3d5e9eb6-79cf-4d69-aa7d-d9e985b90d52" xlink:to="loc_us-gaap_CapacityMember_73502724-80a3-44ab-9d82-0c4274b52bc8" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/AccountingforDerivativeInstrumentsandHedgingActivitiesFairValueWithintheDerivativeInstrumentValuationDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#AccountingforDerivativeInstrumentsandHedgingActivitiesFairValueWithintheDerivativeInstrumentValuationDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/AccountingforDerivativeInstrumentsandHedgingActivitiesFairValueWithintheDerivativeInstrumentValuationDetails" xlink:type="extended" id="ic0977d5a634f4d598c8e926efd2850d0_AccountingforDerivativeInstrumentsandHedgingActivitiesFairValueWithintheDerivativeInstrumentValuationDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLineItems_f46f5b53-dbb2-49ef-bfc1-384ca161af25" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFairValueOfDerivativeAsset_97763581-a83b-4734-af60-298aad9f1f30" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeFairValueOfDerivativeAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_f46f5b53-dbb2-49ef-bfc1-384ca161af25" xlink:to="loc_us-gaap_DerivativeFairValueOfDerivativeAsset_97763581-a83b-4734-af60-298aad9f1f30" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFairValueOfDerivativeLiability_481549c4-0f04-471f-89d2-b8da219dec80" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeFairValueOfDerivativeLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_f46f5b53-dbb2-49ef-bfc1-384ca161af25" xlink:to="loc_us-gaap_DerivativeFairValueOfDerivativeLiability_481549c4-0f04-471f-89d2-b8da219dec80" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeTable_1695d5d7-a7df-4148-9c7a-c28b64ad147d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeLineItems_f46f5b53-dbb2-49ef-bfc1-384ca161af25" xlink:to="loc_us-gaap_DerivativeTable_1695d5d7-a7df-4148-9c7a-c28b64ad147d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationAxis_5cfa9d37-e675-40aa-adee-1dfa2924d382" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_HedgingDesignationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_1695d5d7-a7df-4148-9c7a-c28b64ad147d" xlink:to="loc_us-gaap_HedgingDesignationAxis_5cfa9d37-e675-40aa-adee-1dfa2924d382" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_5cfa9d37-e675-40aa-adee-1dfa2924d382_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_HedgingDesignationAxis_5cfa9d37-e675-40aa-adee-1dfa2924d382" xlink:to="loc_us-gaap_HedgingDesignationDomain_5cfa9d37-e675-40aa-adee-1dfa2924d382_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_f57be1db-98ec-489f-af4e-a254993dfb11" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_HedgingDesignationAxis_5cfa9d37-e675-40aa-adee-1dfa2924d382" xlink:to="loc_us-gaap_HedgingDesignationDomain_f57be1db-98ec-489f-af4e-a254993dfb11" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NondesignatedMember_2448ab80-cbf7-4ac8-9893-9dc719256b71" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NondesignatedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingDesignationDomain_f57be1db-98ec-489f-af4e-a254993dfb11" xlink:to="loc_us-gaap_NondesignatedMember_2448ab80-cbf7-4ac8-9893-9dc719256b71" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_21f535af-d814-44db-950e-34f5f50627e1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_1695d5d7-a7df-4148-9c7a-c28b64ad147d" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_21f535af-d814-44db-950e-34f5f50627e1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_21f535af-d814-44db-950e-34f5f50627e1_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_21f535af-d814-44db-950e-34f5f50627e1" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_21f535af-d814-44db-950e-34f5f50627e1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_b8018866-9a0f-4c4e-962d-394cd094fd18" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_21f535af-d814-44db-950e-34f5f50627e1" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_b8018866-9a0f-4c4e-962d-394cd094fd18" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_CommodityContractCurrentMember_0826c8e1-9f1d-4ae8-98d7-7bcd8ab8d079" xlink:href="nrg-20201231.xsd#nrg_CommodityContractCurrentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_b8018866-9a0f-4c4e-962d-394cd094fd18" xlink:to="loc_nrg_CommodityContractCurrentMember_0826c8e1-9f1d-4ae8-98d7-7bcd8ab8d079" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_CommodityContractNonCurrentMember_f9769d33-5376-4a68-9f6b-23d68fcea13f" xlink:href="nrg-20201231.xsd#nrg_CommodityContractNonCurrentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_b8018866-9a0f-4c4e-962d-394cd094fd18" xlink:to="loc_nrg_CommodityContractNonCurrentMember_f9769d33-5376-4a68-9f6b-23d68fcea13f" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/AccountingforDerivativeInstrumentsandHedgingActivitiesOffsettingofDerivativesbyCounterpartyMasterAgreementlevelandCollateralReceivedDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#AccountingforDerivativeInstrumentsandHedgingActivitiesOffsettingofDerivativesbyCounterpartyMasterAgreementlevelandCollateralReceivedDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/AccountingforDerivativeInstrumentsandHedgingActivitiesOffsettingofDerivativesbyCounterpartyMasterAgreementlevelandCollateralReceivedDetails" xlink:type="extended" id="i1980ebfdfa5b459c82edce570fe1f9d9_AccountingforDerivativeInstrumentsandHedgingActivitiesOffsettingofDerivativesbyCounterpartyMasterAgreementlevelandCollateralReceivedDetails">
    <link:loc xlink:type="locator" xlink:label="loc_nrg_OffsettingAssetsAndLiabilitiesLineItems_d6e599e1-f021-4b87-a48a-ee840ae0b027" xlink:href="nrg-20201231.xsd#nrg_OffsettingAssetsAndLiabilitiesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFairValueOfDerivativeAsset_f51760d7-5e54-4f11-bbc8-22b7b21a55ed" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeFairValueOfDerivativeAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_OffsettingAssetsAndLiabilitiesLineItems_d6e599e1-f021-4b87-a48a-ee840ae0b027" xlink:to="loc_us-gaap_DerivativeFairValueOfDerivativeAsset_f51760d7-5e54-4f11-bbc8-22b7b21a55ed" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssetFairValueGrossLiability_ed8e4d14-1b1a-40f8-8d85-521a6107fb29" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeAssetFairValueGrossLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_OffsettingAssetsAndLiabilitiesLineItems_d6e599e1-f021-4b87-a48a-ee840ae0b027" xlink:to="loc_us-gaap_DerivativeAssetFairValueGrossLiability_ed8e4d14-1b1a-40f8-8d85-521a6107fb29" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeCollateralObligationToReturnCash_0c8f2e30-9a77-4808-bd0a-87eeff253dc9" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeCollateralObligationToReturnCash"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_OffsettingAssetsAndLiabilitiesLineItems_d6e599e1-f021-4b87-a48a-ee840ae0b027" xlink:to="loc_us-gaap_DerivativeCollateralObligationToReturnCash_0c8f2e30-9a77-4808-bd0a-87eeff253dc9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFairValueOfDerivativeAssetAmountOffsetAgainstCollateral_091c1921-a2c2-4e76-a67c-25a99cccfc2e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeFairValueOfDerivativeAssetAmountOffsetAgainstCollateral"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_OffsettingAssetsAndLiabilitiesLineItems_d6e599e1-f021-4b87-a48a-ee840ae0b027" xlink:to="loc_us-gaap_DerivativeFairValueOfDerivativeAssetAmountOffsetAgainstCollateral_091c1921-a2c2-4e76-a67c-25a99cccfc2e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFairValueOfDerivativeLiability_9ee39310-4132-4397-a5fe-0e2ff7130d2f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeFairValueOfDerivativeLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_OffsettingAssetsAndLiabilitiesLineItems_d6e599e1-f021-4b87-a48a-ee840ae0b027" xlink:to="loc_us-gaap_DerivativeFairValueOfDerivativeLiability_9ee39310-4132-4397-a5fe-0e2ff7130d2f" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilityFairValueGrossAsset_12e9e8c4-6448-4caf-a163-2df49aadb80b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeLiabilityFairValueGrossAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_OffsettingAssetsAndLiabilitiesLineItems_d6e599e1-f021-4b87-a48a-ee840ae0b027" xlink:to="loc_us-gaap_DerivativeLiabilityFairValueGrossAsset_12e9e8c4-6448-4caf-a163-2df49aadb80b" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeCollateralRightToReclaimCash_b689cc10-d56a-425b-83ca-df09efefbe03" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeCollateralRightToReclaimCash"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_OffsettingAssetsAndLiabilitiesLineItems_d6e599e1-f021-4b87-a48a-ee840ae0b027" xlink:to="loc_us-gaap_DerivativeCollateralRightToReclaimCash_b689cc10-d56a-425b-83ca-df09efefbe03" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFairValueOfDerivativeLiabilityAmountOffsetAgainstCollateral_efb16a6c-2d52-49cb-98a5-b8ec48dabede" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeFairValueOfDerivativeLiabilityAmountOffsetAgainstCollateral"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_OffsettingAssetsAndLiabilitiesLineItems_d6e599e1-f021-4b87-a48a-ee840ae0b027" xlink:to="loc_us-gaap_DerivativeFairValueOfDerivativeLiabilityAmountOffsetAgainstCollateral_efb16a6c-2d52-49cb-98a5-b8ec48dabede" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_FairValueofGrossDerivativeAssetsLiabilitiesNet_98762d71-36a0-4cb9-af70-c3baeba952e6" xlink:href="nrg-20201231.xsd#nrg_FairValueofGrossDerivativeAssetsLiabilitiesNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_OffsettingAssetsAndLiabilitiesLineItems_d6e599e1-f021-4b87-a48a-ee840ae0b027" xlink:to="loc_nrg_FairValueofGrossDerivativeAssetsLiabilitiesNet_98762d71-36a0-4cb9-af70-c3baeba952e6" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_DerivativeAssetFairValueGrossLiabilityNetOfDerivativeLiabilityFairValueGrossAsset_69e36939-a0d4-4588-9b31-b6ce03f3d905" xlink:href="nrg-20201231.xsd#nrg_DerivativeAssetFairValueGrossLiabilityNetOfDerivativeLiabilityFairValueGrossAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_OffsettingAssetsAndLiabilitiesLineItems_d6e599e1-f021-4b87-a48a-ee840ae0b027" xlink:to="loc_nrg_DerivativeAssetFairValueGrossLiabilityNetOfDerivativeLiabilityFairValueGrossAsset_69e36939-a0d4-4588-9b31-b6ce03f3d905" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_DerivativeCollateralObligationToReturnCashNetOfDerivativeCollateralRightToReclaimCash_8ed84b1e-57e4-463b-b99c-e9aa08164f30" xlink:href="nrg-20201231.xsd#nrg_DerivativeCollateralObligationToReturnCashNetOfDerivativeCollateralRightToReclaimCash"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_OffsettingAssetsAndLiabilitiesLineItems_d6e599e1-f021-4b87-a48a-ee840ae0b027" xlink:to="loc_nrg_DerivativeCollateralObligationToReturnCashNetOfDerivativeCollateralRightToReclaimCash_8ed84b1e-57e4-463b-b99c-e9aa08164f30" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_DerivativeAssetFairValueAmountOffsetAgainstCollateralNetOfDerivativeLiabilityFairValueAmountOffsetAgainstCollateral_dda867e7-3d7d-4cbd-bad7-ea5fa4730edc" xlink:href="nrg-20201231.xsd#nrg_DerivativeAssetFairValueAmountOffsetAgainstCollateralNetOfDerivativeLiabilityFairValueAmountOffsetAgainstCollateral"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_OffsettingAssetsAndLiabilitiesLineItems_d6e599e1-f021-4b87-a48a-ee840ae0b027" xlink:to="loc_nrg_DerivativeAssetFairValueAmountOffsetAgainstCollateralNetOfDerivativeLiabilityFairValueAmountOffsetAgainstCollateral_dda867e7-3d7d-4cbd-bad7-ea5fa4730edc" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeTable_960352da-499a-4fa3-8d31-cb8b0f9646d2" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_nrg_OffsettingAssetsAndLiabilitiesLineItems_d6e599e1-f021-4b87-a48a-ee840ae0b027" xlink:to="loc_us-gaap_DerivativeTable_960352da-499a-4fa3-8d31-cb8b0f9646d2" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_26dc386b-8ec1-4aaf-83a7-2aad6fb4db8a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_960352da-499a-4fa3-8d31-cb8b0f9646d2" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_26dc386b-8ec1-4aaf-83a7-2aad6fb4db8a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_26dc386b-8ec1-4aaf-83a7-2aad6fb4db8a_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_26dc386b-8ec1-4aaf-83a7-2aad6fb4db8a" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_26dc386b-8ec1-4aaf-83a7-2aad6fb4db8a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_59742070-ea3e-454c-aab2-eb4bfea1f8dc" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_26dc386b-8ec1-4aaf-83a7-2aad6fb4db8a" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_59742070-ea3e-454c-aab2-eb4bfea1f8dc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommodityContractMember_fd8188ae-0379-45f0-971d-80671724172f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommodityContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_59742070-ea3e-454c-aab2-eb4bfea1f8dc" xlink:to="loc_us-gaap_CommodityContractMember_fd8188ae-0379-45f0-971d-80671724172f" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/AccountingforDerivativeInstrumentsandHedgingActivitiesEffectonAccumulatedOCIBalanceAttributabletoCashFlowHedgeDerivativesNetDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#AccountingforDerivativeInstrumentsandHedgingActivitiesEffectonAccumulatedOCIBalanceAttributabletoCashFlowHedgeDerivativesNetDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/AccountingforDerivativeInstrumentsandHedgingActivitiesEffectonAccumulatedOCIBalanceAttributabletoCashFlowHedgeDerivativesNetDetails" xlink:type="extended" id="i56856319084a4df4a9c225305dfce56e_AccountingforDerivativeInstrumentsandHedgingActivitiesEffectonAccumulatedOCIBalanceAttributabletoCashFlowHedgeDerivativesNetDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLineItems_dbb64760-12f3-4ace-938f-b4e22c603504" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNetAbstract_79d882d1-c12a-4208-a938-03df96d26103" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNetAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_dbb64760-12f3-4ace-938f-b4e22c603504" xlink:to="loc_us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNetAbstract_79d882d1-c12a-4208-a938-03df96d26103" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeRollForward_d9d041e5-4178-4da5-89d5-faa75fd2427a" xlink:href="nrg-20201231.xsd#nrg_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNetAbstract_79d882d1-c12a-4208-a938-03df96d26103" xlink:to="loc_nrg_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeRollForward_d9d041e5-4178-4da5-89d5-faa75fd2427a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_0df62750-c804-4d15-87c4-f07b6d16635e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeRollForward_d9d041e5-4178-4da5-89d5-faa75fd2427a" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_0df62750-c804-4d15-87c4-f07b6d16635e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossDerivativeExcludedComponentIncreaseDecreaseAfterAdjustmentsAndTax_fb3d740d-6b93-494c-aeb6-b9fa0d80abee" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossDerivativeExcludedComponentIncreaseDecreaseAfterAdjustmentsAndTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_0df62750-c804-4d15-87c4-f07b6d16635e" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossDerivativeExcludedComponentIncreaseDecreaseAfterAdjustmentsAndTax_fb3d740d-6b93-494c-aeb6-b9fa0d80abee" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationAfterTax_458ba389-af00-470d-a457-9e10c86bc007" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationAfterTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_0df62750-c804-4d15-87c4-f07b6d16635e" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationAfterTax_458ba389-af00-470d-a457-9e10c86bc007" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIDivestitureOfBusinessNetOfTax_4335d8f3-f81f-4905-8d70-87ef08f68a99" xlink:href="nrg-20201231.xsd#nrg_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIDivestitureOfBusinessNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeRollForward_d9d041e5-4178-4da5-89d5-faa75fd2427a" xlink:to="loc_nrg_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIDivestitureOfBusinessNetOfTax_4335d8f3-f81f-4905-8d70-87ef08f68a99" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_55c2b11b-699b-406e-b780-70a38510d8b0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeTable_6e13cce7-d68a-4cee-abf2-f437bc48feef" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeLineItems_dbb64760-12f3-4ace-938f-b4e22c603504" xlink:to="loc_us-gaap_DerivativeTable_6e13cce7-d68a-4cee-abf2-f437bc48feef" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_c2194504-4068-402a-8676-c97d0c5138cb" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_6e13cce7-d68a-4cee-abf2-f437bc48feef" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_c2194504-4068-402a-8676-c97d0c5138cb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_c2194504-4068-402a-8676-c97d0c5138cb_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_c2194504-4068-402a-8676-c97d0c5138cb" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_c2194504-4068-402a-8676-c97d0c5138cb_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_9539e03d-8d75-4b04-b52c-6cd63a129f1d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_c2194504-4068-402a-8676-c97d0c5138cb" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_9539e03d-8d75-4b04-b52c-6cd63a129f1d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateContractMember_7085ec84-2582-4187-9320-67cf6461464e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InterestRateContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_9539e03d-8d75-4b04-b52c-6cd63a129f1d" xlink:to="loc_us-gaap_InterestRateContractMember_7085ec84-2582-4187-9320-67cf6461464e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_39867469-c43b-473c-9650-0ae3ee81c431" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_6e13cce7-d68a-4cee-abf2-f437bc48feef" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_39867469-c43b-473c-9650-0ae3ee81c431" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_39867469-c43b-473c-9650-0ae3ee81c431_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_39867469-c43b-473c-9650-0ae3ee81c431" xlink:to="loc_us-gaap_EquityComponentDomain_39867469-c43b-473c-9650-0ae3ee81c431_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_c9598c98-397f-4c69-924f-4d637a31ed1b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_39867469-c43b-473c-9650-0ae3ee81c431" xlink:to="loc_us-gaap_EquityComponentDomain_c9598c98-397f-4c69-924f-4d637a31ed1b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AociIncludingPortionAttributableToNoncontrollingInterestMember_814d3f1c-4d50-441c-b07f-bef850879f03" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AociIncludingPortionAttributableToNoncontrollingInterestMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_c9598c98-397f-4c69-924f-4d637a31ed1b" xlink:to="loc_us-gaap_AociIncludingPortionAttributableToNoncontrollingInterestMember_814d3f1c-4d50-441c-b07f-bef850879f03" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedGainLossNetCashFlowHedgeParentMember_82149bd1-7ebc-4b5e-bdbc-51a929ff8aac" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccumulatedGainLossNetCashFlowHedgeParentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_c9598c98-397f-4c69-924f-4d637a31ed1b" xlink:to="loc_us-gaap_AccumulatedGainLossNetCashFlowHedgeParentMember_82149bd1-7ebc-4b5e-bdbc-51a929ff8aac" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember_84387630-58f5-41fa-9e37-799b1a61de1f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_c9598c98-397f-4c69-924f-4d637a31ed1b" xlink:to="loc_us-gaap_AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember_84387630-58f5-41fa-9e37-799b1a61de1f" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/AccountingforDerivativeInstrumentsandHedgingActivitiesNarrativeDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#AccountingforDerivativeInstrumentsandHedgingActivitiesNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/AccountingforDerivativeInstrumentsandHedgingActivitiesNarrativeDetails" xlink:type="extended" id="ia7ae688feacd4eb597ce55d69332903e_AccountingforDerivativeInstrumentsandHedgingActivitiesNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLineItems_6c33342a-9df1-45dd-9a5c-c6badafcdf7e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeNotionalAmount_8238c965-28bb-468c-8fb2-983453041e38" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeNotionalAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_6c33342a-9df1-45dd-9a5c-c6badafcdf7e" xlink:to="loc_us-gaap_DerivativeNotionalAmount_8238c965-28bb-468c-8fb2-983453041e38" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeGainOnDerivative_c49bac39-4ee3-4c08-bac9-fc79b5c1cba4" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeGainOnDerivative"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_6c33342a-9df1-45dd-9a5c-c6badafcdf7e" xlink:to="loc_us-gaap_DerivativeGainOnDerivative_c49bac39-4ee3-4c08-bac9-fc79b5c1cba4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeTable_3b9723a2-b2aa-49a3-b858-eda3bedced1a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeLineItems_6c33342a-9df1-45dd-9a5c-c6badafcdf7e" xlink:to="loc_us-gaap_DerivativeTable_3b9723a2-b2aa-49a3-b858-eda3bedced1a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_8023b4aa-be54-4f6e-b49d-04743822e880" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_3b9723a2-b2aa-49a3-b858-eda3bedced1a" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_8023b4aa-be54-4f6e-b49d-04743822e880" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_8023b4aa-be54-4f6e-b49d-04743822e880_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_8023b4aa-be54-4f6e-b49d-04743822e880" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_8023b4aa-be54-4f6e-b49d-04743822e880_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_baeae57e-5e51-4944-8e92-061220b3c1ec" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_8023b4aa-be54-4f6e-b49d-04743822e880" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_baeae57e-5e51-4944-8e92-061220b3c1ec" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateContractMember_7a6e37a8-70d8-46b5-9f10-9dfdc5a69faa" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InterestRateContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_baeae57e-5e51-4944-8e92-061220b3c1ec" xlink:to="loc_us-gaap_InterestRateContractMember_7a6e37a8-70d8-46b5-9f10-9dfdc5a69faa" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/AccountingforDerivativeInstrumentsandHedgingActivitiesPretaxEffectsofEconomicHedgesnotDesignatedasCashFlowHedgesDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#AccountingforDerivativeInstrumentsandHedgingActivitiesPretaxEffectsofEconomicHedgesnotDesignatedasCashFlowHedgesDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/AccountingforDerivativeInstrumentsandHedgingActivitiesPretaxEffectsofEconomicHedgesnotDesignatedasCashFlowHedgesDetails" xlink:type="extended" id="if7c5faed8aa741abb4f573940a83ecf7_AccountingforDerivativeInstrumentsandHedgingActivitiesPretaxEffectsofEconomicHedgesnotDesignatedasCashFlowHedgesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLineItems_e5e4d994-db5b-495e-ada1-488670ec9a1b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_UnrealizedMarkToMarketResultsAbstract_8edcfbda-aa61-4daf-9be1-fb6c79878132" xlink:href="nrg-20201231.xsd#nrg_UnrealizedMarkToMarketResultsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_e5e4d994-db5b-495e-ada1-488670ec9a1b" xlink:to="loc_nrg_UnrealizedMarkToMarketResultsAbstract_8edcfbda-aa61-4daf-9be1-fb6c79878132" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_ReversalPreviouslyRecognizedUnrealizedGainsLossesSettledPositionsEconomicHedges_cc93a377-674c-4d50-816d-1e3016076828" xlink:href="nrg-20201231.xsd#nrg_ReversalPreviouslyRecognizedUnrealizedGainsLossesSettledPositionsEconomicHedges"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_UnrealizedMarkToMarketResultsAbstract_8edcfbda-aa61-4daf-9be1-fb6c79878132" xlink:to="loc_nrg_ReversalPreviouslyRecognizedUnrealizedGainsLossesSettledPositionsEconomicHedges_cc93a377-674c-4d50-816d-1e3016076828" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_ReversalPreviouslyRecognizedUnrealizedGainsLossesAcquiredasPartofAcquisitionEconomicHedges_8083a6f2-177c-4ec7-9314-6ac23f1304a3" xlink:href="nrg-20201231.xsd#nrg_ReversalPreviouslyRecognizedUnrealizedGainsLossesAcquiredasPartofAcquisitionEconomicHedges"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_UnrealizedMarkToMarketResultsAbstract_8edcfbda-aa61-4daf-9be1-fb6c79878132" xlink:to="loc_nrg_ReversalPreviouslyRecognizedUnrealizedGainsLossesAcquiredasPartofAcquisitionEconomicHedges_8083a6f2-177c-4ec7-9314-6ac23f1304a3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet_d9ad04b6-9ca5-4bb6-b26a-93a128967d71" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_UnrealizedMarkToMarketResultsAbstract_8edcfbda-aa61-4daf-9be1-fb6c79878132" xlink:to="loc_us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet_d9ad04b6-9ca5-4bb6-b26a-93a128967d71" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_UnrealizedGainLossOnDerivativesMarkToMarketEconomicHedgingActivities_6878d150-3254-4076-a3b2-80748136c806" xlink:href="nrg-20201231.xsd#nrg_UnrealizedGainLossOnDerivativesMarkToMarketEconomicHedgingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_UnrealizedMarkToMarketResultsAbstract_8edcfbda-aa61-4daf-9be1-fb6c79878132" xlink:to="loc_nrg_UnrealizedGainLossOnDerivativesMarkToMarketEconomicHedgingActivities_6878d150-3254-4076-a3b2-80748136c806" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_ReversalPreviouslyUnrecognizedUnrealizedGainsLossesSettledPositionsTradingActivity_cdd74589-cd5e-49e2-8387-a9716d169fed" xlink:href="nrg-20201231.xsd#nrg_ReversalPreviouslyUnrecognizedUnrealizedGainsLossesSettledPositionsTradingActivity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_UnrealizedMarkToMarketResultsAbstract_8edcfbda-aa61-4daf-9be1-fb6c79878132" xlink:to="loc_nrg_ReversalPreviouslyUnrecognizedUnrealizedGainsLossesSettledPositionsTradingActivity_cdd74589-cd5e-49e2-8387-a9716d169fed" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_DerivativeUnrealizedGainsOnOpenPositionsRelatedToTradingActivityNet_70dd5ae3-d13e-4ec9-91c2-4fd78d5fef29" xlink:href="nrg-20201231.xsd#nrg_DerivativeUnrealizedGainsOnOpenPositionsRelatedToTradingActivityNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_UnrealizedMarkToMarketResultsAbstract_8edcfbda-aa61-4daf-9be1-fb6c79878132" xlink:to="loc_nrg_DerivativeUnrealizedGainsOnOpenPositionsRelatedToTradingActivityNet_70dd5ae3-d13e-4ec9-91c2-4fd78d5fef29" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_UnrealizedGainLossonDerivativesMarkToMarketTradingActivities_7fafc07d-58b8-4fe0-93f8-c05f080a3cef" xlink:href="nrg-20201231.xsd#nrg_UnrealizedGainLossonDerivativesMarkToMarketTradingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_UnrealizedMarkToMarketResultsAbstract_8edcfbda-aa61-4daf-9be1-fb6c79878132" xlink:to="loc_nrg_UnrealizedGainLossonDerivativesMarkToMarketTradingActivities_7fafc07d-58b8-4fe0-93f8-c05f080a3cef" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnrealizedGainLossOnDerivatives_d444083b-89e0-4b99-9f86-66e9e8e0dfa3" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_UnrealizedGainLossOnDerivatives"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_UnrealizedMarkToMarketResultsAbstract_8edcfbda-aa61-4daf-9be1-fb6c79878132" xlink:to="loc_us-gaap_UnrealizedGainLossOnDerivatives_d444083b-89e0-4b99-9f86-66e9e8e0dfa3" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_CreditRiskRelatedContingentFeaturesAbstract_6825cdd8-3d04-4bce-8ff2-9e82114a2670" xlink:href="nrg-20201231.xsd#nrg_CreditRiskRelatedContingentFeaturesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_e5e4d994-db5b-495e-ada1-488670ec9a1b" xlink:to="loc_nrg_CreditRiskRelatedContingentFeaturesAbstract_6825cdd8-3d04-4bce-8ff2-9e82114a2670" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CollateralAlreadyPostedAggregateFairValue_d4bf063b-0a53-47da-a811-8f987cde89c8" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CollateralAlreadyPostedAggregateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_CreditRiskRelatedContingentFeaturesAbstract_6825cdd8-3d04-4bce-8ff2-9e82114a2670" xlink:to="loc_us-gaap_CollateralAlreadyPostedAggregateFairValue_d4bf063b-0a53-47da-a811-8f987cde89c8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeNetLiabilityPositionAggregateFairValue_ed9da7c3-f740-4654-8469-e0ed2f61fe68" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeNetLiabilityPositionAggregateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_CreditRiskRelatedContingentFeaturesAbstract_6825cdd8-3d04-4bce-8ff2-9e82114a2670" xlink:to="loc_us-gaap_DerivativeNetLiabilityPositionAggregateFairValue_ed9da7c3-f740-4654-8469-e0ed2f61fe68" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalCollateralAggregateFairValue_0b70c3d4-9996-4b53-9470-a689efa1c248" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AdditionalCollateralAggregateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_CreditRiskRelatedContingentFeaturesAbstract_6825cdd8-3d04-4bce-8ff2-9e82114a2670" xlink:to="loc_us-gaap_AdditionalCollateralAggregateFairValue_0b70c3d4-9996-4b53-9470-a689efa1c248" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeTable_c746e8c9-eb0f-4a35-bf6c-8e9c4feb8eda" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeLineItems_e5e4d994-db5b-495e-ada1-488670ec9a1b" xlink:to="loc_us-gaap_DerivativeTable_c746e8c9-eb0f-4a35-bf6c-8e9c4feb8eda" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_9e8d68ee-1397-42f8-b9b5-16aa04e707f9" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_c746e8c9-eb0f-4a35-bf6c-8e9c4feb8eda" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_9e8d68ee-1397-42f8-b9b5-16aa04e707f9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_9e8d68ee-1397-42f8-b9b5-16aa04e707f9_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_9e8d68ee-1397-42f8-b9b5-16aa04e707f9" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_9e8d68ee-1397-42f8-b9b5-16aa04e707f9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_d9f935d9-b509-4153-a5f7-8419d8a24f91" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_9e8d68ee-1397-42f8-b9b5-16aa04e707f9" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_d9f935d9-b509-4153-a5f7-8419d8a24f91" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommodityContractMember_f7805a9f-19ea-4faa-a701-50c467dd566e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommodityContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_d9f935d9-b509-4153-a5f7-8419d8a24f91" xlink:to="loc_us-gaap_CommodityContractMember_f7805a9f-19ea-4faa-a701-50c467dd566e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateContractMember_a0059725-ede9-45d3-82b6-0053b13038c6" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InterestRateContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_d9f935d9-b509-4153-a5f7-8419d8a24f91" xlink:to="loc_us-gaap_InterestRateContractMember_a0059725-ede9-45d3-82b6-0053b13038c6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_dc3c39a4-3348-4f92-bc55-9ed4e3c42aa8" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeStatementLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_c746e8c9-eb0f-4a35-bf6c-8e9c4feb8eda" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_dc3c39a4-3348-4f92-bc55-9ed4e3c42aa8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_dc3c39a4-3348-4f92-bc55-9ed4e3c42aa8_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_dc3c39a4-3348-4f92-bc55-9ed4e3c42aa8" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_dc3c39a4-3348-4f92-bc55-9ed4e3c42aa8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_b58b8090-95a6-42f5-8fbf-2e9379fd843c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_dc3c39a4-3348-4f92-bc55-9ed4e3c42aa8" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_b58b8090-95a6-42f5-8fbf-2e9379fd843c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SalesMember_44d89001-86cc-476e-823b-6ab9ad3ff37d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SalesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_b58b8090-95a6-42f5-8fbf-2e9379fd843c" xlink:to="loc_us-gaap_SalesMember_44d89001-86cc-476e-823b-6ab9ad3ff37d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfSalesMember_9bfe37f6-238c-4a10-a8ad-7b4a67116e8a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CostOfSalesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_b58b8090-95a6-42f5-8fbf-2e9379fd843c" xlink:to="loc_us-gaap_CostOfSalesMember_9bfe37f6-238c-4a10-a8ad-7b4a67116e8a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditDerivativesByContractTypeAxis_fc8d906d-4874-4a8a-8944-16f4d7433a87" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CreditDerivativesByContractTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_c746e8c9-eb0f-4a35-bf6c-8e9c4feb8eda" xlink:to="loc_us-gaap_CreditDerivativesByContractTypeAxis_fc8d906d-4874-4a8a-8944-16f4d7433a87" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditDerivativesContractTypeDomain_fc8d906d-4874-4a8a-8944-16f4d7433a87_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CreditDerivativesContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditDerivativesByContractTypeAxis_fc8d906d-4874-4a8a-8944-16f4d7433a87" xlink:to="loc_us-gaap_CreditDerivativesContractTypeDomain_fc8d906d-4874-4a8a-8944-16f4d7433a87_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditDerivativesContractTypeDomain_7c60780d-23c1-4477-a51e-2afd504cbfeb" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CreditDerivativesContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditDerivativesByContractTypeAxis_fc8d906d-4874-4a8a-8944-16f4d7433a87" xlink:to="loc_us-gaap_CreditDerivativesContractTypeDomain_7c60780d-23c1-4477-a51e-2afd504cbfeb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_AdequateAssuranceClausesMember_cde2049c-3df4-45a1-99eb-2cf5ca601d9d" xlink:href="nrg-20201231.xsd#nrg_AdequateAssuranceClausesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditDerivativesContractTypeDomain_7c60780d-23c1-4477-a51e-2afd504cbfeb" xlink:to="loc_nrg_AdequateAssuranceClausesMember_cde2049c-3df4-45a1-99eb-2cf5ca601d9d" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/NuclearDecommissioningTrustFund" xlink:type="simple" xlink:href="nrg-20201231.xsd#NuclearDecommissioningTrustFund"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/NuclearDecommissioningTrustFund" xlink:type="extended" id="i62c233c18da04059b13849f186b0ed2e_NuclearDecommissioningTrustFund"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/NuclearDecommissioningTrustFundTables" xlink:type="simple" xlink:href="nrg-20201231.xsd#NuclearDecommissioningTrustFundTables"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/NuclearDecommissioningTrustFundTables" xlink:type="extended" id="i340344a8a4494f5ca858522a183ca409_NuclearDecommissioningTrustFundTables"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/NuclearDecommissioningTrustFundSummaryofAggregateFairValuesandRealizedGainsandLossesDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#NuclearDecommissioningTrustFundSummaryofAggregateFairValuesandRealizedGainsandLossesDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/NuclearDecommissioningTrustFundSummaryofAggregateFairValuesandRealizedGainsandLossesDetails" xlink:type="extended" id="iac284434d2ad4a82b64dce76882cf92c_NuclearDecommissioningTrustFundSummaryofAggregateFairValuesandRealizedGainsandLossesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_89c75f79-9ab3-4833-9ba8-7fb6795c9086" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_JointlyOwnedUtilityPlantProportionateOwnershipShare_ed73c625-e10d-4bfc-a41d-0b9ba14a1626" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_JointlyOwnedUtilityPlantProportionateOwnershipShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_89c75f79-9ab3-4833-9ba8-7fb6795c9086" xlink:to="loc_us-gaap_JointlyOwnedUtilityPlantProportionateOwnershipShare_ed73c625-e10d-4bfc-a41d-0b9ba14a1626" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DecommissioningTrustAssetsAmount_5edd0bac-d153-4fdf-8dbf-970e211d34ef" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DecommissioningTrustAssetsAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_89c75f79-9ab3-4833-9ba8-7fb6795c9086" xlink:to="loc_us-gaap_DecommissioningTrustAssetsAmount_5edd0bac-d153-4fdf-8dbf-970e211d34ef" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_DecommissioningFundInvestmentsUnrealizedGains_64f7d7cc-28a7-4b7c-ae09-e7835d55902c" xlink:href="nrg-20201231.xsd#nrg_DecommissioningFundInvestmentsUnrealizedGains"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_89c75f79-9ab3-4833-9ba8-7fb6795c9086" xlink:to="loc_nrg_DecommissioningFundInvestmentsUnrealizedGains_64f7d7cc-28a7-4b7c-ae09-e7835d55902c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_DecommissioningFundInvestmentsUnrealizedLoss_51f55839-4ef1-45ac-b6d1-9fd458a8bada" xlink:href="nrg-20201231.xsd#nrg_DecommissioningFundInvestmentsUnrealizedLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_89c75f79-9ab3-4833-9ba8-7fb6795c9086" xlink:to="loc_nrg_DecommissioningFundInvestmentsUnrealizedLoss_51f55839-4ef1-45ac-b6d1-9fd458a8bada" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_DecommissioningTrustAssetsWeightedAverageMaturityPeriod_5427b002-1aca-4dda-856f-44ddbcb0254e" xlink:href="nrg-20201231.xsd#nrg_DecommissioningTrustAssetsWeightedAverageMaturityPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_89c75f79-9ab3-4833-9ba8-7fb6795c9086" xlink:to="loc_nrg_DecommissioningTrustAssetsWeightedAverageMaturityPeriod_5427b002-1aca-4dda-856f-44ddbcb0254e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_7f64594e-2ee6-401a-8192-29ed132fc0a7" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtSecuritiesAvailableForSaleTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_89c75f79-9ab3-4833-9ba8-7fb6795c9086" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_7f64594e-2ee6-401a-8192-29ed132fc0a7" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_JointlyOwnedUtilityPlantAxis_2c623f3f-a612-4b1d-8241-3d48603c7d27" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_JointlyOwnedUtilityPlantAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_7f64594e-2ee6-401a-8192-29ed132fc0a7" xlink:to="loc_us-gaap_JointlyOwnedUtilityPlantAxis_2c623f3f-a612-4b1d-8241-3d48603c7d27" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_JointlyOwnedUtilityPlantDomain_2c623f3f-a612-4b1d-8241-3d48603c7d27_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_JointlyOwnedUtilityPlantDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_JointlyOwnedUtilityPlantAxis_2c623f3f-a612-4b1d-8241-3d48603c7d27" xlink:to="loc_us-gaap_JointlyOwnedUtilityPlantDomain_2c623f3f-a612-4b1d-8241-3d48603c7d27_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_JointlyOwnedUtilityPlantDomain_2a40b8d7-26cb-4984-b88e-f3c311d9d33c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_JointlyOwnedUtilityPlantDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_JointlyOwnedUtilityPlantAxis_2c623f3f-a612-4b1d-8241-3d48603c7d27" xlink:to="loc_us-gaap_JointlyOwnedUtilityPlantDomain_2a40b8d7-26cb-4984-b88e-f3c311d9d33c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_SouthTexasProjectUnits1And2Member_5fce29e9-01fe-4693-aeba-6e2d95def091" xlink:href="nrg-20201231.xsd#nrg_SouthTexasProjectUnits1And2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_JointlyOwnedUtilityPlantDomain_2a40b8d7-26cb-4984-b88e-f3c311d9d33c" xlink:to="loc_nrg_SouthTexasProjectUnits1And2Member_5fce29e9-01fe-4693-aeba-6e2d95def091" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_58e0599d-312b-4706-8299-48926d93c119" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_7f64594e-2ee6-401a-8192-29ed132fc0a7" xlink:to="loc_us-gaap_FinancialInstrumentAxis_58e0599d-312b-4706-8299-48926d93c119" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_58e0599d-312b-4706-8299-48926d93c119_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_58e0599d-312b-4706-8299-48926d93c119" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_58e0599d-312b-4706-8299-48926d93c119_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_8e47b732-6e8b-4981-b3e6-9b87202a1b42" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_58e0599d-312b-4706-8299-48926d93c119" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_8e47b732-6e8b-4981-b3e6-9b87202a1b42" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsMember_44a80e7c-09b3-41fb-9830-45b0b2d08cbb" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CashAndCashEquivalentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_8e47b732-6e8b-4981-b3e6-9b87202a1b42" xlink:to="loc_us-gaap_CashAndCashEquivalentsMember_44a80e7c-09b3-41fb-9830-45b0b2d08cbb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember_8bf2f313-8365-4c9b-8646-0252ae2f2500" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_8e47b732-6e8b-4981-b3e6-9b87202a1b42" xlink:to="loc_us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember_8bf2f313-8365-4c9b-8646-0252ae2f2500" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember_66ed72fb-439f-4ce0-a907-e2a7ebe21bb6" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_8e47b732-6e8b-4981-b3e6-9b87202a1b42" xlink:to="loc_us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember_66ed72fb-439f-4ce0-a907-e2a7ebe21bb6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialMortgageBackedSecuritiesMember_b7013451-2cbf-4375-9191-3ee3e0277d5a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommercialMortgageBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_8e47b732-6e8b-4981-b3e6-9b87202a1b42" xlink:to="loc_us-gaap_CommercialMortgageBackedSecuritiesMember_b7013451-2cbf-4375-9191-3ee3e0277d5a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateDebtSecuritiesMember_f08b8395-8822-4c16-a052-6ed2796869eb" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CorporateDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_8e47b732-6e8b-4981-b3e6-9b87202a1b42" xlink:to="loc_us-gaap_CorporateDebtSecuritiesMember_f08b8395-8822-4c16-a052-6ed2796869eb" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesMember_e4a03318-f1b8-4be4-9099-864d667556e5" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquitySecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_8e47b732-6e8b-4981-b3e6-9b87202a1b42" xlink:to="loc_us-gaap_EquitySecuritiesMember_e4a03318-f1b8-4be4-9099-864d667556e5" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignGovernmentDebtSecuritiesMember_1045fb1e-fba2-4243-849c-76928ac3279d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ForeignGovernmentDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_8e47b732-6e8b-4981-b3e6-9b87202a1b42" xlink:to="loc_us-gaap_ForeignGovernmentDebtSecuritiesMember_1045fb1e-fba2-4243-849c-76928ac3279d" xlink:type="arc" order="6"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/NuclearDecommissioningTrustFundSummaryofProceedsfromSaleofAvailableforsaleSecuritiesDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#NuclearDecommissioningTrustFundSummaryofProceedsfromSaleofAvailableforsaleSecuritiesDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/NuclearDecommissioningTrustFundSummaryofProceedsfromSaleofAvailableforsaleSecuritiesDetails" xlink:type="extended" id="i9d661c97012e4d04bc23795cd5c6d0d2_NuclearDecommissioningTrustFundSummaryofProceedsfromSaleofAvailableforsaleSecuritiesDetails"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/Inventory" xlink:type="simple" xlink:href="nrg-20201231.xsd#Inventory"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/Inventory" xlink:type="extended" id="i6b65c9861f4f407ba6aeee7804958bb7_Inventory"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/InventoryTables" xlink:type="simple" xlink:href="nrg-20201231.xsd#InventoryTables"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/InventoryTables" xlink:type="extended" id="i28cb44a88cf641669ee29e24d56f7150_InventoryTables"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/InventoryDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#InventoryDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/InventoryDetails" xlink:type="extended" id="i807f65ecdef6433892e75806161e56e7_InventoryDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryLineItems_2fcf9af5-32c8-4443-878f-ed9dde3c177b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InventoryLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_OilInventoryLowerOfCostOrMarketAdjustment_a21b81e8-1ba6-4c5d-823e-aefe09a5add8" xlink:href="nrg-20201231.xsd#nrg_OilInventoryLowerOfCostOrMarketAdjustment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InventoryLineItems_2fcf9af5-32c8-4443-878f-ed9dde3c177b" xlink:to="loc_nrg_OilInventoryLowerOfCostOrMarketAdjustment_a21b81e8-1ba6-4c5d-823e-aefe09a5add8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryCurrentTable_f52efcab-8a6d-4d05-99c8-ca0f4cc782ed" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InventoryCurrentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_InventoryLineItems_2fcf9af5-32c8-4443-878f-ed9dde3c177b" xlink:to="loc_us-gaap_InventoryCurrentTable_f52efcab-8a6d-4d05-99c8-ca0f4cc782ed" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PublicUtilitiesInventoryAxis_dde3bacc-4157-4d82-b624-1e53516a3544" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PublicUtilitiesInventoryAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_InventoryCurrentTable_f52efcab-8a6d-4d05-99c8-ca0f4cc782ed" xlink:to="loc_us-gaap_PublicUtilitiesInventoryAxis_dde3bacc-4157-4d82-b624-1e53516a3544" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PublicUtilitiesInventoryTypeDomain_dde3bacc-4157-4d82-b624-1e53516a3544_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PublicUtilitiesInventoryTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PublicUtilitiesInventoryAxis_dde3bacc-4157-4d82-b624-1e53516a3544" xlink:to="loc_us-gaap_PublicUtilitiesInventoryTypeDomain_dde3bacc-4157-4d82-b624-1e53516a3544_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PublicUtilitiesInventoryTypeDomain_256dc701-6bdb-47d6-a20e-cbdb2885f8d7" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PublicUtilitiesInventoryTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PublicUtilitiesInventoryAxis_dde3bacc-4157-4d82-b624-1e53516a3544" xlink:to="loc_us-gaap_PublicUtilitiesInventoryTypeDomain_256dc701-6bdb-47d6-a20e-cbdb2885f8d7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CrudeOilMember_8542e93c-d547-493c-89e4-a1eace2f43a2" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_CrudeOilMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PublicUtilitiesInventoryTypeDomain_256dc701-6bdb-47d6-a20e-cbdb2885f8d7" xlink:to="loc_srt_CrudeOilMember_8542e93c-d547-493c-89e4-a1eace2f43a2" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/PropertyPlantandEquipment" xlink:type="simple" xlink:href="nrg-20201231.xsd#PropertyPlantandEquipment"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/PropertyPlantandEquipment" xlink:type="extended" id="ic4e48d4ce6344163a87b2ff1301dd8e2_PropertyPlantandEquipment"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/PropertyPlantandEquipmentTables" xlink:type="simple" xlink:href="nrg-20201231.xsd#PropertyPlantandEquipmentTables"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/PropertyPlantandEquipmentTables" xlink:type="extended" id="icc947905ce484828a4937ade5ee4f172_PropertyPlantandEquipmentTables"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/PropertyPlantandEquipmentDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#PropertyPlantandEquipmentDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/PropertyPlantandEquipmentDetails" xlink:type="extended" id="iadded1f996de4e5881993f423979e5ed_PropertyPlantandEquipmentDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentLineItems_25790219-9063-4e63-b701-d459c9f403e7" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PropertyPlantAndEquipmentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PublicUtilitiesPropertyPlantAndEquipmentPlantInService_6c15f8e0-52ed-4183-9822-c5a4ab0b7619" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PublicUtilitiesPropertyPlantAndEquipmentPlantInService"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_25790219-9063-4e63-b701-d459c9f403e7" xlink:to="loc_us-gaap_PublicUtilitiesPropertyPlantAndEquipmentPlantInService_6c15f8e0-52ed-4183-9822-c5a4ab0b7619" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PublicUtilitiesPropertyPlantAndEquipmentAccumulatedDepreciation_1179f96e-c61c-4997-aaff-d425ccad13b2" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PublicUtilitiesPropertyPlantAndEquipmentAccumulatedDepreciation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_25790219-9063-4e63-b701-d459c9f403e7" xlink:to="loc_us-gaap_PublicUtilitiesPropertyPlantAndEquipmentAccumulatedDepreciation_1179f96e-c61c-4997-aaff-d425ccad13b2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PublicUtilitiesPropertyPlantAndEquipmentNet_18361911-ddbc-481c-945b-0e1a65cba430" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PublicUtilitiesPropertyPlantAndEquipmentNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_25790219-9063-4e63-b701-d459c9f403e7" xlink:to="loc_us-gaap_PublicUtilitiesPropertyPlantAndEquipmentNet_18361911-ddbc-481c-945b-0e1a65cba430" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentUsefulLife_461231a8-522e-449c-b4bf-e4f54e646101" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PropertyPlantAndEquipmentUsefulLife"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_25790219-9063-4e63-b701-d459c9f403e7" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentUsefulLife_461231a8-522e-449c-b4bf-e4f54e646101" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Depreciation_9c6f36a9-88ed-4651-8d48-47d25db01fbe" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_Depreciation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_25790219-9063-4e63-b701-d459c9f403e7" xlink:to="loc_us-gaap_Depreciation_9c6f36a9-88ed-4651-8d48-47d25db01fbe" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_bf77d13c-ed74-4088-adb6-ec7310e07c3e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfPropertyPlantAndEquipmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_25790219-9063-4e63-b701-d459c9f403e7" xlink:to="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_bf77d13c-ed74-4088-adb6-ec7310e07c3e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_e23f7510-87c3-473a-9556-c13e39435e1d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_bf77d13c-ed74-4088-adb6-ec7310e07c3e" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_e23f7510-87c3-473a-9556-c13e39435e1d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_e23f7510-87c3-473a-9556-c13e39435e1d_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_e23f7510-87c3-473a-9556-c13e39435e1d" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_e23f7510-87c3-473a-9556-c13e39435e1d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_6433649c-bb47-4648-a45d-2d6d1905fac7" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_e23f7510-87c3-473a-9556-c13e39435e1d" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_6433649c-bb47-4648-a45d-2d6d1905fac7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_FacilitiesAndEquipmentMember_9354eed3-a591-4cf7-9e16-b26a79d290f8" xlink:href="nrg-20201231.xsd#nrg_FacilitiesAndEquipmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_6433649c-bb47-4648-a45d-2d6d1905fac7" xlink:to="loc_nrg_FacilitiesAndEquipmentMember_9354eed3-a591-4cf7-9e16-b26a79d290f8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LandAndLandImprovementsMember_25768e11-dd3e-4542-8aa4-b165af07d350" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LandAndLandImprovementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_6433649c-bb47-4648-a45d-2d6d1905fac7" xlink:to="loc_us-gaap_LandAndLandImprovementsMember_25768e11-dd3e-4542-8aa4-b165af07d350" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NuclearFuelMember_423b71d0-a5b0-44b3-b8b0-efdaa7f858ee" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NuclearFuelMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_6433649c-bb47-4648-a45d-2d6d1905fac7" xlink:to="loc_us-gaap_NuclearFuelMember_423b71d0-a5b0-44b3-b8b0-efdaa7f858ee" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OfficeEquipmentMember_3aabd048-fc4a-4be6-89a4-dbd890628764" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OfficeEquipmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_6433649c-bb47-4648-a45d-2d6d1905fac7" xlink:to="loc_us-gaap_OfficeEquipmentMember_3aabd048-fc4a-4be6-89a4-dbd890628764" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConstructionInProgressMember_69735dd4-2172-4789-8522-18ce476d7ed9" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ConstructionInProgressMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_6433649c-bb47-4648-a45d-2d6d1905fac7" xlink:to="loc_us-gaap_ConstructionInProgressMember_69735dd4-2172-4789-8522-18ce476d7ed9" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_17d1fb1c-5084-41db-919a-2f7395b31849" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_bf77d13c-ed74-4088-adb6-ec7310e07c3e" xlink:to="loc_srt_RangeAxis_17d1fb1c-5084-41db-919a-2f7395b31849" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_17d1fb1c-5084-41db-919a-2f7395b31849_default" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_17d1fb1c-5084-41db-919a-2f7395b31849" xlink:to="loc_srt_RangeMember_17d1fb1c-5084-41db-919a-2f7395b31849_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_d8de5acd-33b8-4939-902b-ebd2068cd3fd" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_17d1fb1c-5084-41db-919a-2f7395b31849" xlink:to="loc_srt_RangeMember_d8de5acd-33b8-4939-902b-ebd2068cd3fd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_c072d4f4-1b4c-4068-8144-73123f5cf0d3" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_d8de5acd-33b8-4939-902b-ebd2068cd3fd" xlink:to="loc_srt_MinimumMember_c072d4f4-1b4c-4068-8144-73123f5cf0d3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_d979e86b-42b3-4f84-8765-df4f057211f9" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_d8de5acd-33b8-4939-902b-ebd2068cd3fd" xlink:to="loc_srt_MaximumMember_d979e86b-42b3-4f84-8765-df4f057211f9" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/Leases" xlink:type="simple" xlink:href="nrg-20201231.xsd#Leases"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/Leases" xlink:type="extended" id="i47b2f1137ff7441899ba9a2db2502ea1_Leases"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/LeasesTables" xlink:type="simple" xlink:href="nrg-20201231.xsd#LeasesTables"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/LeasesTables" xlink:type="extended" id="i45517654c76f4d6dbd948fcc37c2f607_LeasesTables"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/LeasesLeaseCostandOtherInformationDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#LeasesLeaseCostandOtherInformationDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/LeasesLeaseCostandOtherInformationDetails" xlink:type="extended" id="i4ef71487d4174137a0b23b3cbda93229_LeasesLeaseCostandOtherInformationDetails"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/LeasesAnnualPaymentsBasedontheMaturitiesofLeasesDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#LeasesAnnualPaymentsBasedontheMaturitiesofLeasesDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/LeasesAnnualPaymentsBasedontheMaturitiesofLeasesDetails" xlink:type="extended" id="ie4dd0166565f4c1f88fb04cdfb159a47_LeasesAnnualPaymentsBasedontheMaturitiesofLeasesDetails"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/AssetImpairments" xlink:type="simple" xlink:href="nrg-20201231.xsd#AssetImpairments"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/AssetImpairments" xlink:type="extended" id="i7ab991723bcd46b99539fba1146bfa17_AssetImpairments"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/AssetImpairmentsDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#AssetImpairmentsDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/AssetImpairmentsDetails" xlink:type="extended" id="i935b0e8b052143f2ac91e587f8c388e3_AssetImpairmentsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ImpairedLongLivedAssetsHeldAndUsedLineItems_0e23be9f-0cfa-42b9-ac2f-3522d95b6664" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ImpairedLongLivedAssetsHeldAndUsedLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentOtherThanTemporaryImpairment_917c0e5f-d8aa-45f5-83ba-be869191d3d7" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityMethodInvestmentOtherThanTemporaryImpairment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ImpairedLongLivedAssetsHeldAndUsedLineItems_0e23be9f-0cfa-42b9-ac2f-3522d95b6664" xlink:to="loc_us-gaap_EquityMethodInvestmentOtherThanTemporaryImpairment_917c0e5f-d8aa-45f5-83ba-be869191d3d7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LettersOfCreditOutstandingAmount_8525eda4-e8ed-4768-8b04-f1682fcc4f2f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LettersOfCreditOutstandingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ImpairedLongLivedAssetsHeldAndUsedLineItems_0e23be9f-0cfa-42b9-ac2f-3522d95b6664" xlink:to="loc_us-gaap_LettersOfCreditOutstandingAmount_8525eda4-e8ed-4768-8b04-f1682fcc4f2f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireEquityMethodInvestments_8cf79546-f7ed-47fe-9177-79c06037c1b6" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PaymentsToAcquireEquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ImpairedLongLivedAssetsHeldAndUsedLineItems_0e23be9f-0cfa-42b9-ac2f-3522d95b6664" xlink:to="loc_us-gaap_PaymentsToAcquireEquityMethodInvestments_8cf79546-f7ed-47fe-9177-79c06037c1b6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GuaranteeObligationsMaximumExposure_a6068432-eb0c-4a41-b26d-30a7456f1a18" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GuaranteeObligationsMaximumExposure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ImpairedLongLivedAssetsHeldAndUsedLineItems_0e23be9f-0cfa-42b9-ac2f-3522d95b6664" xlink:to="loc_us-gaap_GuaranteeObligationsMaximumExposure_a6068432-eb0c-4a41-b26d-30a7456f1a18" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetImpairmentCharges_6410896d-ef13-4efa-bfa6-7c539d0e2c18" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherAssetImpairmentCharges"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ImpairedLongLivedAssetsHeldAndUsedLineItems_0e23be9f-0cfa-42b9-ac2f-3522d95b6664" xlink:to="loc_us-gaap_OtherAssetImpairmentCharges_6410896d-ef13-4efa-bfa6-7c539d0e2c18" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetImpairmentCharges_e175ebae-d7a6-478b-95e5-d4c562cfa2f7" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AssetImpairmentCharges"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ImpairedLongLivedAssetsHeldAndUsedLineItems_0e23be9f-0cfa-42b9-ac2f-3522d95b6664" xlink:to="loc_us-gaap_AssetImpairmentCharges_e175ebae-d7a6-478b-95e5-d4c562cfa2f7" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationConsideration_a9e94cbf-12e9-4c1e-b3c4-25a6cbccd1f7" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DisposalGroupIncludingDiscontinuedOperationConsideration"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ImpairedLongLivedAssetsHeldAndUsedLineItems_0e23be9f-0cfa-42b9-ac2f-3522d95b6664" xlink:to="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationConsideration_a9e94cbf-12e9-4c1e-b3c4-25a6cbccd1f7" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_48ee6122-b9a5-473c-b8fb-e7455da02440" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityMethodInvestmentOwnershipPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ImpairedLongLivedAssetsHeldAndUsedLineItems_0e23be9f-0cfa-42b9-ac2f-3522d95b6664" xlink:to="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_48ee6122-b9a5-473c-b8fb-e7455da02440" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestments_16e0adc9-2f3f-4058-8146-7344dd1373f8" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ImpairedLongLivedAssetsHeldAndUsedLineItems_0e23be9f-0cfa-42b9-ac2f-3522d95b6664" xlink:to="loc_us-gaap_EquityMethodInvestments_16e0adc9-2f3f-4058-8146-7344dd1373f8" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ImpairmentOfInvestments_48501156-9a01-48f4-88e6-a457b3f7c9a3" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ImpairmentOfInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ImpairedLongLivedAssetsHeldAndUsedLineItems_0e23be9f-0cfa-42b9-ac2f-3522d95b6664" xlink:to="loc_us-gaap_ImpairmentOfInvestments_48501156-9a01-48f4-88e6-a457b3f7c9a3" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfImpairedLongLivedAssetsHeldAndUsedTable_6747895a-bfac-443b-a278-9e78aa3d0639" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfImpairedLongLivedAssetsHeldAndUsedTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ImpairedLongLivedAssetsHeldAndUsedLineItems_0e23be9f-0cfa-42b9-ac2f-3522d95b6664" xlink:to="loc_us-gaap_ScheduleOfImpairedLongLivedAssetsHeldAndUsedTable_6747895a-bfac-443b-a278-9e78aa3d0639" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_1df197f2-259e-4887-98ce-69d91c42a522" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfImpairedLongLivedAssetsHeldAndUsedTable_6747895a-bfac-443b-a278-9e78aa3d0639" xlink:to="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_1df197f2-259e-4887-98ce-69d91c42a522" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_1df197f2-259e-4887-98ce-69d91c42a522_default" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_1df197f2-259e-4887-98ce-69d91c42a522" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_1df197f2-259e-4887-98ce-69d91c42a522_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_c3f5d5be-6efe-452e-8821-2ca817c002d9" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_1df197f2-259e-4887-98ce-69d91c42a522" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_c3f5d5be-6efe-452e-8821-2ca817c002d9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_CottonwoodMember_181ceefb-a026-4b56-a8bc-46f9e105336b" xlink:href="nrg-20201231.xsd#nrg_CottonwoodMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_c3f5d5be-6efe-452e-8821-2ca817c002d9" xlink:to="loc_nrg_CottonwoodMember_181ceefb-a026-4b56-a8bc-46f9e105336b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_HomeSolarMember_19f87c0c-1787-4fdd-b205-04de115bd79b" xlink:href="nrg-20201231.xsd#nrg_HomeSolarMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_c3f5d5be-6efe-452e-8821-2ca817c002d9" xlink:to="loc_nrg_HomeSolarMember_19f87c0c-1787-4fdd-b205-04de115bd79b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_PetraNovaParishHoldingsMember_36a299ca-ad31-4852-8996-2c5177e24e95" xlink:href="nrg-20201231.xsd#nrg_PetraNovaParishHoldingsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_c3f5d5be-6efe-452e-8821-2ca817c002d9" xlink:to="loc_nrg_PetraNovaParishHoldingsMember_36a299ca-ad31-4852-8996-2c5177e24e95" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_KeystoneMember_10c909a9-3f02-4af2-93b4-9ee4362cfe75" xlink:href="nrg-20201231.xsd#nrg_KeystoneMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_c3f5d5be-6efe-452e-8821-2ca817c002d9" xlink:to="loc_nrg_KeystoneMember_10c909a9-3f02-4af2-93b4-9ee4362cfe75" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_ConemaughMember_19025000-b722-4414-af84-77283e67fea8" xlink:href="nrg-20201231.xsd#nrg_ConemaughMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_c3f5d5be-6efe-452e-8821-2ca817c002d9" xlink:to="loc_nrg_ConemaughMember_19025000-b722-4414-af84-77283e67fea8" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_DunkirkMember_0825f039-a300-49ce-b500-34b74f897c1a" xlink:href="nrg-20201231.xsd#nrg_DunkirkMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_c3f5d5be-6efe-452e-8821-2ca817c002d9" xlink:to="loc_nrg_DunkirkMember_0825f039-a300-49ce-b500-34b74f897c1a" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_OtherEquityMethodInvestmentsMember_0a2228f3-1d5d-4484-9597-69f81aa12cb9" xlink:href="nrg-20201231.xsd#nrg_OtherEquityMethodInvestmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_c3f5d5be-6efe-452e-8821-2ca817c002d9" xlink:to="loc_nrg_OtherEquityMethodInvestmentsMember_0a2228f3-1d5d-4484-9597-69f81aa12cb9" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationAxis_cb018228-4543-4dd6-b48e-26be1adb7152" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DisposalGroupClassificationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfImpairedLongLivedAssetsHeldAndUsedTable_6747895a-bfac-443b-a278-9e78aa3d0639" xlink:to="loc_us-gaap_DisposalGroupClassificationAxis_cb018228-4543-4dd6-b48e-26be1adb7152" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationDomain_cb018228-4543-4dd6-b48e-26be1adb7152_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DisposalGroupClassificationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DisposalGroupClassificationAxis_cb018228-4543-4dd6-b48e-26be1adb7152" xlink:to="loc_us-gaap_DisposalGroupClassificationDomain_cb018228-4543-4dd6-b48e-26be1adb7152_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationDomain_5f8f064b-b2a5-4582-b398-89674a2608e9" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DisposalGroupClassificationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DisposalGroupClassificationAxis_cb018228-4543-4dd6-b48e-26be1adb7152" xlink:to="loc_us-gaap_DisposalGroupClassificationDomain_5f8f064b-b2a5-4582-b398-89674a2608e9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupHeldforsaleNotDiscontinuedOperationsMember_95241871-d749-4651-9207-f349b8642ae2" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DisposalGroupHeldforsaleNotDiscontinuedOperationsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupClassificationDomain_5f8f064b-b2a5-4582-b398-89674a2608e9" xlink:to="loc_us-gaap_DisposalGroupHeldforsaleNotDiscontinuedOperationsMember_95241871-d749-4651-9207-f349b8642ae2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_4a9c5318-82c4-46dd-b65a-9227f2ba1a3b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfImpairedLongLivedAssetsHeldAndUsedTable_6747895a-bfac-443b-a278-9e78aa3d0639" xlink:to="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_4a9c5318-82c4-46dd-b65a-9227f2ba1a3b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_4a9c5318-82c4-46dd-b65a-9227f2ba1a3b_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_4a9c5318-82c4-46dd-b65a-9227f2ba1a3b" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_4a9c5318-82c4-46dd-b65a-9227f2ba1a3b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_9bb8303b-21cd-4069-894c-089c81a519fc" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_4a9c5318-82c4-46dd-b65a-9227f2ba1a3b" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_9bb8303b-21cd-4069-894c-089c81a519fc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_NRGSolarGuamLLCMember_b390aa0b-042a-4bfd-b6dd-9d13bec4e687" xlink:href="nrg-20201231.xsd#nrg_NRGSolarGuamLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_9bb8303b-21cd-4069-894c-089c81a519fc" xlink:to="loc_nrg_NRGSolarGuamLLCMember_b390aa0b-042a-4bfd-b6dd-9d13bec4e687" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_bd2073c6-9385-49d8-8c0d-e634a6c54e0b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfImpairedLongLivedAssetsHeldAndUsedTable_6747895a-bfac-443b-a278-9e78aa3d0639" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_bd2073c6-9385-49d8-8c0d-e634a6c54e0b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_bd2073c6-9385-49d8-8c0d-e634a6c54e0b_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_bd2073c6-9385-49d8-8c0d-e634a6c54e0b" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_bd2073c6-9385-49d8-8c0d-e634a6c54e0b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_4b37125c-8c38-4eaa-bbc7-eaa32f0a1b4f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_bd2073c6-9385-49d8-8c0d-e634a6c54e0b" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_4b37125c-8c38-4eaa-bbc7-eaa32f0a1b4f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConstructionInProgressMember_49281877-e5d7-4536-b26e-3d1e0cb59666" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ConstructionInProgressMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_4b37125c-8c38-4eaa-bbc7-eaa32f0a1b4f" xlink:to="loc_us-gaap_ConstructionInProgressMember_49281877-e5d7-4536-b26e-3d1e0cb59666" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_aeadecea-a579-46c4-868a-10aac3507614" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfImpairedLongLivedAssetsHeldAndUsedTable_6747895a-bfac-443b-a278-9e78aa3d0639" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_aeadecea-a579-46c4-868a-10aac3507614" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_aeadecea-a579-46c4-868a-10aac3507614_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_aeadecea-a579-46c4-868a-10aac3507614" xlink:to="loc_us-gaap_SegmentDomain_aeadecea-a579-46c4-868a-10aac3507614_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_ab7a7f76-9ae0-418d-a575-1582d7e155f5" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_aeadecea-a579-46c4-868a-10aac3507614" xlink:to="loc_us-gaap_SegmentDomain_ab7a7f76-9ae0-418d-a575-1582d7e155f5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_EastSegmentMember_3dcff36f-5226-4a0d-8176-c10120ad9cf5" xlink:href="nrg-20201231.xsd#nrg_EastSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_ab7a7f76-9ae0-418d-a575-1582d7e155f5" xlink:to="loc_nrg_EastSegmentMember_3dcff36f-5226-4a0d-8176-c10120ad9cf5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_WestAndOtherSegmentMember_5a3edf2e-3e48-4b66-8670-f92db18bc947" xlink:href="nrg-20201231.xsd#nrg_WestAndOtherSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_ab7a7f76-9ae0-418d-a575-1582d7e155f5" xlink:to="loc_nrg_WestAndOtherSegmentMember_5a3edf2e-3e48-4b66-8670-f92db18bc947" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_TexasSegmentMember_0e2a42c5-7364-4e97-9717-d5227059f296" xlink:href="nrg-20201231.xsd#nrg_TexasSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_ab7a7f76-9ae0-418d-a575-1582d7e155f5" xlink:to="loc_nrg_TexasSegmentMember_0e2a42c5-7364-4e97-9717-d5227059f296" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis_35bbe547-94b0-42e0-aa8b-67d7aefb5329" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfImpairedLongLivedAssetsHeldAndUsedTable_6747895a-bfac-443b-a278-9e78aa3d0639" xlink:to="loc_us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis_35bbe547-94b0-42e0-aa8b-67d7aefb5329" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ImpairedLongLivedAssetsHeldAndUsedAssetNameDomain_35bbe547-94b0-42e0-aa8b-67d7aefb5329_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ImpairedLongLivedAssetsHeldAndUsedAssetNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis_35bbe547-94b0-42e0-aa8b-67d7aefb5329" xlink:to="loc_us-gaap_ImpairedLongLivedAssetsHeldAndUsedAssetNameDomain_35bbe547-94b0-42e0-aa8b-67d7aefb5329_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ImpairedLongLivedAssetsHeldAndUsedAssetNameDomain_bf35a2e4-715d-4d00-bd2a-94e90cb2e2ad" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ImpairedLongLivedAssetsHeldAndUsedAssetNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis_35bbe547-94b0-42e0-aa8b-67d7aefb5329" xlink:to="loc_us-gaap_ImpairedLongLivedAssetsHeldAndUsedAssetNameDomain_bf35a2e4-715d-4d00-bd2a-94e90cb2e2ad" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_EmissionAllowancesMember_b939b1ed-342c-4ded-97fc-2d51e7f7c87d" xlink:href="nrg-20201231.xsd#nrg_EmissionAllowancesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ImpairedLongLivedAssetsHeldAndUsedAssetNameDomain_bf35a2e4-715d-4d00-bd2a-94e90cb2e2ad" xlink:to="loc_nrg_EmissionAllowancesMember_b939b1ed-342c-4ded-97fc-2d51e7f7c87d" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/GoodwillandOtherIntangibles" xlink:type="simple" xlink:href="nrg-20201231.xsd#GoodwillandOtherIntangibles"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/GoodwillandOtherIntangibles" xlink:type="extended" id="i9c318bafd2824b7ba68810a826b6d691_GoodwillandOtherIntangibles"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/GoodwillandOtherIntangiblesTables" xlink:type="simple" xlink:href="nrg-20201231.xsd#GoodwillandOtherIntangiblesTables"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/GoodwillandOtherIntangiblesTables" xlink:type="extended" id="idb96b69ea411489f86c9f20ea8cf512e_GoodwillandOtherIntangiblesTables"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/GoodwillandOtherIntangiblesNarrativeDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#GoodwillandOtherIntangiblesNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/GoodwillandOtherIntangiblesNarrativeDetails" xlink:type="extended" id="i72652ad193ca4d36b2cc7055190a28a1_GoodwillandOtherIntangiblesNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_472c9837-5c67-48fd-ad62-6e16340e5b83" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_151d786a-4c0e-47e4-9036-11554e262c4b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_Goodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_472c9837-5c67-48fd-ad62-6e16340e5b83" xlink:to="loc_us-gaap_Goodwill_151d786a-4c0e-47e4-9036-11554e262c4b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_OtherAssetsNoncurrentEmissionAllowances_f585107b-a379-4ed9-bfa6-5261eacbf306" xlink:href="nrg-20201231.xsd#nrg_OtherAssetsNoncurrentEmissionAllowances"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_472c9837-5c67-48fd-ad62-6e16340e5b83" xlink:to="loc_nrg_OtherAssetsNoncurrentEmissionAllowances_f585107b-a379-4ed9-bfa6-5261eacbf306" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_8833a117-7841-4419-ba90-1f1ad5e61abe" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_472c9837-5c67-48fd-ad62-6e16340e5b83" xlink:to="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_8833a117-7841-4419-ba90-1f1ad5e61abe" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_b4c0a9db-0fab-4dba-95ae-ea490710f771" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_8833a117-7841-4419-ba90-1f1ad5e61abe" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_b4c0a9db-0fab-4dba-95ae-ea490710f771" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_b4c0a9db-0fab-4dba-95ae-ea490710f771_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_b4c0a9db-0fab-4dba-95ae-ea490710f771" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_b4c0a9db-0fab-4dba-95ae-ea490710f771_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_f55d5364-9488-4a7c-90fe-6914a0909eee" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_b4c0a9db-0fab-4dba-95ae-ea490710f771" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_f55d5364-9488-4a7c-90fe-6914a0909eee" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_MidwestGenerationMember_0223ae19-50d2-4b7e-9f9d-79555e762ed6" xlink:href="nrg-20201231.xsd#nrg_MidwestGenerationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_f55d5364-9488-4a7c-90fe-6914a0909eee" xlink:to="loc_nrg_MidwestGenerationMember_0223ae19-50d2-4b7e-9f9d-79555e762ed6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_RetailBusinessAcquisitionsMember_23fdbe5d-d8d9-4271-8982-fc89728a9138" xlink:href="nrg-20201231.xsd#nrg_RetailBusinessAcquisitionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_f55d5364-9488-4a7c-90fe-6914a0909eee" xlink:to="loc_nrg_RetailBusinessAcquisitionsMember_23fdbe5d-d8d9-4271-8982-fc89728a9138" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationAxis_cd284dc5-17c9-4f9a-ad05-13eab427f6d4" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DisposalGroupClassificationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_8833a117-7841-4419-ba90-1f1ad5e61abe" xlink:to="loc_us-gaap_DisposalGroupClassificationAxis_cd284dc5-17c9-4f9a-ad05-13eab427f6d4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationDomain_cd284dc5-17c9-4f9a-ad05-13eab427f6d4_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DisposalGroupClassificationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DisposalGroupClassificationAxis_cd284dc5-17c9-4f9a-ad05-13eab427f6d4" xlink:to="loc_us-gaap_DisposalGroupClassificationDomain_cd284dc5-17c9-4f9a-ad05-13eab427f6d4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationDomain_d38a13fb-9dda-459b-8d0d-ba74fc3fc675" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DisposalGroupClassificationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DisposalGroupClassificationAxis_cd284dc5-17c9-4f9a-ad05-13eab427f6d4" xlink:to="loc_us-gaap_DisposalGroupClassificationDomain_d38a13fb-9dda-459b-8d0d-ba74fc3fc675" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupHeldforsaleNotDiscontinuedOperationsMember_477cee87-215f-468a-bfd5-26656cdc8767" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DisposalGroupHeldforsaleNotDiscontinuedOperationsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupClassificationDomain_d38a13fb-9dda-459b-8d0d-ba74fc3fc675" xlink:to="loc_us-gaap_DisposalGroupHeldforsaleNotDiscontinuedOperationsMember_477cee87-215f-468a-bfd5-26656cdc8767" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/GoodwillandOtherIntangiblesComponentsofIntangibleAssetsSubjecttoAmortizationDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#GoodwillandOtherIntangiblesComponentsofIntangibleAssetsSubjecttoAmortizationDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/GoodwillandOtherIntangiblesComponentsofIntangibleAssetsSubjecttoAmortizationDetails" xlink:type="extended" id="ie829251beec94da79249b2d25616d1fb_GoodwillandOtherIntangiblesComponentsofIntangibleAssetsSubjecttoAmortizationDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_e57b81e3-1650-4f87-b3fb-7058c6fa7423" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsRollForward_f77c7356-2803-4f97-bf5f-897704a01fa8" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_e57b81e3-1650-4f87-b3fb-7058c6fa7423" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsRollForward_f77c7356-2803-4f97-bf5f-897704a01fa8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsGross_a69a99c9-6704-4958-8bec-ed1ecde92e62" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsRollForward_f77c7356-2803-4f97-bf5f-897704a01fa8" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsGross_a69a99c9-6704-4958-8bec-ed1ecde92e62" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_FiniteLivedIntangibleAssetsPurchases_8f9f3602-6180-4a0a-ac00-088860557f2d" xlink:href="nrg-20201231.xsd#nrg_FiniteLivedIntangibleAssetsPurchases"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsRollForward_f77c7356-2803-4f97-bf5f-897704a01fa8" xlink:to="loc_nrg_FiniteLivedIntangibleAssetsPurchases_8f9f3602-6180-4a0a-ac00-088860557f2d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinitelivedIntangibleAssetsAcquired1_ec2b2f89-bdfc-4f89-a127-259cebf82848" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FinitelivedIntangibleAssetsAcquired1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsRollForward_f77c7356-2803-4f97-bf5f-897704a01fa8" xlink:to="loc_us-gaap_FinitelivedIntangibleAssetsAcquired1_ec2b2f89-bdfc-4f89-a127-259cebf82848" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_FiniteLivedIntangibleAssetsUsageAndRetirements_bb3a3c9b-7748-448e-8004-9d0a1554b91d" xlink:href="nrg-20201231.xsd#nrg_FiniteLivedIntangibleAssetsUsageAndRetirements"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsRollForward_f77c7356-2803-4f97-bf5f-897704a01fa8" xlink:to="loc_nrg_FiniteLivedIntangibleAssetsUsageAndRetirements_bb3a3c9b-7748-448e-8004-9d0a1554b91d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_FiniteLivedIntangibleAssetsWriteOffOfFullyAmortizedIntangibleAssets_2c62e338-58c2-4617-b4a6-64f3c29dd144" xlink:href="nrg-20201231.xsd#nrg_FiniteLivedIntangibleAssetsWriteOffOfFullyAmortizedIntangibleAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsRollForward_f77c7356-2803-4f97-bf5f-897704a01fa8" xlink:to="loc_nrg_FiniteLivedIntangibleAssetsWriteOffOfFullyAmortizedIntangibleAssets_2c62e338-58c2-4617-b4a6-64f3c29dd144" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ImpairmentOfIntangibleAssetsFinitelived_0c358ffa-42ac-4a05-b1f8-2f57a2ba6efe" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ImpairmentOfIntangibleAssetsFinitelived"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsRollForward_f77c7356-2803-4f97-bf5f-897704a01fa8" xlink:to="loc_us-gaap_ImpairmentOfIntangibleAssetsFinitelived_0c358ffa-42ac-4a05-b1f8-2f57a2ba6efe" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_FiniteLivedIntangibleAssetsOtherChanges_cb2584c9-569e-4285-ba54-47f0ed959a6e" xlink:href="nrg-20201231.xsd#nrg_FiniteLivedIntangibleAssetsOtherChanges"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsRollForward_f77c7356-2803-4f97-bf5f-897704a01fa8" xlink:to="loc_nrg_FiniteLivedIntangibleAssetsOtherChanges_cb2584c9-569e-4285-ba54-47f0ed959a6e" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsGross_34817e6b-fa65-4a04-922d-cb30d4fa6300" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsGross"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_2b204005-f4ea-4b83-942b-d76136e3d783" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_e57b81e3-1650-4f87-b3fb-7058c6fa7423" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_2b204005-f4ea-4b83-942b-d76136e3d783" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_e4f46fa7-5ae6-4b8d-b7a1-c048acc15ae6" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_e57b81e3-1650-4f87-b3fb-7058c6fa7423" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsNet_e4f46fa7-5ae6-4b8d-b7a1-c048acc15ae6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsWeightedAverageUsefulLife_dc73c69e-ddb8-403f-816a-367c8b0ca690" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AcquiredFiniteLivedIntangibleAssetsWeightedAverageUsefulLife"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_e57b81e3-1650-4f87-b3fb-7058c6fa7423" xlink:to="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsWeightedAverageUsefulLife_dc73c69e-ddb8-403f-816a-367c8b0ca690" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill_160f13a0-1e54-44bc-af5c-c339fe8e1a8c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_e57b81e3-1650-4f87-b3fb-7058c6fa7423" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill_160f13a0-1e54-44bc-af5c-c339fe8e1a8c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_1ed4f3d3-370f-4a0e-bee4-5611b33b098e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_e57b81e3-1650-4f87-b3fb-7058c6fa7423" xlink:to="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_1ed4f3d3-370f-4a0e-bee4-5611b33b098e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_df147a13-9adc-40c3-9539-0d0b0e2c90a6" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_1ed4f3d3-370f-4a0e-bee4-5611b33b098e" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_df147a13-9adc-40c3-9539-0d0b0e2c90a6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_df147a13-9adc-40c3-9539-0d0b0e2c90a6_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_df147a13-9adc-40c3-9539-0d0b0e2c90a6" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_df147a13-9adc-40c3-9539-0d0b0e2c90a6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_712056e9-292e-4a9a-8f83-9803db9e904b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_df147a13-9adc-40c3-9539-0d0b0e2c90a6" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_712056e9-292e-4a9a-8f83-9803db9e904b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_EmissionAllowancesMember_d690c1d1-7cf2-4c77-8352-6fe48b302235" xlink:href="nrg-20201231.xsd#nrg_EmissionAllowancesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_712056e9-292e-4a9a-8f83-9803db9e904b" xlink:to="loc_nrg_EmissionAllowancesMember_d690c1d1-7cf2-4c77-8352-6fe48b302235" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_FuelContractsMember_deed04cc-634c-42ff-8008-b2d26f1962f4" xlink:href="nrg-20201231.xsd#nrg_FuelContractsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_712056e9-292e-4a9a-8f83-9803db9e904b" xlink:to="loc_nrg_FuelContractsMember_deed04cc-634c-42ff-8008-b2d26f1962f4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerRelationshipsMember_e70a4ac9-9285-4bd3-8c39-ae1a46c73d3f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CustomerRelationshipsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_712056e9-292e-4a9a-8f83-9803db9e904b" xlink:to="loc_us-gaap_CustomerRelationshipsMember_e70a4ac9-9285-4bd3-8c39-ae1a46c73d3f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_MarketingPartnershipsMember_ee10b767-ea68-41d3-a474-b22ba0c83613" xlink:href="nrg-20201231.xsd#nrg_MarketingPartnershipsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_712056e9-292e-4a9a-8f83-9803db9e904b" xlink:to="loc_nrg_MarketingPartnershipsMember_ee10b767-ea68-41d3-a474-b22ba0c83613" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TradeNamesMember_ffe3b6ee-7882-4be0-b8be-13c4be13e465" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TradeNamesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_712056e9-292e-4a9a-8f83-9803db9e904b" xlink:to="loc_us-gaap_TradeNamesMember_ffe3b6ee-7882-4be0-b8be-13c4be13e465" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_OtherFiniteLivedIntangibleAssetsMember_c186e435-72ba-4416-82dd-385d3c668a10" xlink:href="nrg-20201231.xsd#nrg_OtherFiniteLivedIntangibleAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_712056e9-292e-4a9a-8f83-9803db9e904b" xlink:to="loc_nrg_OtherFiniteLivedIntangibleAssetsMember_c186e435-72ba-4416-82dd-385d3c668a10" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerContractsMember_14231879-8b57-458d-8191-60058b8ac653" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CustomerContractsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_712056e9-292e-4a9a-8f83-9803db9e904b" xlink:to="loc_us-gaap_CustomerContractsMember_14231879-8b57-458d-8191-60058b8ac653" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_9dc4d50f-59fb-4b7e-886d-e18a2ff96c1c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_1ed4f3d3-370f-4a0e-bee4-5611b33b098e" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_9dc4d50f-59fb-4b7e-886d-e18a2ff96c1c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_9dc4d50f-59fb-4b7e-886d-e18a2ff96c1c_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_9dc4d50f-59fb-4b7e-886d-e18a2ff96c1c" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_9dc4d50f-59fb-4b7e-886d-e18a2ff96c1c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_615e4c53-c3bd-4296-813c-2b9060657858" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_9dc4d50f-59fb-4b7e-886d-e18a2ff96c1c" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_615e4c53-c3bd-4296-813c-2b9060657858" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_RenewableEnergyCertificatesMember_54d64a60-461b-4d30-bc1c-f55350420e4d" xlink:href="nrg-20201231.xsd#nrg_RenewableEnergyCertificatesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_615e4c53-c3bd-4296-813c-2b9060657858" xlink:to="loc_nrg_RenewableEnergyCertificatesMember_54d64a60-461b-4d30-bc1c-f55350420e4d" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/GoodwillandOtherIntangiblesScheduleofAmortizationandRetirementofIntangibleAssetsDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#GoodwillandOtherIntangiblesScheduleofAmortizationandRetirementofIntangibleAssetsDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/GoodwillandOtherIntangiblesScheduleofAmortizationandRetirementofIntangibleAssetsDetails" xlink:type="extended" id="i61cb6f65ddc44571a625863bf67210e7_GoodwillandOtherIntangiblesScheduleofAmortizationandRetirementofIntangibleAssetsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_71e1155f-78d8-484a-a0e7-5bd9629c2730" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfIntangibleAssets_f11c87c2-8df0-4550-b3c8-c2465727a98c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AmortizationOfIntangibleAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_71e1155f-78d8-484a-a0e7-5bd9629c2730" xlink:to="loc_us-gaap_AmortizationOfIntangibleAssets_f11c87c2-8df0-4550-b3c8-c2465727a98c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_FiniteLivedIntangibleAssetRetirements_907df71c-7807-493c-811c-c424f45c1714" xlink:href="nrg-20201231.xsd#nrg_FiniteLivedIntangibleAssetRetirements"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_71e1155f-78d8-484a-a0e7-5bd9629c2730" xlink:to="loc_nrg_FiniteLivedIntangibleAssetRetirements_907df71c-7807-493c-811c-c424f45c1714" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepreciationAmortizationAndAccretionNet_fdd37902-a3ec-425a-ba47-a86725c4431a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DepreciationAmortizationAndAccretionNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_71e1155f-78d8-484a-a0e7-5bd9629c2730" xlink:to="loc_us-gaap_DepreciationAmortizationAndAccretionNet_fdd37902-a3ec-425a-ba47-a86725c4431a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_0e1fe965-e4e5-4148-9f64-2a652368b5d5" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_71e1155f-78d8-484a-a0e7-5bd9629c2730" xlink:to="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_0e1fe965-e4e5-4148-9f64-2a652368b5d5" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_242531b7-e100-4958-ad9e-77b691278a3e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_0e1fe965-e4e5-4148-9f64-2a652368b5d5" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_242531b7-e100-4958-ad9e-77b691278a3e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_242531b7-e100-4958-ad9e-77b691278a3e_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_242531b7-e100-4958-ad9e-77b691278a3e" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_242531b7-e100-4958-ad9e-77b691278a3e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_ae7204a8-6da8-49c9-99e2-ae0fdb49b710" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_242531b7-e100-4958-ad9e-77b691278a3e" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_ae7204a8-6da8-49c9-99e2-ae0fdb49b710" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_EmissionAllowancesMember_5893c867-a598-4649-bbe5-0752521feb8a" xlink:href="nrg-20201231.xsd#nrg_EmissionAllowancesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_ae7204a8-6da8-49c9-99e2-ae0fdb49b710" xlink:to="loc_nrg_EmissionAllowancesMember_5893c867-a598-4649-bbe5-0752521feb8a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerRelationshipsMember_167c2a1a-35ca-4664-bec0-521c0e2f1bd0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CustomerRelationshipsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_ae7204a8-6da8-49c9-99e2-ae0fdb49b710" xlink:to="loc_us-gaap_CustomerRelationshipsMember_167c2a1a-35ca-4664-bec0-521c0e2f1bd0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_MarketingPartnershipsMember_c37e64c9-2fad-4d13-b344-335bc6a3b0d9" xlink:href="nrg-20201231.xsd#nrg_MarketingPartnershipsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_ae7204a8-6da8-49c9-99e2-ae0fdb49b710" xlink:to="loc_nrg_MarketingPartnershipsMember_c37e64c9-2fad-4d13-b344-335bc6a3b0d9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TradeNamesMember_42970ff7-3eb9-46d5-834f-942b9e1cd924" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TradeNamesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_ae7204a8-6da8-49c9-99e2-ae0fdb49b710" xlink:to="loc_us-gaap_TradeNamesMember_42970ff7-3eb9-46d5-834f-942b9e1cd924" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_OtherFiniteLivedIntangibleAssetsMember_85bfa3f8-6079-4640-a263-1db9b9f8145d" xlink:href="nrg-20201231.xsd#nrg_OtherFiniteLivedIntangibleAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_ae7204a8-6da8-49c9-99e2-ae0fdb49b710" xlink:to="loc_nrg_OtherFiniteLivedIntangibleAssetsMember_85bfa3f8-6079-4640-a263-1db9b9f8145d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_7320a27e-a79d-4c91-bca1-f5435bdcd654" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_0e1fe965-e4e5-4148-9f64-2a652368b5d5" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_7320a27e-a79d-4c91-bca1-f5435bdcd654" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_7320a27e-a79d-4c91-bca1-f5435bdcd654_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_7320a27e-a79d-4c91-bca1-f5435bdcd654" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_7320a27e-a79d-4c91-bca1-f5435bdcd654_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_0563961d-2938-45b9-9e36-ed192f4246a3" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_7320a27e-a79d-4c91-bca1-f5435bdcd654" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_0563961d-2938-45b9-9e36-ed192f4246a3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_RenewableEnergyCertificatesMember_3b74818c-7622-45fc-b009-f6b776d20d49" xlink:href="nrg-20201231.xsd#nrg_RenewableEnergyCertificatesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_0563961d-2938-45b9-9e36-ed192f4246a3" xlink:to="loc_nrg_RenewableEnergyCertificatesMember_3b74818c-7622-45fc-b009-f6b776d20d49" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_ff3e9ca9-3159-494b-bd0d-6239e38d92d9" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeStatementLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_0e1fe965-e4e5-4148-9f64-2a652368b5d5" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_ff3e9ca9-3159-494b-bd0d-6239e38d92d9" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_ff3e9ca9-3159-494b-bd0d-6239e38d92d9_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_ff3e9ca9-3159-494b-bd0d-6239e38d92d9" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_ff3e9ca9-3159-494b-bd0d-6239e38d92d9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_b429b728-e0a0-4df2-920b-b34456596dd2" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_ff3e9ca9-3159-494b-bd0d-6239e38d92d9" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_b429b728-e0a0-4df2-920b-b34456596dd2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfSalesMember_3637a072-5a92-4ae9-b1fc-d0c3eaf572ea" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CostOfSalesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_b429b728-e0a0-4df2-920b-b34456596dd2" xlink:to="loc_us-gaap_CostOfSalesMember_3637a072-5a92-4ae9-b1fc-d0c3eaf572ea" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/GoodwillandOtherIntangiblesScheduleofEstimatedAmortizationofIntangibleAssetfortheNextFiveYearsDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#GoodwillandOtherIntangiblesScheduleofEstimatedAmortizationofIntangibleAssetfortheNextFiveYearsDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/GoodwillandOtherIntangiblesScheduleofEstimatedAmortizationofIntangibleAssetfortheNextFiveYearsDetails" xlink:type="extended" id="if6cf142fee364cf8b3125a76dce98a3b_GoodwillandOtherIntangiblesScheduleofEstimatedAmortizationofIntangibleAssetfortheNextFiveYearsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_ab188158-14c7-4da8-af4f-324d97dc804d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsFutureAmortizationExpenseAbstract_8b03d130-9e49-4dd5-8f4f-250c7360bb4b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsFutureAmortizationExpenseAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_ab188158-14c7-4da8-af4f-324d97dc804d" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsFutureAmortizationExpenseAbstract_8b03d130-9e49-4dd5-8f4f-250c7360bb4b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths_82453890-3496-49b1-a30e-4b7f6eac1066" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsFutureAmortizationExpenseAbstract_8b03d130-9e49-4dd5-8f4f-250c7360bb4b" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths_82453890-3496-49b1-a30e-4b7f6eac1066" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo_93b1cc93-3217-4a12-820c-7348342171bc" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsFutureAmortizationExpenseAbstract_8b03d130-9e49-4dd5-8f4f-250c7360bb4b" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo_93b1cc93-3217-4a12-820c-7348342171bc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearThree_dcd174aa-cec6-4a14-8a3b-a0f9f0fcf2fd" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearThree"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsFutureAmortizationExpenseAbstract_8b03d130-9e49-4dd5-8f4f-250c7360bb4b" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearThree_dcd174aa-cec6-4a14-8a3b-a0f9f0fcf2fd" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFour_b0005acb-8ceb-47bb-ba25-1934010e9077" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFour"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsFutureAmortizationExpenseAbstract_8b03d130-9e49-4dd5-8f4f-250c7360bb4b" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFour_b0005acb-8ceb-47bb-ba25-1934010e9077" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFive_daab402a-6c93-4559-86bb-618043a5d803" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFive"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsFutureAmortizationExpenseAbstract_8b03d130-9e49-4dd5-8f4f-250c7360bb4b" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFive_daab402a-6c93-4559-86bb-618043a5d803" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_328cc52f-89c7-406b-936e-1db6a7196e1e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_ab188158-14c7-4da8-af4f-324d97dc804d" xlink:to="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_328cc52f-89c7-406b-936e-1db6a7196e1e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_5804e129-2eb2-4738-bffd-29e345366193" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_328cc52f-89c7-406b-936e-1db6a7196e1e" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_5804e129-2eb2-4738-bffd-29e345366193" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_5804e129-2eb2-4738-bffd-29e345366193_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_5804e129-2eb2-4738-bffd-29e345366193" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_5804e129-2eb2-4738-bffd-29e345366193_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_f12f3493-d596-46c7-a4d8-a530ad9e9aa4" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_5804e129-2eb2-4738-bffd-29e345366193" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_f12f3493-d596-46c7-a4d8-a530ad9e9aa4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_EmissionAllowancesMember_7261af41-3daa-4f83-86f8-d344adb6cf23" xlink:href="nrg-20201231.xsd#nrg_EmissionAllowancesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_f12f3493-d596-46c7-a4d8-a530ad9e9aa4" xlink:to="loc_nrg_EmissionAllowancesMember_7261af41-3daa-4f83-86f8-d344adb6cf23" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_FuelContractsMember_3cd7f736-ce87-42b3-b716-cfec3b57d834" xlink:href="nrg-20201231.xsd#nrg_FuelContractsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_f12f3493-d596-46c7-a4d8-a530ad9e9aa4" xlink:to="loc_nrg_FuelContractsMember_3cd7f736-ce87-42b3-b716-cfec3b57d834" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerRelationshipsMember_8c3bcc29-5626-40d3-b78b-c83e237345fc" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CustomerRelationshipsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_f12f3493-d596-46c7-a4d8-a530ad9e9aa4" xlink:to="loc_us-gaap_CustomerRelationshipsMember_8c3bcc29-5626-40d3-b78b-c83e237345fc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_MarketingPartnershipsMember_5a07b40e-186d-49bb-bd16-32ebbb8f5dcc" xlink:href="nrg-20201231.xsd#nrg_MarketingPartnershipsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_f12f3493-d596-46c7-a4d8-a530ad9e9aa4" xlink:to="loc_nrg_MarketingPartnershipsMember_5a07b40e-186d-49bb-bd16-32ebbb8f5dcc" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TradeNamesMember_0c0b7e63-dcbe-4308-8520-9170ffa8eb1e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TradeNamesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_f12f3493-d596-46c7-a4d8-a530ad9e9aa4" xlink:to="loc_us-gaap_TradeNamesMember_0c0b7e63-dcbe-4308-8520-9170ffa8eb1e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_OtherFiniteLivedIntangibleAssetsMember_5c6ad2dd-b60f-47c7-8979-bea23a8c9326" xlink:href="nrg-20201231.xsd#nrg_OtherFiniteLivedIntangibleAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_f12f3493-d596-46c7-a4d8-a530ad9e9aa4" xlink:to="loc_nrg_OtherFiniteLivedIntangibleAssetsMember_5c6ad2dd-b60f-47c7-8979-bea23a8c9326" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/ReceivablesSecuritizationandRepurchaseFacility" xlink:type="simple" xlink:href="nrg-20201231.xsd#ReceivablesSecuritizationandRepurchaseFacility"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/ReceivablesSecuritizationandRepurchaseFacility" xlink:type="extended" id="i27230c24fcb94e87936e409a3381c5c9_ReceivablesSecuritizationandRepurchaseFacility"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/ReceivablesSecuritizationandRepurchaseFacilityDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#ReceivablesSecuritizationandRepurchaseFacilityDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/ReceivablesSecuritizationandRepurchaseFacilityDetails" xlink:type="extended" id="idefa578060424b5f90fdc274063c1911_ReceivablesSecuritizationandRepurchaseFacilityDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityLineItems_82b70246-d23b-4212-8fde-ace083fa0e6d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LineOfCreditFacilityLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_3f8c936d-8d8d-4d44-86de-8fd081366497" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_82b70246-d23b-4212-8fde-ace083fa0e6d" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_3f8c936d-8d8d-4d44-86de-8fd081366497" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtWeightedAverageInterestRate_0fa79145-4cd9-4bd4-81f3-1ba3fe91e7f8" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtWeightedAverageInterestRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_82b70246-d23b-4212-8fde-ace083fa0e6d" xlink:to="loc_us-gaap_DebtWeightedAverageInterestRate_0fa79145-4cd9-4bd4-81f3-1ba3fe91e7f8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LinesOfCreditCurrent_ff5a3fb0-ce43-452c-b62d-72a5966ea740" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LinesOfCreditCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_82b70246-d23b-4212-8fde-ace083fa0e6d" xlink:to="loc_us-gaap_LinesOfCreditCurrent_ff5a3fb0-ce43-452c-b62d-72a5966ea740" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LettersOfCreditOutstandingAmount_c4e25494-93a1-435f-bc74-3b3be7c00de4" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LettersOfCreditOutstandingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_82b70246-d23b-4212-8fde-ace083fa0e6d" xlink:to="loc_us-gaap_LettersOfCreditOutstandingAmount_c4e25494-93a1-435f-bc74-3b3be7c00de4" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityCommitmentFeeAmount_86c27ad0-1050-454e-a1fc-9a972419d23d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LineOfCreditFacilityCommitmentFeeAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_82b70246-d23b-4212-8fde-ace083fa0e6d" xlink:to="loc_us-gaap_LineOfCreditFacilityCommitmentFeeAmount_86c27ad0-1050-454e-a1fc-9a972419d23d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_7b619083-0d76-4921-8927-8a473ed532ea" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentBasisSpreadOnVariableRate1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_82b70246-d23b-4212-8fde-ace083fa0e6d" xlink:to="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_7b619083-0d76-4921-8927-8a473ed532ea" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityTable_a1279547-91b0-428b-97de-d0cca1d07116" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LineOfCreditFacilityTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_82b70246-d23b-4212-8fde-ace083fa0e6d" xlink:to="loc_us-gaap_LineOfCreditFacilityTable_a1279547-91b0-428b-97de-d0cca1d07116" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_7d0a3c8b-15ca-4bf1-8081-bace5899c68e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_a1279547-91b0-428b-97de-d0cca1d07116" xlink:to="loc_us-gaap_DebtInstrumentAxis_7d0a3c8b-15ca-4bf1-8081-bace5899c68e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_7d0a3c8b-15ca-4bf1-8081-bace5899c68e_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_7d0a3c8b-15ca-4bf1-8081-bace5899c68e" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_7d0a3c8b-15ca-4bf1-8081-bace5899c68e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_1e2fa416-7dde-4c32-a53c-bf7842666b61" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_7d0a3c8b-15ca-4bf1-8081-bace5899c68e" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_1e2fa416-7dde-4c32-a53c-bf7842666b61" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_ReceivablesFacilityMember_e42c0001-b86d-4710-b757-4ddf90e3d58f" xlink:href="nrg-20201231.xsd#nrg_ReceivablesFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_1e2fa416-7dde-4c32-a53c-bf7842666b61" xlink:to="loc_nrg_ReceivablesFacilityMember_e42c0001-b86d-4710-b757-4ddf90e3d58f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_RepurchaseFacilityMember_2d67b3da-5fd3-49a5-b806-36bfb196872e" xlink:href="nrg-20201231.xsd#nrg_RepurchaseFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_1e2fa416-7dde-4c32-a53c-bf7842666b61" xlink:to="loc_nrg_RepurchaseFacilityMember_2d67b3da-5fd3-49a5-b806-36bfb196872e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_b6759a38-35e1-4527-bae1-209f0a564683" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_a1279547-91b0-428b-97de-d0cca1d07116" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_b6759a38-35e1-4527-bae1-209f0a564683" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_b6759a38-35e1-4527-bae1-209f0a564683_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_b6759a38-35e1-4527-bae1-209f0a564683" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_b6759a38-35e1-4527-bae1-209f0a564683_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_707d0b20-94ed-4084-84e8-67bc1edce59a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_b6759a38-35e1-4527-bae1-209f0a564683" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_707d0b20-94ed-4084-84e8-67bc1edce59a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredDebtMember_8a33f51c-b7e7-479f-baef-00641f21832c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_707d0b20-94ed-4084-84e8-67bc1edce59a" xlink:to="loc_us-gaap_SecuredDebtMember_8a33f51c-b7e7-479f-baef-00641f21832c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_aa0c7f5a-6a70-48df-8b76-da191997ca21" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_a1279547-91b0-428b-97de-d0cca1d07116" xlink:to="loc_us-gaap_CreditFacilityAxis_aa0c7f5a-6a70-48df-8b76-da191997ca21" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_aa0c7f5a-6a70-48df-8b76-da191997ca21_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_aa0c7f5a-6a70-48df-8b76-da191997ca21" xlink:to="loc_us-gaap_CreditFacilityDomain_aa0c7f5a-6a70-48df-8b76-da191997ca21_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_c7ee6e32-cf29-43a9-8923-9efb01a7eb12" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_aa0c7f5a-6a70-48df-8b76-da191997ca21" xlink:to="loc_us-gaap_CreditFacilityDomain_c7ee6e32-cf29-43a9-8923-9efb01a7eb12" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LetterOfCreditMember_d8fd1a66-1130-48fd-b11d-a1a7d4540918" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LetterOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_c7ee6e32-cf29-43a9-8923-9efb01a7eb12" xlink:to="loc_us-gaap_LetterOfCreditMember_d8fd1a66-1130-48fd-b11d-a1a7d4540918" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateAxis_d9fc1a9e-c32f-4283-8883-4dfb43f9261f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_VariableRateAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_a1279547-91b0-428b-97de-d0cca1d07116" xlink:to="loc_us-gaap_VariableRateAxis_d9fc1a9e-c32f-4283-8883-4dfb43f9261f" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain_d9fc1a9e-c32f-4283-8883-4dfb43f9261f_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_VariableRateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_VariableRateAxis_d9fc1a9e-c32f-4283-8883-4dfb43f9261f" xlink:to="loc_us-gaap_VariableRateDomain_d9fc1a9e-c32f-4283-8883-4dfb43f9261f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain_a7d57526-5346-4b46-93fc-c800f7d81492" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_VariableRateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_VariableRateAxis_d9fc1a9e-c32f-4283-8883-4dfb43f9261f" xlink:to="loc_us-gaap_VariableRateDomain_a7d57526-5346-4b46-93fc-c800f7d81492" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LondonInterbankOfferedRateLIBORMember_7983de51-f8d6-4565-9635-ac3af27a9db4" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LondonInterbankOfferedRateLIBORMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_a7d57526-5346-4b46-93fc-c800f7d81492" xlink:to="loc_us-gaap_LondonInterbankOfferedRateLIBORMember_7983de51-f8d6-4565-9635-ac3af27a9db4" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/LongtermDebtandFinanceLeases" xlink:type="simple" xlink:href="nrg-20201231.xsd#LongtermDebtandFinanceLeases"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/LongtermDebtandFinanceLeases" xlink:type="extended" id="icae92d85e1f945fd985fdac615c28581_LongtermDebtandFinanceLeases"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/LongtermDebtandFinanceLeasesTables" xlink:type="simple" xlink:href="nrg-20201231.xsd#LongtermDebtandFinanceLeasesTables"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/LongtermDebtandFinanceLeasesTables" xlink:type="extended" id="i3ab8b650380e47d880bdc40fac952c10_LongtermDebtandFinanceLeasesTables"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/LongtermDebtandFinanceLeasesScheduleofLongtermDebtandFinanceLeasesDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#LongtermDebtandFinanceLeasesScheduleofLongtermDebtandFinanceLeasesDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/LongtermDebtandFinanceLeasesScheduleofLongtermDebtandFinanceLeasesDetails" xlink:type="extended" id="i17fd1388e85a4adaae8b508c29475766_LongtermDebtandFinanceLeasesScheduleofLongtermDebtandFinanceLeasesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_c91eca9b-c166-40fa-af0b-a41384d3b798" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_80ddb408-b598-412b-b105-b87117138dd5" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_c91eca9b-c166-40fa-af0b-a41384d3b798" xlink:to="loc_us-gaap_LongTermDebt_80ddb408-b598-412b-b105-b87117138dd5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseLiability_d54d78ed-c905-46c7-9be1-c8c31d91c6e2" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FinanceLeaseLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_c91eca9b-c166-40fa-af0b-a41384d3b798" xlink:to="loc_us-gaap_FinanceLeaseLiability_d54d78ed-c905-46c7-9be1-c8c31d91c6e2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtAndCapitalLeaseObligations_276762a9-6b32-4740-90b3-a0616ca53d83" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtAndCapitalLeaseObligations"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_c91eca9b-c166-40fa-af0b-a41384d3b798" xlink:to="loc_us-gaap_DebtAndCapitalLeaseObligations_276762a9-6b32-4740-90b3-a0616ca53d83" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtAndCapitalLeaseObligationsCurrent_01a0d258-e7e9-4ea5-a482-518ad6983535" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongTermDebtAndCapitalLeaseObligationsCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_c91eca9b-c166-40fa-af0b-a41384d3b798" xlink:to="loc_us-gaap_LongTermDebtAndCapitalLeaseObligationsCurrent_01a0d258-e7e9-4ea5-a482-518ad6983535" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredFinanceCostsNet_b0d4e0bd-255d-4a9b-a310-fb28af576c8c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredFinanceCostsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_c91eca9b-c166-40fa-af0b-a41384d3b798" xlink:to="loc_us-gaap_DeferredFinanceCostsNet_b0d4e0bd-255d-4a9b-a310-fb28af576c8c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentUnamortizedDiscountPremiumNet_58562b0c-a558-4b6f-bff4-193dcae99039" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentUnamortizedDiscountPremiumNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_c91eca9b-c166-40fa-af0b-a41384d3b798" xlink:to="loc_us-gaap_DebtInstrumentUnamortizedDiscountPremiumNet_58562b0c-a558-4b6f-bff4-193dcae99039" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtAndCapitalLeaseObligations_c71c12ef-e7f5-4414-8267-a57905980730" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongTermDebtAndCapitalLeaseObligations"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_c91eca9b-c166-40fa-af0b-a41384d3b798" xlink:to="loc_us-gaap_LongTermDebtAndCapitalLeaseObligations_c71c12ef-e7f5-4414-8267-a57905980730" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_49b2d2b1-e9a2-4e50-bc30-2cc6060eac06" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_c91eca9b-c166-40fa-af0b-a41384d3b798" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_49b2d2b1-e9a2-4e50-bc30-2cc6060eac06" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_20eaff71-a2ec-4599-a661-f8250504bc19" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentBasisSpreadOnVariableRate1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_c91eca9b-c166-40fa-af0b-a41384d3b798" xlink:to="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_20eaff71-a2ec-4599-a661-f8250504bc19" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateEffectivePercentage_b6e4dfb5-f612-472e-8f01-9b7d69dc1425" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentInterestRateEffectivePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_c91eca9b-c166-40fa-af0b-a41384d3b798" xlink:to="loc_us-gaap_DebtInstrumentInterestRateEffectivePercentage_b6e4dfb5-f612-472e-8f01-9b7d69dc1425" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentConvertibleConversionPrice1_48462b5a-43a3-4fef-9a27-631fef8b91de" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentConvertibleConversionPrice1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_c91eca9b-c166-40fa-af0b-a41384d3b798" xlink:to="loc_us-gaap_DebtInstrumentConvertibleConversionPrice1_48462b5a-43a3-4fef-9a27-631fef8b91de" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentConvertibleConversionRatio1_2e6d657a-ac56-4c80-902f-27f59034235e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentConvertibleConversionRatio1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_c91eca9b-c166-40fa-af0b-a41384d3b798" xlink:to="loc_us-gaap_DebtInstrumentConvertibleConversionRatio1_2e6d657a-ac56-4c80-902f-27f59034235e" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentConvertibleRemainingDiscountAmortizationPeriod1_0c8df84c-b8ae-4547-9264-3bdcdb38530f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentConvertibleRemainingDiscountAmortizationPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_c91eca9b-c166-40fa-af0b-a41384d3b798" xlink:to="loc_us-gaap_DebtInstrumentConvertibleRemainingDiscountAmortizationPeriod1_0c8df84c-b8ae-4547-9264-3bdcdb38530f" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentUnamortizedDiscountAbstract_3577da66-c295-48b9-8836-50f4421151fe" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentUnamortizedDiscountAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_c91eca9b-c166-40fa-af0b-a41384d3b798" xlink:to="loc_us-gaap_DebtInstrumentUnamortizedDiscountAbstract_3577da66-c295-48b9-8836-50f4421151fe" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentUnamortizedDiscountPremiumNet_c8c46a73-13bb-4cc0-a152-ecdff1a8468c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentUnamortizedDiscountPremiumNet"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_55d2398b-ff8e-4068-a232-c0209e66673c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_c91eca9b-c166-40fa-af0b-a41384d3b798" xlink:to="loc_us-gaap_DebtInstrumentTable_55d2398b-ff8e-4068-a232-c0209e66673c" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_371e3ca4-0f49-4386-bd20-3ed629f4b68c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_55d2398b-ff8e-4068-a232-c0209e66673c" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_371e3ca4-0f49-4386-bd20-3ed629f4b68c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_371e3ca4-0f49-4386-bd20-3ed629f4b68c_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_371e3ca4-0f49-4386-bd20-3ed629f4b68c" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_371e3ca4-0f49-4386-bd20-3ed629f4b68c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_dbe0b097-627b-44fe-9dbc-0caf8385b811" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_371e3ca4-0f49-4386-bd20-3ed629f4b68c" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_dbe0b097-627b-44fe-9dbc-0caf8385b811" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_RecourseDebtMember_7a2abc76-74ee-4f34-8649-207ce63f6863" xlink:href="nrg-20201231.xsd#nrg_RecourseDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_dbe0b097-627b-44fe-9dbc-0caf8385b811" xlink:to="loc_nrg_RecourseDebtMember_7a2abc76-74ee-4f34-8649-207ce63f6863" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_2226e2cc-44fb-4e45-89ef-0bdc9c48d1da" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_dbe0b097-627b-44fe-9dbc-0caf8385b811" xlink:to="loc_us-gaap_LineOfCreditMember_2226e2cc-44fb-4e45-89ef-0bdc9c48d1da" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_NonRecourseDebtMember_aaf0c6d2-cb92-465c-b660-6c7356ab2c5c" xlink:href="nrg-20201231.xsd#nrg_NonRecourseDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_dbe0b097-627b-44fe-9dbc-0caf8385b811" xlink:to="loc_nrg_NonRecourseDebtMember_aaf0c6d2-cb92-465c-b660-6c7356ab2c5c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_50b68dd3-7e24-4ff3-bc38-8bec6b36d72e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_55d2398b-ff8e-4068-a232-c0209e66673c" xlink:to="loc_us-gaap_DebtInstrumentAxis_50b68dd3-7e24-4ff3-bc38-8bec6b36d72e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_50b68dd3-7e24-4ff3-bc38-8bec6b36d72e_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_50b68dd3-7e24-4ff3-bc38-8bec6b36d72e" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_50b68dd3-7e24-4ff3-bc38-8bec6b36d72e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_22039650-0eef-4d69-9faa-ccf338384049" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_50b68dd3-7e24-4ff3-bc38-8bec6b36d72e" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_22039650-0eef-4d69-9faa-ccf338384049" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_SeniorNotesdue2026Member_625ed41e-c330-4efc-81a6-5d52e8a434cf" xlink:href="nrg-20201231.xsd#nrg_SeniorNotesdue2026Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_22039650-0eef-4d69-9faa-ccf338384049" xlink:to="loc_nrg_SeniorNotesdue2026Member_625ed41e-c330-4efc-81a6-5d52e8a434cf" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_SeniorNotesdue2027Member_ee726a3d-0ddd-46ce-acdc-15f29ab1d2c3" xlink:href="nrg-20201231.xsd#nrg_SeniorNotesdue2027Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_22039650-0eef-4d69-9faa-ccf338384049" xlink:to="loc_nrg_SeniorNotesdue2027Member_ee726a3d-0ddd-46ce-acdc-15f29ab1d2c3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_SeniorNotesdue2028Member_6b0ce87b-684e-41bf-bf4d-00beec5e7213" xlink:href="nrg-20201231.xsd#nrg_SeniorNotesdue2028Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_22039650-0eef-4d69-9faa-ccf338384049" xlink:to="loc_nrg_SeniorNotesdue2028Member_6b0ce87b-684e-41bf-bf4d-00beec5e7213" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_A525SeniorNotesDue2029Member_dc0a0c03-e1a8-40dc-b8c8-574d3492d540" xlink:href="nrg-20201231.xsd#nrg_A525SeniorNotesDue2029Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_22039650-0eef-4d69-9faa-ccf338384049" xlink:to="loc_nrg_A525SeniorNotesDue2029Member_dc0a0c03-e1a8-40dc-b8c8-574d3492d540" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_A3375SeniorUnsecuredNotesDue2029Member_f75c44f9-ba43-4a01-bbac-1b8733d98c93" xlink:href="nrg-20201231.xsd#nrg_A3375SeniorUnsecuredNotesDue2029Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_22039650-0eef-4d69-9faa-ccf338384049" xlink:to="loc_nrg_A3375SeniorUnsecuredNotesDue2029Member_f75c44f9-ba43-4a01-bbac-1b8733d98c93" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_A3625SeniorUnsecuredNotesDue2031Member_9a1c091f-3584-42a4-ad9a-b7fcfe4f40da" xlink:href="nrg-20201231.xsd#nrg_A3625SeniorUnsecuredNotesDue2031Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_22039650-0eef-4d69-9faa-ccf338384049" xlink:to="loc_nrg_A3625SeniorUnsecuredNotesDue2031Member_9a1c091f-3584-42a4-ad9a-b7fcfe4f40da" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_ConvertibleSeniorNotesDue2048Member_68db7129-7bd8-4ddc-b68d-dcff10061438" xlink:href="nrg-20201231.xsd#nrg_ConvertibleSeniorNotesDue2048Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_22039650-0eef-4d69-9faa-ccf338384049" xlink:to="loc_nrg_ConvertibleSeniorNotesDue2048Member_68db7129-7bd8-4ddc-b68d-dcff10061438" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_SeniorSecuredFirstLienNotesDue2024Member_3c4d0268-f1ec-4148-bf48-915db7581307" xlink:href="nrg-20201231.xsd#nrg_SeniorSecuredFirstLienNotesDue2024Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_22039650-0eef-4d69-9faa-ccf338384049" xlink:to="loc_nrg_SeniorSecuredFirstLienNotesDue2024Member_3c4d0268-f1ec-4148-bf48-915db7581307" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_A2000SeniorSecuredNotesDue2025Member_ef9297a4-7ffa-46ca-8e9e-1ca871217f05" xlink:href="nrg-20201231.xsd#nrg_A2000SeniorSecuredNotesDue2025Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_22039650-0eef-4d69-9faa-ccf338384049" xlink:to="loc_nrg_A2000SeniorSecuredNotesDue2025Member_ef9297a4-7ffa-46ca-8e9e-1ca871217f05" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_A2450SeniorSecuredNotesDue2027Member_997549a8-f67d-4802-8bef-52029018ba46" xlink:href="nrg-20201231.xsd#nrg_A2450SeniorSecuredNotesDue2027Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_22039650-0eef-4d69-9faa-ccf338384049" xlink:to="loc_nrg_A2450SeniorSecuredNotesDue2027Member_997549a8-f67d-4802-8bef-52029018ba46" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_SeniorSecuredFirstLienNotesDue2029Member_271c990d-e6eb-4544-9aaa-0ea19ed3836a" xlink:href="nrg-20201231.xsd#nrg_SeniorSecuredFirstLienNotesDue2029Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_22039650-0eef-4d69-9faa-ccf338384049" xlink:to="loc_nrg_SeniorSecuredFirstLienNotesDue2029Member_271c990d-e6eb-4544-9aaa-0ea19ed3836a" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_CreditAgreementMember_ab73e058-368f-4261-ad21-9e944118d68b" xlink:href="nrg-20201231.xsd#nrg_CreditAgreementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_22039650-0eef-4d69-9faa-ccf338384049" xlink:to="loc_nrg_CreditAgreementMember_ab73e058-368f-4261-ad21-9e944118d68b" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_TaxexemptBondsMember_37e6fbd3-b682-48dc-b7b7-3a1038f6a351" xlink:href="nrg-20201231.xsd#nrg_TaxexemptBondsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_22039650-0eef-4d69-9faa-ccf338384049" xlink:to="loc_nrg_TaxexemptBondsMember_37e6fbd3-b682-48dc-b7b7-3a1038f6a351" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_OtherDebtMember_42e0eaea-8f88-4aa8-8d3c-0969478cec1b" xlink:href="nrg-20201231.xsd#nrg_OtherDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_22039650-0eef-4d69-9faa-ccf338384049" xlink:to="loc_nrg_OtherDebtMember_42e0eaea-8f88-4aa8-8d3c-0969478cec1b" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_SeniorSecuredFirstLienNotesDue202420252027And2029Member_b78d318b-9398-498e-bdf1-400d8648b4d6" xlink:href="nrg-20201231.xsd#nrg_SeniorSecuredFirstLienNotesDue202420252027And2029Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_22039650-0eef-4d69-9faa-ccf338384049" xlink:to="loc_nrg_SeniorSecuredFirstLienNotesDue202420252027And2029Member_b78d318b-9398-498e-bdf1-400d8648b4d6" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_d02e1ea5-9619-4beb-804d-3f98c0cc6e43" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_55d2398b-ff8e-4068-a232-c0209e66673c" xlink:to="loc_us-gaap_CreditFacilityAxis_d02e1ea5-9619-4beb-804d-3f98c0cc6e43" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_d02e1ea5-9619-4beb-804d-3f98c0cc6e43_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_d02e1ea5-9619-4beb-804d-3f98c0cc6e43" xlink:to="loc_us-gaap_CreditFacilityDomain_d02e1ea5-9619-4beb-804d-3f98c0cc6e43_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_0025c763-329c-4dc7-9f05-c2ead986a4d2" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_d02e1ea5-9619-4beb-804d-3f98c0cc6e43" xlink:to="loc_us-gaap_CreditFacilityDomain_0025c763-329c-4dc7-9f05-c2ead986a4d2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_32a8a344-6bdf-4c59-9988-9241d4c5c4da" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_0025c763-329c-4dc7-9f05-c2ead986a4d2" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_32a8a344-6bdf-4c59-9988-9241d4c5c4da" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateAxis_1ca0deb1-7b27-4557-b153-7e4ce4a20ad3" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_VariableRateAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_55d2398b-ff8e-4068-a232-c0209e66673c" xlink:to="loc_us-gaap_VariableRateAxis_1ca0deb1-7b27-4557-b153-7e4ce4a20ad3" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain_1ca0deb1-7b27-4557-b153-7e4ce4a20ad3_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_VariableRateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_VariableRateAxis_1ca0deb1-7b27-4557-b153-7e4ce4a20ad3" xlink:to="loc_us-gaap_VariableRateDomain_1ca0deb1-7b27-4557-b153-7e4ce4a20ad3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain_192b5b2f-e480-403b-84d5-86189c12c79e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_VariableRateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_VariableRateAxis_1ca0deb1-7b27-4557-b153-7e4ce4a20ad3" xlink:to="loc_us-gaap_VariableRateDomain_192b5b2f-e480-403b-84d5-86189c12c79e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LondonInterbankOfferedRateLIBORMember_51f8d47a-32d6-44eb-a9e5-827f5a9951f5" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LondonInterbankOfferedRateLIBORMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_192b5b2f-e480-403b-84d5-86189c12c79e" xlink:to="loc_us-gaap_LondonInterbankOfferedRateLIBORMember_51f8d47a-32d6-44eb-a9e5-827f5a9951f5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_659d4323-1766-4852-9134-020b5e3ca967" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_55d2398b-ff8e-4068-a232-c0209e66673c" xlink:to="loc_srt_RangeAxis_659d4323-1766-4852-9134-020b5e3ca967" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_659d4323-1766-4852-9134-020b5e3ca967_default" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_659d4323-1766-4852-9134-020b5e3ca967" xlink:to="loc_srt_RangeMember_659d4323-1766-4852-9134-020b5e3ca967_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_5d8b0685-3988-483c-9e7a-c5f6082a1f33" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_659d4323-1766-4852-9134-020b5e3ca967" xlink:to="loc_srt_RangeMember_5d8b0685-3988-483c-9e7a-c5f6082a1f33" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_260d63a5-17ec-4312-841b-9394472aa50d" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_5d8b0685-3988-483c-9e7a-c5f6082a1f33" xlink:to="loc_srt_MinimumMember_260d63a5-17ec-4312-841b-9394472aa50d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_a690f8b2-8a83-4195-8248-bf6378563bb7" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_5d8b0685-3988-483c-9e7a-c5f6082a1f33" xlink:to="loc_srt_MaximumMember_a690f8b2-8a83-4195-8248-bf6378563bb7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_2aeb75cc-3906-4c43-9e56-5320714ae284" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_55d2398b-ff8e-4068-a232-c0209e66673c" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_2aeb75cc-3906-4c43-9e56-5320714ae284" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_2aeb75cc-3906-4c43-9e56-5320714ae284_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_2aeb75cc-3906-4c43-9e56-5320714ae284" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_2aeb75cc-3906-4c43-9e56-5320714ae284_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_3be56c55-2828-42c0-a7a1-178d5ec6d686" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_2aeb75cc-3906-4c43-9e56-5320714ae284" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_3be56c55-2828-42c0-a7a1-178d5ec6d686" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_a17962a9-bca3-46bb-b028-07aba32203cc" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_3be56c55-2828-42c0-a7a1-178d5ec6d686" xlink:to="loc_us-gaap_SubsequentEventMember_a17962a9-bca3-46bb-b028-07aba32203cc" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/LongtermDebtandFinanceLeasesAnnualPaymentsBasedontheMaturitiesofDebtandCapitalLeasesDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#LongtermDebtandFinanceLeasesAnnualPaymentsBasedontheMaturitiesofDebtandCapitalLeasesDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/LongtermDebtandFinanceLeasesAnnualPaymentsBasedontheMaturitiesofDebtandCapitalLeasesDetails" xlink:type="extended" id="id3f72fdf274745f68835b17037ed3138_LongtermDebtandFinanceLeasesAnnualPaymentsBasedontheMaturitiesofDebtandCapitalLeasesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_fa7d3f1a-faf4-4674-97c4-a23289af453f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths_9d4223af-8e98-44b9-b618-0b31b5a88aa4" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_fa7d3f1a-faf4-4674-97c4-a23289af453f" xlink:to="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths_9d4223af-8e98-44b9-b618-0b31b5a88aa4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo_559101a3-df40-4973-9818-eabaeb15c948" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_fa7d3f1a-faf4-4674-97c4-a23289af453f" xlink:to="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo_559101a3-df40-4973-9818-eabaeb15c948" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree_ff598102-51d8-45e1-a5f9-e0cf47545ec0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_fa7d3f1a-faf4-4674-97c4-a23289af453f" xlink:to="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree_ff598102-51d8-45e1-a5f9-e0cf47545ec0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour_c3aa13a4-bd85-42e5-b3b4-b64118db694f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_fa7d3f1a-faf4-4674-97c4-a23289af453f" xlink:to="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour_c3aa13a4-bd85-42e5-b3b4-b64118db694f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFive_997fee21-b43b-45b4-9e20-c8d220c82646" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFive"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_fa7d3f1a-faf4-4674-97c4-a23289af453f" xlink:to="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFive_997fee21-b43b-45b4-9e20-c8d220c82646" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalAfterYearFive_3cfc55b3-be85-43f4-8bdf-c985ea47b448" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalAfterYearFive"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_fa7d3f1a-faf4-4674-97c4-a23289af453f" xlink:to="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalAfterYearFive_3cfc55b3-be85-43f4-8bdf-c985ea47b448" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtAndCapitalLeaseObligations_e6ddca71-f4e9-4cd3-a92f-7eb428edc32b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtAndCapitalLeaseObligations"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_fa7d3f1a-faf4-4674-97c4-a23289af453f" xlink:to="loc_us-gaap_DebtAndCapitalLeaseObligations_e6ddca71-f4e9-4cd3-a92f-7eb428edc32b" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_c335ccf7-8229-4a05-8c1d-62b8b73979a4" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_fa7d3f1a-faf4-4674-97c4-a23289af453f" xlink:to="loc_us-gaap_DebtInstrumentTable_c335ccf7-8229-4a05-8c1d-62b8b73979a4" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_59534dd6-3b18-4ca0-b811-2037bacfca33" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_c335ccf7-8229-4a05-8c1d-62b8b73979a4" xlink:to="loc_us-gaap_CreditFacilityAxis_59534dd6-3b18-4ca0-b811-2037bacfca33" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_59534dd6-3b18-4ca0-b811-2037bacfca33_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_59534dd6-3b18-4ca0-b811-2037bacfca33" xlink:to="loc_us-gaap_CreditFacilityDomain_59534dd6-3b18-4ca0-b811-2037bacfca33_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_43a68741-2461-4d27-8502-97bd21da1570" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_59534dd6-3b18-4ca0-b811-2037bacfca33" xlink:to="loc_us-gaap_CreditFacilityDomain_43a68741-2461-4d27-8502-97bd21da1570" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_64f55e64-c513-4dc4-a990-8366905904e4" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_43a68741-2461-4d27-8502-97bd21da1570" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_64f55e64-c513-4dc4-a990-8366905904e4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_c13902ff-7a08-4d4e-9085-cd58315abae7" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_c335ccf7-8229-4a05-8c1d-62b8b73979a4" xlink:to="loc_us-gaap_DebtInstrumentAxis_c13902ff-7a08-4d4e-9085-cd58315abae7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_c13902ff-7a08-4d4e-9085-cd58315abae7_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_c13902ff-7a08-4d4e-9085-cd58315abae7" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_c13902ff-7a08-4d4e-9085-cd58315abae7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_7f2a6e23-20d9-4e2a-8fb6-0703923b2278" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_c13902ff-7a08-4d4e-9085-cd58315abae7" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_7f2a6e23-20d9-4e2a-8fb6-0703923b2278" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_CreditAgreementMember_71073329-4ed7-4c4b-92af-a4922761de4d" xlink:href="nrg-20201231.xsd#nrg_CreditAgreementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_7f2a6e23-20d9-4e2a-8fb6-0703923b2278" xlink:to="loc_nrg_CreditAgreementMember_71073329-4ed7-4c4b-92af-a4922761de4d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_2f748f96-d1e4-4a2d-904c-7979717a69dd" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_c335ccf7-8229-4a05-8c1d-62b8b73979a4" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_2f748f96-d1e4-4a2d-904c-7979717a69dd" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_2f748f96-d1e4-4a2d-904c-7979717a69dd_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_2f748f96-d1e4-4a2d-904c-7979717a69dd" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_2f748f96-d1e4-4a2d-904c-7979717a69dd_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_51547319-8e32-49c8-b5ab-bb1323231720" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_2f748f96-d1e4-4a2d-904c-7979717a69dd" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_51547319-8e32-49c8-b5ab-bb1323231720" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_1e8475b9-67fb-439a-9367-2c384354459f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_51547319-8e32-49c8-b5ab-bb1323231720" xlink:to="loc_us-gaap_LineOfCreditMember_1e8475b9-67fb-439a-9367-2c384354459f" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/LongtermDebtandFinanceLeasesIssuanceofSeniorNotesDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#LongtermDebtandFinanceLeasesIssuanceofSeniorNotesDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/LongtermDebtandFinanceLeasesIssuanceofSeniorNotesDetails" xlink:type="extended" id="i9c8db7c3e8704e969bb6a5dacca485a8_LongtermDebtandFinanceLeasesIssuanceofSeniorNotesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_b30b76e7-1cf8-4757-b14f-50f109078df3" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_86e60f60-b7e2-41e7-87f8-e5d3dba5be91" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_b30b76e7-1cf8-4757-b14f-50f109078df3" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_86e60f60-b7e2-41e7-87f8-e5d3dba5be91" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_59276e00-7abc-4149-a360-dd445430f590" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_b30b76e7-1cf8-4757-b14f-50f109078df3" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_59276e00-7abc-4149-a360-dd445430f590" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_DebtInstrumentBasisSpreadOnVariableRateIncrease_bc9d8623-6382-47b4-a926-db6bb11be749" xlink:href="nrg-20201231.xsd#nrg_DebtInstrumentBasisSpreadOnVariableRateIncrease"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_b30b76e7-1cf8-4757-b14f-50f109078df3" xlink:to="loc_nrg_DebtInstrumentBasisSpreadOnVariableRateIncrease_bc9d8623-6382-47b4-a926-db6bb11be749" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_da2c1aae-6bc3-4c6d-8840-ae29579a5fbc" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_b30b76e7-1cf8-4757-b14f-50f109078df3" xlink:to="loc_us-gaap_DebtInstrumentTable_da2c1aae-6bc3-4c6d-8840-ae29579a5fbc" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_35704ddb-83d4-4e7b-baf1-d785a4a12448" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_da2c1aae-6bc3-4c6d-8840-ae29579a5fbc" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_35704ddb-83d4-4e7b-baf1-d785a4a12448" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_35704ddb-83d4-4e7b-baf1-d785a4a12448_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_35704ddb-83d4-4e7b-baf1-d785a4a12448" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_35704ddb-83d4-4e7b-baf1-d785a4a12448_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_9b457c23-7a7e-499c-b9b8-b37f236e10f7" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_35704ddb-83d4-4e7b-baf1-d785a4a12448" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_9b457c23-7a7e-499c-b9b8-b37f236e10f7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_RecourseDebtMember_a77ecbaf-44c0-438d-9ace-d6acbd29f1d3" xlink:href="nrg-20201231.xsd#nrg_RecourseDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_9b457c23-7a7e-499c-b9b8-b37f236e10f7" xlink:to="loc_nrg_RecourseDebtMember_a77ecbaf-44c0-438d-9ace-d6acbd29f1d3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_1ca83ad0-60e1-4aa4-be89-d41f11ff71b6" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_da2c1aae-6bc3-4c6d-8840-ae29579a5fbc" xlink:to="loc_us-gaap_DebtInstrumentAxis_1ca83ad0-60e1-4aa4-be89-d41f11ff71b6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_1ca83ad0-60e1-4aa4-be89-d41f11ff71b6_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_1ca83ad0-60e1-4aa4-be89-d41f11ff71b6" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_1ca83ad0-60e1-4aa4-be89-d41f11ff71b6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_fb88fd60-c022-4f71-9889-eb90912a75e4" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_1ca83ad0-60e1-4aa4-be89-d41f11ff71b6" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_fb88fd60-c022-4f71-9889-eb90912a75e4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_A3375SeniorUnsecuredNotesDue2029Member_3aa0b89f-184e-4729-ba4b-8575b8c28a00" xlink:href="nrg-20201231.xsd#nrg_A3375SeniorUnsecuredNotesDue2029Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_fb88fd60-c022-4f71-9889-eb90912a75e4" xlink:to="loc_nrg_A3375SeniorUnsecuredNotesDue2029Member_3aa0b89f-184e-4729-ba4b-8575b8c28a00" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_A3625SeniorUnsecuredNotesDue2031Member_b960c9c4-55f3-4ec6-be4b-e590968d11d0" xlink:href="nrg-20201231.xsd#nrg_A3625SeniorUnsecuredNotesDue2031Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_fb88fd60-c022-4f71-9889-eb90912a75e4" xlink:to="loc_nrg_A3625SeniorUnsecuredNotesDue2031Member_b960c9c4-55f3-4ec6-be4b-e590968d11d0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_SeniorSecuredFirstLienNotesDue2025To2027Member_cee36e2d-9583-4747-860a-5dfd8f0f17ba" xlink:href="nrg-20201231.xsd#nrg_SeniorSecuredFirstLienNotesDue2025To2027Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_fb88fd60-c022-4f71-9889-eb90912a75e4" xlink:to="loc_nrg_SeniorSecuredFirstLienNotesDue2025To2027Member_cee36e2d-9583-4747-860a-5dfd8f0f17ba" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_A2000SeniorSecuredNotesDue2025Member_8dfb9ea4-af45-409f-93e7-d0a9c13522f5" xlink:href="nrg-20201231.xsd#nrg_A2000SeniorSecuredNotesDue2025Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_fb88fd60-c022-4f71-9889-eb90912a75e4" xlink:to="loc_nrg_A2000SeniorSecuredNotesDue2025Member_8dfb9ea4-af45-409f-93e7-d0a9c13522f5" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_A2450SeniorSecuredNotesDue2027Member_01f116f9-40ad-461a-9613-f6aa033841d6" xlink:href="nrg-20201231.xsd#nrg_A2450SeniorSecuredNotesDue2027Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_fb88fd60-c022-4f71-9889-eb90912a75e4" xlink:to="loc_nrg_A2450SeniorSecuredNotesDue2027Member_01f116f9-40ad-461a-9613-f6aa033841d6" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_A525SeniorNotesDue2029Member_905d8270-fb0b-4069-acb9-98f598e0a011" xlink:href="nrg-20201231.xsd#nrg_A525SeniorNotesDue2029Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_fb88fd60-c022-4f71-9889-eb90912a75e4" xlink:to="loc_nrg_A525SeniorNotesDue2029Member_905d8270-fb0b-4069-acb9-98f598e0a011" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_SeniorNotes2024Member_aeb56d07-88e3-4f0b-b0d1-abbdcde2a1be" xlink:href="nrg-20201231.xsd#nrg_SeniorNotes2024Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_fb88fd60-c022-4f71-9889-eb90912a75e4" xlink:to="loc_nrg_SeniorNotes2024Member_aeb56d07-88e3-4f0b-b0d1-abbdcde2a1be" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_SeniorSecuredFirstLienNotesDue2024And2029Member_93a49136-7386-4b1f-bad3-c67766b02240" xlink:href="nrg-20201231.xsd#nrg_SeniorSecuredFirstLienNotesDue2024And2029Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_fb88fd60-c022-4f71-9889-eb90912a75e4" xlink:to="loc_nrg_SeniorSecuredFirstLienNotesDue2024And2029Member_93a49136-7386-4b1f-bad3-c67766b02240" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_SeniorSecuredFirstLienNotesDue2024Member_c1951bd8-2fc4-4d54-b545-b818ab5e48b6" xlink:href="nrg-20201231.xsd#nrg_SeniorSecuredFirstLienNotesDue2024Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_fb88fd60-c022-4f71-9889-eb90912a75e4" xlink:to="loc_nrg_SeniorSecuredFirstLienNotesDue2024Member_c1951bd8-2fc4-4d54-b545-b818ab5e48b6" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_SeniorSecuredFirstLienNotesDue2029Member_5c832e2a-c174-44b3-b921-c26c2e85caa9" xlink:href="nrg-20201231.xsd#nrg_SeniorSecuredFirstLienNotesDue2029Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_fb88fd60-c022-4f71-9889-eb90912a75e4" xlink:to="loc_nrg_SeniorSecuredFirstLienNotesDue2029Member_5c832e2a-c174-44b3-b921-c26c2e85caa9" xlink:type="arc" order="9"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/LongtermDebtandFinanceLeasesSeniorNotesRedemptionandRepurchasesDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#LongtermDebtandFinanceLeasesSeniorNotesRedemptionandRepurchasesDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/LongtermDebtandFinanceLeasesSeniorNotesRedemptionandRepurchasesDetails" xlink:type="extended" id="i064b7670b9c4454bbc387ce1c433801c_LongtermDebtandFinanceLeasesSeniorNotesRedemptionandRepurchasesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_6e46904e-d567-4248-9418-98ded4538869" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRepurchaseAmount_6cc48fbb-d75c-4e7e-abef-c98689220eb8" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentRepurchaseAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_6e46904e-d567-4248-9418-98ded4538869" xlink:to="loc_us-gaap_DebtInstrumentRepurchaseAmount_6cc48fbb-d75c-4e7e-abef-c98689220eb8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_38fc1ac9-c24d-44b9-97e2-c3d19ff110e1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_6e46904e-d567-4248-9418-98ded4538869" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_38fc1ac9-c24d-44b9-97e2-c3d19ff110e1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainsLossesOnExtinguishmentOfDebt_bfbd14e2-a3c6-405d-9dc2-60e0d6b9daa7" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GainsLossesOnExtinguishmentOfDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_6e46904e-d567-4248-9418-98ded4538869" xlink:to="loc_us-gaap_GainsLossesOnExtinguishmentOfDebt_bfbd14e2-a3c6-405d-9dc2-60e0d6b9daa7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WriteOffOfDeferredDebtIssuanceCost_981c43b9-63bf-4d91-a82b-3197026974a0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_WriteOffOfDeferredDebtIssuanceCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_6e46904e-d567-4248-9418-98ded4538869" xlink:to="loc_us-gaap_WriteOffOfDeferredDebtIssuanceCost_981c43b9-63bf-4d91-a82b-3197026974a0" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_3e770b9d-bc00-403d-8281-8e7bc85f93fa" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_6e46904e-d567-4248-9418-98ded4538869" xlink:to="loc_us-gaap_DebtInstrumentTable_3e770b9d-bc00-403d-8281-8e7bc85f93fa" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_4057042f-2d36-4449-a5df-b3747bf305e7" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_3e770b9d-bc00-403d-8281-8e7bc85f93fa" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_4057042f-2d36-4449-a5df-b3747bf305e7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_4057042f-2d36-4449-a5df-b3747bf305e7_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_4057042f-2d36-4449-a5df-b3747bf305e7" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_4057042f-2d36-4449-a5df-b3747bf305e7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_4e05888f-f44c-4ad5-99df-c21893882f82" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_4057042f-2d36-4449-a5df-b3747bf305e7" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_4e05888f-f44c-4ad5-99df-c21893882f82" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_RecourseDebtMember_03376815-6fcd-4d8b-a3cd-e97c7fd08755" xlink:href="nrg-20201231.xsd#nrg_RecourseDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_4e05888f-f44c-4ad5-99df-c21893882f82" xlink:to="loc_nrg_RecourseDebtMember_03376815-6fcd-4d8b-a3cd-e97c7fd08755" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_9b307caa-d028-42d4-a4f8-d6644ef28b98" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_3e770b9d-bc00-403d-8281-8e7bc85f93fa" xlink:to="loc_us-gaap_DebtInstrumentAxis_9b307caa-d028-42d4-a4f8-d6644ef28b98" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_9b307caa-d028-42d4-a4f8-d6644ef28b98_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_9b307caa-d028-42d4-a4f8-d6644ef28b98" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_9b307caa-d028-42d4-a4f8-d6644ef28b98_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_16e37b4b-acf8-4956-ba72-ff3a47b46548" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_9b307caa-d028-42d4-a4f8-d6644ef28b98" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_16e37b4b-acf8-4956-ba72-ff3a47b46548" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_SeniorNotes2024Member_9dd3caec-52ad-43b6-aab3-ab6fc85ac7fd" xlink:href="nrg-20201231.xsd#nrg_SeniorNotes2024Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_16e37b4b-acf8-4956-ba72-ff3a47b46548" xlink:to="loc_nrg_SeniorNotes2024Member_9dd3caec-52ad-43b6-aab3-ab6fc85ac7fd" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/LongtermDebtandFinanceLeasesIssuanceofConvertibleSeniorNotesDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#LongtermDebtandFinanceLeasesIssuanceofConvertibleSeniorNotesDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/LongtermDebtandFinanceLeasesIssuanceofConvertibleSeniorNotesDetails" xlink:type="extended" id="i6060a8fd04f1463099c1a8610542fc7a_LongtermDebtandFinanceLeasesIssuanceofConvertibleSeniorNotesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_1117756c-b7ba-4bd9-80ec-d1575225c3cf" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentConvertibleConversionPrice1_e14a9768-b98c-4a1a-9383-cb419d742c52" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentConvertibleConversionPrice1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_1117756c-b7ba-4bd9-80ec-d1575225c3cf" xlink:to="loc_us-gaap_DebtInstrumentConvertibleConversionPrice1_e14a9768-b98c-4a1a-9383-cb419d742c52" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentConvertibleConversionRatio1_a8c5cf5f-a845-4308-b31b-ad7c0e3244c2" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentConvertibleConversionRatio1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_1117756c-b7ba-4bd9-80ec-d1575225c3cf" xlink:to="loc_us-gaap_DebtInstrumentConvertibleConversionRatio1_a8c5cf5f-a845-4308-b31b-ad7c0e3244c2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentConvertibleCarryingAmountOfTheEquityComponent_fdda4fad-5e1e-4ae5-a97b-f9a559d11347" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentConvertibleCarryingAmountOfTheEquityComponent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_1117756c-b7ba-4bd9-80ec-d1575225c3cf" xlink:to="loc_us-gaap_DebtInstrumentConvertibleCarryingAmountOfTheEquityComponent_fdda4fad-5e1e-4ae5-a97b-f9a559d11347" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_dd025871-2791-4600-9eab-0dc6ad21ee65" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_1117756c-b7ba-4bd9-80ec-d1575225c3cf" xlink:to="loc_us-gaap_DebtInstrumentTable_dd025871-2791-4600-9eab-0dc6ad21ee65" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_ee5d60c6-26f6-4281-bff4-d4636650e673" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_dd025871-2791-4600-9eab-0dc6ad21ee65" xlink:to="loc_us-gaap_DebtInstrumentAxis_ee5d60c6-26f6-4281-bff4-d4636650e673" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_ee5d60c6-26f6-4281-bff4-d4636650e673_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_ee5d60c6-26f6-4281-bff4-d4636650e673" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_ee5d60c6-26f6-4281-bff4-d4636650e673_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_03624f3d-cc6e-41a4-b149-4643721fa45f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_ee5d60c6-26f6-4281-bff4-d4636650e673" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_03624f3d-cc6e-41a4-b149-4643721fa45f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_ConvertibleSeniorNotesDue2048Member_9d11a436-05d1-4d68-a07e-baeaa0651598" xlink:href="nrg-20201231.xsd#nrg_ConvertibleSeniorNotesDue2048Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_03624f3d-cc6e-41a4-b149-4643721fa45f" xlink:to="loc_nrg_ConvertibleSeniorNotesDue2048Member_9d11a436-05d1-4d68-a07e-baeaa0651598" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_17d7299c-33c2-46a0-b4ae-3a84f5617611" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_dd025871-2791-4600-9eab-0dc6ad21ee65" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_17d7299c-33c2-46a0-b4ae-3a84f5617611" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_17d7299c-33c2-46a0-b4ae-3a84f5617611_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_17d7299c-33c2-46a0-b4ae-3a84f5617611" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_17d7299c-33c2-46a0-b4ae-3a84f5617611_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_2df34fc7-a790-4abd-9149-88b1ec92b87d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_17d7299c-33c2-46a0-b4ae-3a84f5617611" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_2df34fc7-a790-4abd-9149-88b1ec92b87d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_RecourseDebtMember_47771739-1bfb-4fcd-8e71-ee5655624c8c" xlink:href="nrg-20201231.xsd#nrg_RecourseDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_2df34fc7-a790-4abd-9149-88b1ec92b87d" xlink:to="loc_nrg_RecourseDebtMember_47771739-1bfb-4fcd-8e71-ee5655624c8c" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/LongtermDebtandFinanceLeasesSeniorNotesOutstandingwithEarlyRedemptionFeaturesDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#LongtermDebtandFinanceLeasesSeniorNotesOutstandingwithEarlyRedemptionFeaturesDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/LongtermDebtandFinanceLeasesSeniorNotesOutstandingwithEarlyRedemptionFeaturesDetails" xlink:type="extended" id="if140f13165aa4dc8be50d366f5388baf_LongtermDebtandFinanceLeasesSeniorNotesOutstandingwithEarlyRedemptionFeaturesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_8a402994-1ddc-44e7-924a-771a9dfe0dae" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_9a262850-ae4f-4f8e-aa18-d17bcc7fe329" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_8a402994-1ddc-44e7-924a-771a9dfe0dae" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_9a262850-ae4f-4f8e-aa18-d17bcc7fe329" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_83a03ea6-911a-44f6-8b02-0f2a53f4c3f7" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_8a402994-1ddc-44e7-924a-771a9dfe0dae" xlink:to="loc_us-gaap_DebtInstrumentTable_83a03ea6-911a-44f6-8b02-0f2a53f4c3f7" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_aeb9be6a-23a6-43bf-bf1c-08e8d9cba0c9" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_83a03ea6-911a-44f6-8b02-0f2a53f4c3f7" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_aeb9be6a-23a6-43bf-bf1c-08e8d9cba0c9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_aeb9be6a-23a6-43bf-bf1c-08e8d9cba0c9_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_aeb9be6a-23a6-43bf-bf1c-08e8d9cba0c9" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_aeb9be6a-23a6-43bf-bf1c-08e8d9cba0c9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_dad7975c-429f-48d9-a5fc-1bdbd5b324f9" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_aeb9be6a-23a6-43bf-bf1c-08e8d9cba0c9" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_dad7975c-429f-48d9-a5fc-1bdbd5b324f9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_RecourseDebtMember_316c19c4-bd69-4d76-a958-6d50403d9166" xlink:href="nrg-20201231.xsd#nrg_RecourseDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_dad7975c-429f-48d9-a5fc-1bdbd5b324f9" xlink:to="loc_nrg_RecourseDebtMember_316c19c4-bd69-4d76-a958-6d50403d9166" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_4b6b275b-5a1a-4125-bd20-560fcaa2aa17" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_83a03ea6-911a-44f6-8b02-0f2a53f4c3f7" xlink:to="loc_us-gaap_DebtInstrumentAxis_4b6b275b-5a1a-4125-bd20-560fcaa2aa17" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_4b6b275b-5a1a-4125-bd20-560fcaa2aa17_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_4b6b275b-5a1a-4125-bd20-560fcaa2aa17" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_4b6b275b-5a1a-4125-bd20-560fcaa2aa17_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_0d51456d-258f-4ef9-a0ce-2342222c14e3" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_4b6b275b-5a1a-4125-bd20-560fcaa2aa17" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_0d51456d-258f-4ef9-a0ce-2342222c14e3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_SeniorNotesdue2026Member_e0b1081b-4b02-40a0-8a69-9618ffb41193" xlink:href="nrg-20201231.xsd#nrg_SeniorNotesdue2026Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_0d51456d-258f-4ef9-a0ce-2342222c14e3" xlink:to="loc_nrg_SeniorNotesdue2026Member_e0b1081b-4b02-40a0-8a69-9618ffb41193" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_SeniorNotesdue2027Member_41a4e9fa-1d38-4f5c-870b-9fd0e7d32c78" xlink:href="nrg-20201231.xsd#nrg_SeniorNotesdue2027Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_0d51456d-258f-4ef9-a0ce-2342222c14e3" xlink:to="loc_nrg_SeniorNotesdue2027Member_41a4e9fa-1d38-4f5c-870b-9fd0e7d32c78" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_SeniorNotesdue2028Member_7c3fd641-b69b-46d5-917d-4c35a368b6d4" xlink:href="nrg-20201231.xsd#nrg_SeniorNotesdue2028Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_0d51456d-258f-4ef9-a0ce-2342222c14e3" xlink:to="loc_nrg_SeniorNotesdue2028Member_7c3fd641-b69b-46d5-917d-4c35a368b6d4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_A525SeniorNotesDue2029Member_bc31c57a-b950-418a-ab8d-ed6fe78da100" xlink:href="nrg-20201231.xsd#nrg_A525SeniorNotesDue2029Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_0d51456d-258f-4ef9-a0ce-2342222c14e3" xlink:to="loc_nrg_A525SeniorNotesDue2029Member_bc31c57a-b950-418a-ab8d-ed6fe78da100" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_A3375SeniorUnsecuredNotesDue2029Member_cbf4a9c0-6a25-4ae3-9231-2f0a58c04daf" xlink:href="nrg-20201231.xsd#nrg_A3375SeniorUnsecuredNotesDue2029Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_0d51456d-258f-4ef9-a0ce-2342222c14e3" xlink:to="loc_nrg_A3375SeniorUnsecuredNotesDue2029Member_cbf4a9c0-6a25-4ae3-9231-2f0a58c04daf" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_A3625SeniorUnsecuredNotesDueFebruary2031Member_6938407c-787c-4f55-8b53-e52fc8ffe5f5" xlink:href="nrg-20201231.xsd#nrg_A3625SeniorUnsecuredNotesDueFebruary2031Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_0d51456d-258f-4ef9-a0ce-2342222c14e3" xlink:to="loc_nrg_A3625SeniorUnsecuredNotesDueFebruary2031Member_6938407c-787c-4f55-8b53-e52fc8ffe5f5" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/LongtermDebtandFinanceLeasesRecourseDebtRedemptionPeriodDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#LongtermDebtandFinanceLeasesRecourseDebtRedemptionPeriodDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/LongtermDebtandFinanceLeasesRecourseDebtRedemptionPeriodDetails" xlink:type="extended" id="i8c5f042e0b304737a728017d643147c4_LongtermDebtandFinanceLeasesRecourseDebtRedemptionPeriodDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_2343cd44-703c-4778-84d6-a203ec68745f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPricePercentageOfPrincipalAmountRedeemed_b9935921-6d9e-45fd-8dcd-2354aaf2055f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentRedemptionPricePercentageOfPrincipalAmountRedeemed"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2343cd44-703c-4778-84d6-a203ec68745f" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPricePercentageOfPrincipalAmountRedeemed_b9935921-6d9e-45fd-8dcd-2354aaf2055f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPricePercentage_dba4fb7e-65ab-4b5a-aa2a-8529fabbb975" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentRedemptionPricePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2343cd44-703c-4778-84d6-a203ec68745f" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPricePercentage_dba4fb7e-65ab-4b5a-aa2a-8529fabbb975" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_DebtInstrumentOutstandingAmountAfterRedemptionPercentage_deff0a63-e02e-4f1d-b325-b46392edaa6e" xlink:href="nrg-20201231.xsd#nrg_DebtInstrumentOutstandingAmountAfterRedemptionPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2343cd44-703c-4778-84d6-a203ec68745f" xlink:to="loc_nrg_DebtInstrumentOutstandingAmountAfterRedemptionPercentage_deff0a63-e02e-4f1d-b325-b46392edaa6e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_PremiumPercentageOfPrincipalOfSeniorNotesDiscountFactor_f3b32234-6261-43ab-bf3e-64eff328d110" xlink:href="nrg-20201231.xsd#nrg_PremiumPercentageOfPrincipalOfSeniorNotesDiscountFactor"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2343cd44-703c-4778-84d6-a203ec68745f" xlink:to="loc_nrg_PremiumPercentageOfPrincipalOfSeniorNotesDiscountFactor_f3b32234-6261-43ab-bf3e-64eff328d110" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_DebtInstrumentPresentValueOfNoteRate_8a1d1697-cbc8-4804-ab13-85e14910ae27" xlink:href="nrg-20201231.xsd#nrg_DebtInstrumentPresentValueOfNoteRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2343cd44-703c-4778-84d6-a203ec68745f" xlink:to="loc_nrg_DebtInstrumentPresentValueOfNoteRate_8a1d1697-cbc8-4804-ab13-85e14910ae27" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_fb53cf1a-ba57-4bb6-b4dc-e7056e9bf202" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentBasisSpreadOnVariableRate1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2343cd44-703c-4778-84d6-a203ec68745f" xlink:to="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_fb53cf1a-ba57-4bb6-b4dc-e7056e9bf202" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_7d30703e-d87c-47f6-ad5a-63719348ab61" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2343cd44-703c-4778-84d6-a203ec68745f" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_7d30703e-d87c-47f6-ad5a-63719348ab61" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_c11612e3-5b6b-4eff-b7b6-9adb1231ee5a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2343cd44-703c-4778-84d6-a203ec68745f" xlink:to="loc_us-gaap_DebtInstrumentTable_c11612e3-5b6b-4eff-b7b6-9adb1231ee5a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_2edcd753-9144-4c38-9713-3ee15253de9d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_c11612e3-5b6b-4eff-b7b6-9adb1231ee5a" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_2edcd753-9144-4c38-9713-3ee15253de9d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_2edcd753-9144-4c38-9713-3ee15253de9d_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_2edcd753-9144-4c38-9713-3ee15253de9d" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_2edcd753-9144-4c38-9713-3ee15253de9d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_5565d67f-39e5-410d-9baa-e72539053839" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_2edcd753-9144-4c38-9713-3ee15253de9d" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_5565d67f-39e5-410d-9baa-e72539053839" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_RecourseDebtMember_8a980096-73cd-40c1-82d2-cdbd40c380d0" xlink:href="nrg-20201231.xsd#nrg_RecourseDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_5565d67f-39e5-410d-9baa-e72539053839" xlink:to="loc_nrg_RecourseDebtMember_8a980096-73cd-40c1-82d2-cdbd40c380d0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_90fdf4f2-b154-4026-82aa-ba51f3cb0d9f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_c11612e3-5b6b-4eff-b7b6-9adb1231ee5a" xlink:to="loc_us-gaap_DebtInstrumentAxis_90fdf4f2-b154-4026-82aa-ba51f3cb0d9f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_90fdf4f2-b154-4026-82aa-ba51f3cb0d9f_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_90fdf4f2-b154-4026-82aa-ba51f3cb0d9f" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_90fdf4f2-b154-4026-82aa-ba51f3cb0d9f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_1dd512d3-808b-4f77-b127-789e07c2bdc0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_90fdf4f2-b154-4026-82aa-ba51f3cb0d9f" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_1dd512d3-808b-4f77-b127-789e07c2bdc0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeniorNotesMember_79b32741-4805-4458-bb8c-e6ebfe58cc17" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SeniorNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_1dd512d3-808b-4f77-b127-789e07c2bdc0" xlink:to="loc_us-gaap_SeniorNotesMember_79b32741-4805-4458-bb8c-e6ebfe58cc17" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_SeniorNotesdue2026Member_cfe3f832-7137-46d9-80c3-bb51be2cce3e" xlink:href="nrg-20201231.xsd#nrg_SeniorNotesdue2026Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_1dd512d3-808b-4f77-b127-789e07c2bdc0" xlink:to="loc_nrg_SeniorNotesdue2026Member_cfe3f832-7137-46d9-80c3-bb51be2cce3e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_SeniorNotesdue2027Member_db58e73d-19db-473d-914a-823f28c90b9f" xlink:href="nrg-20201231.xsd#nrg_SeniorNotesdue2027Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_1dd512d3-808b-4f77-b127-789e07c2bdc0" xlink:to="loc_nrg_SeniorNotesdue2027Member_db58e73d-19db-473d-914a-823f28c90b9f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_SeniorNotesdue2028Member_2c298686-968d-401d-901a-b7cb9e7a175b" xlink:href="nrg-20201231.xsd#nrg_SeniorNotesdue2028Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_1dd512d3-808b-4f77-b127-789e07c2bdc0" xlink:to="loc_nrg_SeniorNotesdue2028Member_2c298686-968d-401d-901a-b7cb9e7a175b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_A525SeniorNotesDue2029Member_36c776b5-9109-479b-8fb6-c5fc09412230" xlink:href="nrg-20201231.xsd#nrg_A525SeniorNotesDue2029Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_1dd512d3-808b-4f77-b127-789e07c2bdc0" xlink:to="loc_nrg_A525SeniorNotesDue2029Member_36c776b5-9109-479b-8fb6-c5fc09412230" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_A3375SeniorUnsecuredNotesDue2029Member_fffea12d-6e7f-4cc7-873c-3f0d6fd2b27c" xlink:href="nrg-20201231.xsd#nrg_A3375SeniorUnsecuredNotesDue2029Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_1dd512d3-808b-4f77-b127-789e07c2bdc0" xlink:to="loc_nrg_A3375SeniorUnsecuredNotesDue2029Member_fffea12d-6e7f-4cc7-873c-3f0d6fd2b27c" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_A3625SeniorUnsecuredNotesDueFebruary2031Member_85a31448-d458-4169-a834-4b6c8d56068f" xlink:href="nrg-20201231.xsd#nrg_A3625SeniorUnsecuredNotesDueFebruary2031Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_1dd512d3-808b-4f77-b127-789e07c2bdc0" xlink:to="loc_nrg_A3625SeniorUnsecuredNotesDueFebruary2031Member_85a31448-d458-4169-a834-4b6c8d56068f" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateAxis_f1093506-8b21-4c23-ab43-31a451dd0efc" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_VariableRateAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_c11612e3-5b6b-4eff-b7b6-9adb1231ee5a" xlink:to="loc_us-gaap_VariableRateAxis_f1093506-8b21-4c23-ab43-31a451dd0efc" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain_f1093506-8b21-4c23-ab43-31a451dd0efc_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_VariableRateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_VariableRateAxis_f1093506-8b21-4c23-ab43-31a451dd0efc" xlink:to="loc_us-gaap_VariableRateDomain_f1093506-8b21-4c23-ab43-31a451dd0efc_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain_3bfc224f-02b9-488c-bb3e-ed560e7bccfd" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_VariableRateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_VariableRateAxis_f1093506-8b21-4c23-ab43-31a451dd0efc" xlink:to="loc_us-gaap_VariableRateDomain_3bfc224f-02b9-488c-bb3e-ed560e7bccfd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_TreasuryRateMember_119faa18-7cd1-45c4-acb6-905061c8aabf" xlink:href="nrg-20201231.xsd#nrg_TreasuryRateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_3bfc224f-02b9-488c-bb3e-ed560e7bccfd" xlink:to="loc_nrg_TreasuryRateMember_119faa18-7cd1-45c4-acb6-905061c8aabf" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_e8cdf466-9efc-4965-a3af-1ffda3d72023" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentRedemptionPeriodAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_c11612e3-5b6b-4eff-b7b6-9adb1231ee5a" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_e8cdf466-9efc-4965-a3af-1ffda3d72023" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_e8cdf466-9efc-4965-a3af-1ffda3d72023_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentRedemptionPeriodDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_e8cdf466-9efc-4965-a3af-1ffda3d72023" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_e8cdf466-9efc-4965-a3af-1ffda3d72023_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_b5133772-91e8-43c6-9d6d-1e2dd9435f98" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentRedemptionPeriodDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_e8cdf466-9efc-4965-a3af-1ffda3d72023" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_b5133772-91e8-43c6-9d6d-1e2dd9435f98" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_RedemptionPeriodPriorTo15May2021Member_a77b2c54-145e-448a-89c9-a6d3d95b9a6a" xlink:href="nrg-20201231.xsd#nrg_RedemptionPeriodPriorTo15May2021Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_b5133772-91e8-43c6-9d6d-1e2dd9435f98" xlink:to="loc_nrg_RedemptionPeriodPriorTo15May2021Member_a77b2c54-145e-448a-89c9-a6d3d95b9a6a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_RedemptionPeriodFrom15May2021to14May2022Member_e72d939a-0250-47b7-ab86-6783bfb25c85" xlink:href="nrg-20201231.xsd#nrg_RedemptionPeriodFrom15May2021to14May2022Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_b5133772-91e8-43c6-9d6d-1e2dd9435f98" xlink:to="loc_nrg_RedemptionPeriodFrom15May2021to14May2022Member_e72d939a-0250-47b7-ab86-6783bfb25c85" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_RedemptionPeriodFrom15May2022to14May2023Member_ece71a9a-7b18-4e01-8af1-895c87f7866e" xlink:href="nrg-20201231.xsd#nrg_RedemptionPeriodFrom15May2022to14May2023Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_b5133772-91e8-43c6-9d6d-1e2dd9435f98" xlink:to="loc_nrg_RedemptionPeriodFrom15May2022to14May2023Member_ece71a9a-7b18-4e01-8af1-895c87f7866e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_RedemptionPeriodFrom15May2023to14May2024Member_058a0022-fdfa-4b89-bbb4-707b9f184984" xlink:href="nrg-20201231.xsd#nrg_RedemptionPeriodFrom15May2023to14May2024Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_b5133772-91e8-43c6-9d6d-1e2dd9435f98" xlink:to="loc_nrg_RedemptionPeriodFrom15May2023to14May2024Member_058a0022-fdfa-4b89-bbb4-707b9f184984" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_RedemptionPeriodFrom15May2024AndThereafterMember_29cbfd5c-f78d-466c-9c97-cc19541e41ad" xlink:href="nrg-20201231.xsd#nrg_RedemptionPeriodFrom15May2024AndThereafterMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_b5133772-91e8-43c6-9d6d-1e2dd9435f98" xlink:to="loc_nrg_RedemptionPeriodFrom15May2024AndThereafterMember_29cbfd5c-f78d-466c-9c97-cc19541e41ad" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_RedemptionPeriodPriorTo15July2021Member_2c46d1b3-14b9-40d3-a15a-ec1a5a19adb9" xlink:href="nrg-20201231.xsd#nrg_RedemptionPeriodPriorTo15July2021Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_b5133772-91e8-43c6-9d6d-1e2dd9435f98" xlink:to="loc_nrg_RedemptionPeriodPriorTo15July2021Member_2c46d1b3-14b9-40d3-a15a-ec1a5a19adb9" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_RedemptionPeriodFrom15July2021to14July2022Member_442835d1-2b6d-481f-b401-7d9fc03add4d" xlink:href="nrg-20201231.xsd#nrg_RedemptionPeriodFrom15July2021to14July2022Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_b5133772-91e8-43c6-9d6d-1e2dd9435f98" xlink:to="loc_nrg_RedemptionPeriodFrom15July2021to14July2022Member_442835d1-2b6d-481f-b401-7d9fc03add4d" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_RedemptionPeriodFrom15July2022to14July2023Member_27029321-327b-4dd0-9cf8-aa7686616c90" xlink:href="nrg-20201231.xsd#nrg_RedemptionPeriodFrom15July2022to14July2023Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_b5133772-91e8-43c6-9d6d-1e2dd9435f98" xlink:to="loc_nrg_RedemptionPeriodFrom15July2022to14July2023Member_27029321-327b-4dd0-9cf8-aa7686616c90" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_RedemptionPeriodFrom15July2023to14July2024Member_b738ffca-f2d6-4143-99b2-c02a2118516d" xlink:href="nrg-20201231.xsd#nrg_RedemptionPeriodFrom15July2023to14July2024Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_b5133772-91e8-43c6-9d6d-1e2dd9435f98" xlink:to="loc_nrg_RedemptionPeriodFrom15July2023to14July2024Member_b738ffca-f2d6-4143-99b2-c02a2118516d" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_RedemptionPeriodFrom15July2024AndThereafterMember_ee8ca079-2a59-41b8-815f-055277db3ba8" xlink:href="nrg-20201231.xsd#nrg_RedemptionPeriodFrom15July2024AndThereafterMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_b5133772-91e8-43c6-9d6d-1e2dd9435f98" xlink:to="loc_nrg_RedemptionPeriodFrom15July2024AndThereafterMember_ee8ca079-2a59-41b8-815f-055277db3ba8" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_RedemptionPeriodPriortoJanuary152021Member_864977d0-2269-4f0e-9238-3eb9b97a079a" xlink:href="nrg-20201231.xsd#nrg_RedemptionPeriodPriortoJanuary152021Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_b5133772-91e8-43c6-9d6d-1e2dd9435f98" xlink:to="loc_nrg_RedemptionPeriodPriortoJanuary152021Member_864977d0-2269-4f0e-9238-3eb9b97a079a" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_RedemptionPeriodPriortoJanuary152023Member_12889ea2-6b4e-45bb-9105-d4a58db58f60" xlink:href="nrg-20201231.xsd#nrg_RedemptionPeriodPriortoJanuary152023Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_b5133772-91e8-43c6-9d6d-1e2dd9435f98" xlink:to="loc_nrg_RedemptionPeriodPriortoJanuary152023Member_12889ea2-6b4e-45bb-9105-d4a58db58f60" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_RedemptionPeriodFrom15January2023to14January2024Member_e443a42d-5112-4173-9500-da46d801ae37" xlink:href="nrg-20201231.xsd#nrg_RedemptionPeriodFrom15January2023to14January2024Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_b5133772-91e8-43c6-9d6d-1e2dd9435f98" xlink:to="loc_nrg_RedemptionPeriodFrom15January2023to14January2024Member_e443a42d-5112-4173-9500-da46d801ae37" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_RedemptionPeriodFrom15January2024to14January2025Member_c492dfa5-099a-439d-92de-0c4e5fe5a564" xlink:href="nrg-20201231.xsd#nrg_RedemptionPeriodFrom15January2024to14January2025Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_b5133772-91e8-43c6-9d6d-1e2dd9435f98" xlink:to="loc_nrg_RedemptionPeriodFrom15January2024to14January2025Member_c492dfa5-099a-439d-92de-0c4e5fe5a564" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_RedemptionPeriodFrom15January2025to14January2026Member_5f38c1ff-7851-4744-be19-2ba85e50e300" xlink:href="nrg-20201231.xsd#nrg_RedemptionPeriodFrom15January2025to14January2026Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_b5133772-91e8-43c6-9d6d-1e2dd9435f98" xlink:to="loc_nrg_RedemptionPeriodFrom15January2025to14January2026Member_5f38c1ff-7851-4744-be19-2ba85e50e300" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_RedemptionPeriodFrom15January2026AndThereafterMember_1dbacb1d-5a34-496c-88f7-bb51591b21d5" xlink:href="nrg-20201231.xsd#nrg_RedemptionPeriodFrom15January2026AndThereafterMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_b5133772-91e8-43c6-9d6d-1e2dd9435f98" xlink:to="loc_nrg_RedemptionPeriodFrom15January2026AndThereafterMember_1dbacb1d-5a34-496c-88f7-bb51591b21d5" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_RedemptionPeriodPriorToJune152022Member_0b87e8ff-4f8b-4683-94db-6da0927ff2cc" xlink:href="nrg-20201231.xsd#nrg_RedemptionPeriodPriorToJune152022Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_b5133772-91e8-43c6-9d6d-1e2dd9435f98" xlink:to="loc_nrg_RedemptionPeriodPriorToJune152022Member_0b87e8ff-4f8b-4683-94db-6da0927ff2cc" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_RedemptionPeriodPriorToJune152024Member_32459ac5-cf05-4a88-840e-3ffc1b41fa19" xlink:href="nrg-20201231.xsd#nrg_RedemptionPeriodPriorToJune152024Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_b5133772-91e8-43c6-9d6d-1e2dd9435f98" xlink:to="loc_nrg_RedemptionPeriodPriorToJune152024Member_32459ac5-cf05-4a88-840e-3ffc1b41fa19" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_RedemptionPeriodFrom15June2024To14June2025Member_862a9dc5-cd35-4d1b-9936-beff7b86bb0c" xlink:href="nrg-20201231.xsd#nrg_RedemptionPeriodFrom15June2024To14June2025Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_b5133772-91e8-43c6-9d6d-1e2dd9435f98" xlink:to="loc_nrg_RedemptionPeriodFrom15June2024To14June2025Member_862a9dc5-cd35-4d1b-9936-beff7b86bb0c" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_RedemptionPeriodFrom15June2025To14June2026Member_279aa0c1-58af-44ec-bff9-f3f736d740db" xlink:href="nrg-20201231.xsd#nrg_RedemptionPeriodFrom15June2025To14June2026Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_b5133772-91e8-43c6-9d6d-1e2dd9435f98" xlink:to="loc_nrg_RedemptionPeriodFrom15June2025To14June2026Member_279aa0c1-58af-44ec-bff9-f3f736d740db" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_RedemptionPeriodFrom15June2026To14June2027Member_0fa81650-6c6c-4ddf-adf5-0a1880551796" xlink:href="nrg-20201231.xsd#nrg_RedemptionPeriodFrom15June2026To14June2027Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_b5133772-91e8-43c6-9d6d-1e2dd9435f98" xlink:to="loc_nrg_RedemptionPeriodFrom15June2026To14June2027Member_0fa81650-6c6c-4ddf-adf5-0a1880551796" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_RedemptionPeriodFromJune152027AndThereafterMember_1f210094-0d3c-4764-a6e3-ad4592e96b5b" xlink:href="nrg-20201231.xsd#nrg_RedemptionPeriodFromJune152027AndThereafterMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_b5133772-91e8-43c6-9d6d-1e2dd9435f98" xlink:to="loc_nrg_RedemptionPeriodFromJune152027AndThereafterMember_1f210094-0d3c-4764-a6e3-ad4592e96b5b" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_RedemptionPeriodPriorToFebruary152024Member_bfc474c1-fa18-4ecd-a29f-74fb804f6e51" xlink:href="nrg-20201231.xsd#nrg_RedemptionPeriodPriorToFebruary152024Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_b5133772-91e8-43c6-9d6d-1e2dd9435f98" xlink:to="loc_nrg_RedemptionPeriodPriorToFebruary152024Member_bfc474c1-fa18-4ecd-a29f-74fb804f6e51" xlink:type="arc" order="22"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_RedemptionPeriodFebruary152024ToFebruary142025Member_361fb8c1-81e7-4020-8ce2-9e41bc4e58ff" xlink:href="nrg-20201231.xsd#nrg_RedemptionPeriodFebruary152024ToFebruary142025Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_b5133772-91e8-43c6-9d6d-1e2dd9435f98" xlink:to="loc_nrg_RedemptionPeriodFebruary152024ToFebruary142025Member_361fb8c1-81e7-4020-8ce2-9e41bc4e58ff" xlink:type="arc" order="23"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_RedemptionPeriodFebruary152025ToFebruary142026Member_6bc6fd1e-00aa-4f5f-a334-a4d065296492" xlink:href="nrg-20201231.xsd#nrg_RedemptionPeriodFebruary152025ToFebruary142026Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_b5133772-91e8-43c6-9d6d-1e2dd9435f98" xlink:to="loc_nrg_RedemptionPeriodFebruary152025ToFebruary142026Member_6bc6fd1e-00aa-4f5f-a334-a4d065296492" xlink:type="arc" order="24"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_RedemptionPeriodFebruary152026AndThereafterMember_dfb14249-7ceb-40d6-b20c-284fff440064" xlink:href="nrg-20201231.xsd#nrg_RedemptionPeriodFebruary152026AndThereafterMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_b5133772-91e8-43c6-9d6d-1e2dd9435f98" xlink:to="loc_nrg_RedemptionPeriodFebruary152026AndThereafterMember_dfb14249-7ceb-40d6-b20c-284fff440064" xlink:type="arc" order="25"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_RedemptionPeriodPriorToFebruary152026Member_1e681f35-32a2-467e-9841-1ea7c3d3c4f7" xlink:href="nrg-20201231.xsd#nrg_RedemptionPeriodPriorToFebruary152026Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_b5133772-91e8-43c6-9d6d-1e2dd9435f98" xlink:to="loc_nrg_RedemptionPeriodPriorToFebruary152026Member_1e681f35-32a2-467e-9841-1ea7c3d3c4f7" xlink:type="arc" order="26"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_RedemptionPeriodFebruary152026ToFebruary142027Member_c5c2578a-8bac-4130-87eb-c9c2b1e19ff8" xlink:href="nrg-20201231.xsd#nrg_RedemptionPeriodFebruary152026ToFebruary142027Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_b5133772-91e8-43c6-9d6d-1e2dd9435f98" xlink:to="loc_nrg_RedemptionPeriodFebruary152026ToFebruary142027Member_c5c2578a-8bac-4130-87eb-c9c2b1e19ff8" xlink:type="arc" order="27"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_RedemptionPeriodFebruary152027ToFebruary142028Member_0b9c499e-8621-4993-ba20-3d6942b57452" xlink:href="nrg-20201231.xsd#nrg_RedemptionPeriodFebruary152027ToFebruary142028Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_b5133772-91e8-43c6-9d6d-1e2dd9435f98" xlink:to="loc_nrg_RedemptionPeriodFebruary152027ToFebruary142028Member_0b9c499e-8621-4993-ba20-3d6942b57452" xlink:type="arc" order="28"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_RedemptionPeriodFebruary152028ToFebruary142029Member_3b3f4dcf-684f-465c-9217-fad748d0287c" xlink:href="nrg-20201231.xsd#nrg_RedemptionPeriodFebruary152028ToFebruary142029Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_b5133772-91e8-43c6-9d6d-1e2dd9435f98" xlink:to="loc_nrg_RedemptionPeriodFebruary152028ToFebruary142029Member_3b3f4dcf-684f-465c-9217-fad748d0287c" xlink:type="arc" order="29"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_RedemptionPeriodFebruary152029AndThereafterMember_983eb7d5-be50-4d16-a5a4-62123081281b" xlink:href="nrg-20201231.xsd#nrg_RedemptionPeriodFebruary152029AndThereafterMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_b5133772-91e8-43c6-9d6d-1e2dd9435f98" xlink:to="loc_nrg_RedemptionPeriodFebruary152029AndThereafterMember_983eb7d5-be50-4d16-a5a4-62123081281b" xlink:type="arc" order="30"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/LongtermDebtandFinanceLeasesSeniorCreditFacilityandTaxExemptBondsDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#LongtermDebtandFinanceLeasesSeniorCreditFacilityandTaxExemptBondsDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/LongtermDebtandFinanceLeasesSeniorCreditFacilityandTaxExemptBondsDetails" xlink:type="extended" id="i42feef72177e46a3bb1880a6961e7de5_LongtermDebtandFinanceLeasesSeniorCreditFacilityandTaxExemptBondsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_ccbc5305-a365-4dc5-a4c5-69d5d54dae68" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RepaymentsOfLongTermDebt_0e634dde-d5c2-4aab-a906-d33d00677d06" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RepaymentsOfLongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_ccbc5305-a365-4dc5-a4c5-69d5d54dae68" xlink:to="loc_us-gaap_RepaymentsOfLongTermDebt_0e634dde-d5c2-4aab-a906-d33d00677d06" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_IncreaseDecreaseInLongTermDebt_3dede0f0-d683-463a-8ede-87cbf70dde1f" xlink:href="nrg-20201231.xsd#nrg_IncreaseDecreaseInLongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_ccbc5305-a365-4dc5-a4c5-69d5d54dae68" xlink:to="loc_nrg_IncreaseDecreaseInLongTermDebt_3dede0f0-d683-463a-8ede-87cbf70dde1f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainsLossesOnExtinguishmentOfDebt_463ca3bc-b491-42a6-be9a-5aae6f929267" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GainsLossesOnExtinguishmentOfDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_ccbc5305-a365-4dc5-a4c5-69d5d54dae68" xlink:to="loc_us-gaap_GainsLossesOnExtinguishmentOfDebt_463ca3bc-b491-42a6-be9a-5aae6f929267" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WriteOffOfDeferredDebtIssuanceCost_eaf0338d-1074-40b1-acb6-4a748fc6b709" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_WriteOffOfDeferredDebtIssuanceCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_ccbc5305-a365-4dc5-a4c5-69d5d54dae68" xlink:to="loc_us-gaap_WriteOffOfDeferredDebtIssuanceCost_eaf0338d-1074-40b1-acb6-4a748fc6b709" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestIncomeExpenseNet_e07fb2d0-8918-4180-9d45-347a36256768" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InterestIncomeExpenseNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_ccbc5305-a365-4dc5-a4c5-69d5d54dae68" xlink:to="loc_us-gaap_InterestIncomeExpenseNet_e07fb2d0-8918-4180-9d45-347a36256768" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_LineOfCreditFacilityBorrowingCapacityIncrease_69626dcb-acf2-411f-a718-85684e790626" xlink:href="nrg-20201231.xsd#nrg_LineOfCreditFacilityBorrowingCapacityIncrease"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_ccbc5305-a365-4dc5-a4c5-69d5d54dae68" xlink:to="loc_nrg_LineOfCreditFacilityBorrowingCapacityIncrease_69626dcb-acf2-411f-a718-85684e790626" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_bcc376b7-ea2e-4d76-9cac-8bfde657bbf1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_ccbc5305-a365-4dc5-a4c5-69d5d54dae68" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_bcc376b7-ea2e-4d76-9cac-8bfde657bbf1" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_1e0d0019-5878-408f-8602-3041cedb3783" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentBasisSpreadOnVariableRate1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_ccbc5305-a365-4dc5-a4c5-69d5d54dae68" xlink:to="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_1e0d0019-5878-408f-8602-3041cedb3783" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_LineOfCreditFacilityMaximumBorrowingCapacityIncrease_eedd9cf2-ea16-40c4-980b-f89ef26498db" xlink:href="nrg-20201231.xsd#nrg_LineOfCreditFacilityMaximumBorrowingCapacityIncrease"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_ccbc5305-a365-4dc5-a4c5-69d5d54dae68" xlink:to="loc_nrg_LineOfCreditFacilityMaximumBorrowingCapacityIncrease_eedd9cf2-ea16-40c4-980b-f89ef26498db" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity_822d44b1-9c4e-46a0-b624-36a996abd46a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_ccbc5305-a365-4dc5-a4c5-69d5d54dae68" xlink:to="loc_us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity_822d44b1-9c4e-46a0-b624-36a996abd46a" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_LineOfCreditFacilityLienBasketMinimum_2ae873d6-b67e-4641-ab0b-72e4d94da515" xlink:href="nrg-20201231.xsd#nrg_LineOfCreditFacilityLienBasketMinimum"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_ccbc5305-a365-4dc5-a4c5-69d5d54dae68" xlink:to="loc_nrg_LineOfCreditFacilityLienBasketMinimum_2ae873d6-b67e-4641-ab0b-72e4d94da515" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_LineOfCreditFacilityLienBasketPercentageOfTotalAssets_03a33a91-3b81-47a3-aeed-211f128303fd" xlink:href="nrg-20201231.xsd#nrg_LineOfCreditFacilityLienBasketPercentageOfTotalAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_ccbc5305-a365-4dc5-a4c5-69d5d54dae68" xlink:to="loc_nrg_LineOfCreditFacilityLienBasketPercentageOfTotalAssets_03a33a91-3b81-47a3-aeed-211f128303fd" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_255814a2-b8ad-4c89-a928-657e7f3f1537" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_ccbc5305-a365-4dc5-a4c5-69d5d54dae68" xlink:to="loc_us-gaap_LongTermDebt_255814a2-b8ad-4c89-a928-657e7f3f1537" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_3ab1e22c-bcba-4cc5-9e56-055135fb060d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_ccbc5305-a365-4dc5-a4c5-69d5d54dae68" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_3ab1e22c-bcba-4cc5-9e56-055135fb060d" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_0577ead7-1d43-4aba-8167-1968f7a8f4ed" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_ccbc5305-a365-4dc5-a4c5-69d5d54dae68" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_0577ead7-1d43-4aba-8167-1968f7a8f4ed" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRepurchaseAmount_3634a396-d57b-4195-8996-af68aafa985b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentRepurchaseAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_ccbc5305-a365-4dc5-a4c5-69d5d54dae68" xlink:to="loc_us-gaap_DebtInstrumentRepurchaseAmount_3634a396-d57b-4195-8996-af68aafa985b" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_8338536d-3cd0-4fbe-8a56-2a9b654459cf" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_ccbc5305-a365-4dc5-a4c5-69d5d54dae68" xlink:to="loc_us-gaap_DebtInstrumentTable_8338536d-3cd0-4fbe-8a56-2a9b654459cf" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_092a092b-9291-4650-a4f4-3d1fd8cab585" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_8338536d-3cd0-4fbe-8a56-2a9b654459cf" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_092a092b-9291-4650-a4f4-3d1fd8cab585" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_092a092b-9291-4650-a4f4-3d1fd8cab585_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_092a092b-9291-4650-a4f4-3d1fd8cab585" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_092a092b-9291-4650-a4f4-3d1fd8cab585_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_4e3c7636-3d2c-4e5d-882f-904e1de31f83" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_092a092b-9291-4650-a4f4-3d1fd8cab585" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_4e3c7636-3d2c-4e5d-882f-904e1de31f83" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_RecourseDebtMember_a27eda2d-810a-40db-a1c1-19afb45cf46f" xlink:href="nrg-20201231.xsd#nrg_RecourseDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_4e3c7636-3d2c-4e5d-882f-904e1de31f83" xlink:to="loc_nrg_RecourseDebtMember_a27eda2d-810a-40db-a1c1-19afb45cf46f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_45a3e250-1004-42bb-a527-76038f0dc419" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_4e3c7636-3d2c-4e5d-882f-904e1de31f83" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_45a3e250-1004-42bb-a527-76038f0dc419" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_541dd5e2-eea0-4dc6-bfb5-17265a0fb9d5" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_4e3c7636-3d2c-4e5d-882f-904e1de31f83" xlink:to="loc_us-gaap_LineOfCreditMember_541dd5e2-eea0-4dc6-bfb5-17265a0fb9d5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredDebtMember_3c54cb51-3bc2-4dc5-a3a1-33ebe7265375" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_4e3c7636-3d2c-4e5d-882f-904e1de31f83" xlink:to="loc_us-gaap_SecuredDebtMember_3c54cb51-3bc2-4dc5-a3a1-33ebe7265375" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_NonRecourseDebtMember_77135aab-e325-4085-8fc3-0a5a778ff5d5" xlink:href="nrg-20201231.xsd#nrg_NonRecourseDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_4e3c7636-3d2c-4e5d-882f-904e1de31f83" xlink:to="loc_nrg_NonRecourseDebtMember_77135aab-e325-4085-8fc3-0a5a778ff5d5" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_a99ad081-2b4f-49b9-9082-2355ddaaba22" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_8338536d-3cd0-4fbe-8a56-2a9b654459cf" xlink:to="loc_us-gaap_DebtInstrumentAxis_a99ad081-2b4f-49b9-9082-2355ddaaba22" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_a99ad081-2b4f-49b9-9082-2355ddaaba22_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_a99ad081-2b4f-49b9-9082-2355ddaaba22" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_a99ad081-2b4f-49b9-9082-2355ddaaba22_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_c5e6667d-f687-43eb-a4ff-4ed243d69a77" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_a99ad081-2b4f-49b9-9082-2355ddaaba22" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_c5e6667d-f687-43eb-a4ff-4ed243d69a77" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_TermLoanFacilityDue2023Member_542036c9-ea85-4900-9afd-df5695c3ed83" xlink:href="nrg-20201231.xsd#nrg_TermLoanFacilityDue2023Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_c5e6667d-f687-43eb-a4ff-4ed243d69a77" xlink:to="loc_nrg_TermLoanFacilityDue2023Member_542036c9-ea85-4900-9afd-df5695c3ed83" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_CreditAgreementMember_7e8a7c00-376e-4a11-93fd-bb6d787f53d7" xlink:href="nrg-20201231.xsd#nrg_CreditAgreementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_c5e6667d-f687-43eb-a4ff-4ed243d69a77" xlink:to="loc_nrg_CreditAgreementMember_7e8a7c00-376e-4a11-93fd-bb6d787f53d7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_IndianRiverPower2020TaxExemptBondsDue2040Member_88afc0e7-a00c-41f5-b5b0-dcf3bf470d03" xlink:href="nrg-20201231.xsd#nrg_IndianRiverPower2020TaxExemptBondsDue2040Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_c5e6667d-f687-43eb-a4ff-4ed243d69a77" xlink:to="loc_nrg_IndianRiverPower2020TaxExemptBondsDue2040Member_88afc0e7-a00c-41f5-b5b0-dcf3bf470d03" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_IndianRiverPower2020TaxExemptBondsDue2045Member_985084f8-c43e-4cce-b6c9-2da127e6f67f" xlink:href="nrg-20201231.xsd#nrg_IndianRiverPower2020TaxExemptBondsDue2045Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_c5e6667d-f687-43eb-a4ff-4ed243d69a77" xlink:to="loc_nrg_IndianRiverPower2020TaxExemptBondsDue2045Member_985084f8-c43e-4cce-b6c9-2da127e6f67f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_IndianRiverPowerLlcTaxExemptBondsDue2040Member_f01d8803-9732-4710-8460-69c8d0dd0c9e" xlink:href="nrg-20201231.xsd#nrg_IndianRiverPowerLlcTaxExemptBondsDue2040Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_c5e6667d-f687-43eb-a4ff-4ed243d69a77" xlink:to="loc_nrg_IndianRiverPowerLlcTaxExemptBondsDue2040Member_f01d8803-9732-4710-8460-69c8d0dd0c9e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_IndianRiverPowerLlcTaxExemptBondsDue2045Member_f579c905-ca8e-4f53-bdae-09ff3c428e85" xlink:href="nrg-20201231.xsd#nrg_IndianRiverPowerLlcTaxExemptBondsDue2045Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_c5e6667d-f687-43eb-a4ff-4ed243d69a77" xlink:to="loc_nrg_IndianRiverPowerLlcTaxExemptBondsDue2045Member_f579c905-ca8e-4f53-bdae-09ff3c428e85" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_NRGDunkirk2020TaxExemptBondsDue2042Member_ce92fc65-2021-44fa-9ce3-7d92efe88597" xlink:href="nrg-20201231.xsd#nrg_NRGDunkirk2020TaxExemptBondsDue2042Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_c5e6667d-f687-43eb-a4ff-4ed243d69a77" xlink:to="loc_nrg_NRGDunkirk2020TaxExemptBondsDue2042Member_ce92fc65-2021-44fa-9ce3-7d92efe88597" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_DunkirkPowerLlcTaxExemptBondsDue2042Member_da6d2b3d-af01-4c56-84ad-3b07d83fe0a4" xlink:href="nrg-20201231.xsd#nrg_DunkirkPowerLlcTaxExemptBondsDue2042Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_c5e6667d-f687-43eb-a4ff-4ed243d69a77" xlink:to="loc_nrg_DunkirkPowerLlcTaxExemptBondsDue2042Member_da6d2b3d-af01-4c56-84ad-3b07d83fe0a4" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_FortBendCountytaxexemptbondsdue2045Member_4bda8d95-ff04-4c5b-ae46-5b61daff826c" xlink:href="nrg-20201231.xsd#nrg_FortBendCountytaxexemptbondsdue2045Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_c5e6667d-f687-43eb-a4ff-4ed243d69a77" xlink:to="loc_nrg_FortBendCountytaxexemptbondsdue2045Member_4bda8d95-ff04-4c5b-ae46-5b61daff826c" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_FortBendCountytaxexemptbondsdue2038Member_5b5f0d53-c0ed-465a-a6e3-a0382618c1af" xlink:href="nrg-20201231.xsd#nrg_FortBendCountytaxexemptbondsdue2038Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_c5e6667d-f687-43eb-a4ff-4ed243d69a77" xlink:to="loc_nrg_FortBendCountytaxexemptbondsdue2038Member_5b5f0d53-c0ed-465a-a6e3-a0382618c1af" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_FortBendCountytaxexemptbondsdue2042Member_01f7d632-615b-4309-a639-1e7bad446504" xlink:href="nrg-20201231.xsd#nrg_FortBendCountytaxexemptbondsdue2042Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_c5e6667d-f687-43eb-a4ff-4ed243d69a77" xlink:to="loc_nrg_FortBendCountytaxexemptbondsdue2042Member_01f7d632-615b-4309-a639-1e7bad446504" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_TaxexemptBondsMember_220cf785-9abd-48bf-8d31-8fed6c5a0d28" xlink:href="nrg-20201231.xsd#nrg_TaxexemptBondsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_c5e6667d-f687-43eb-a4ff-4ed243d69a77" xlink:to="loc_nrg_TaxexemptBondsMember_220cf785-9abd-48bf-8d31-8fed6c5a0d28" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_5232c006-7ba1-4faa-b579-ce7ae19bba09" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_8338536d-3cd0-4fbe-8a56-2a9b654459cf" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_5232c006-7ba1-4faa-b579-ce7ae19bba09" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_5232c006-7ba1-4faa-b579-ce7ae19bba09_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_5232c006-7ba1-4faa-b579-ce7ae19bba09" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_5232c006-7ba1-4faa-b579-ce7ae19bba09_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_7027f74e-c4f5-4df9-8c2a-26de062f44af" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_5232c006-7ba1-4faa-b579-ce7ae19bba09" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_7027f74e-c4f5-4df9-8c2a-26de062f44af" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateSwapMember_97fbae16-a119-49ef-8aca-8cab13160e44" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InterestRateSwapMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_7027f74e-c4f5-4df9-8c2a-26de062f44af" xlink:to="loc_us-gaap_InterestRateSwapMember_97fbae16-a119-49ef-8aca-8cab13160e44" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_82c14a2f-324f-4839-86e6-b1eb91f1ff1c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_8338536d-3cd0-4fbe-8a56-2a9b654459cf" xlink:to="loc_us-gaap_CreditFacilityAxis_82c14a2f-324f-4839-86e6-b1eb91f1ff1c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_82c14a2f-324f-4839-86e6-b1eb91f1ff1c_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_82c14a2f-324f-4839-86e6-b1eb91f1ff1c" xlink:to="loc_us-gaap_CreditFacilityDomain_82c14a2f-324f-4839-86e6-b1eb91f1ff1c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_5980a94c-4848-413e-937c-2b7220a811e5" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_82c14a2f-324f-4839-86e6-b1eb91f1ff1c" xlink:to="loc_us-gaap_CreditFacilityDomain_5980a94c-4848-413e-937c-2b7220a811e5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_0c4dddea-9ea6-4912-bc97-05a4b64eb219" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_5980a94c-4848-413e-937c-2b7220a811e5" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_0c4dddea-9ea6-4912-bc97-05a4b64eb219" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BridgeLoanMember_5be9cb8b-1e34-47d1-b922-2e9e3cff2eff" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BridgeLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_5980a94c-4848-413e-937c-2b7220a811e5" xlink:to="loc_us-gaap_BridgeLoanMember_5be9cb8b-1e34-47d1-b922-2e9e3cff2eff" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_DebtBasketMember_cd04c871-81c3-4225-a5c4-180154c355b2" xlink:href="nrg-20201231.xsd#nrg_DebtBasketMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_5980a94c-4848-413e-937c-2b7220a811e5" xlink:to="loc_nrg_DebtBasketMember_cd04c871-81c3-4225-a5c4-180154c355b2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateAxis_e526e679-6c4b-4371-81ac-759a13ae1bfd" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_VariableRateAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_8338536d-3cd0-4fbe-8a56-2a9b654459cf" xlink:to="loc_us-gaap_VariableRateAxis_e526e679-6c4b-4371-81ac-759a13ae1bfd" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain_e526e679-6c4b-4371-81ac-759a13ae1bfd_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_VariableRateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_VariableRateAxis_e526e679-6c4b-4371-81ac-759a13ae1bfd" xlink:to="loc_us-gaap_VariableRateDomain_e526e679-6c4b-4371-81ac-759a13ae1bfd_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain_f1d8a194-1994-4af7-af3b-2fcd5fa6a2c7" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_VariableRateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_VariableRateAxis_e526e679-6c4b-4371-81ac-759a13ae1bfd" xlink:to="loc_us-gaap_VariableRateDomain_f1d8a194-1994-4af7-af3b-2fcd5fa6a2c7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LondonInterbankOfferedRateLIBORMember_40b17568-934a-427b-a4b0-db794f11fd66" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LondonInterbankOfferedRateLIBORMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_f1d8a194-1994-4af7-af3b-2fcd5fa6a2c7" xlink:to="loc_us-gaap_LondonInterbankOfferedRateLIBORMember_40b17568-934a-427b-a4b0-db794f11fd66" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_AdjustedBaseRateMember_4080dec2-00ad-4b8b-836f-03dc36dfcd5a" xlink:href="nrg-20201231.xsd#nrg_AdjustedBaseRateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_f1d8a194-1994-4af7-af3b-2fcd5fa6a2c7" xlink:to="loc_nrg_AdjustedBaseRateMember_4080dec2-00ad-4b8b-836f-03dc36dfcd5a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_EurodollarApplicableMarginRateMember_e519ee93-17fa-499b-b4dc-359133985718" xlink:href="nrg-20201231.xsd#nrg_EurodollarApplicableMarginRateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_f1d8a194-1994-4af7-af3b-2fcd5fa6a2c7" xlink:to="loc_nrg_EurodollarApplicableMarginRateMember_e519ee93-17fa-499b-b4dc-359133985718" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_fa5e512f-631c-45a7-af77-c62c8e8e5957" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_8338536d-3cd0-4fbe-8a56-2a9b654459cf" xlink:to="loc_srt_RangeAxis_fa5e512f-631c-45a7-af77-c62c8e8e5957" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_fa5e512f-631c-45a7-af77-c62c8e8e5957_default" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_fa5e512f-631c-45a7-af77-c62c8e8e5957" xlink:to="loc_srt_RangeMember_fa5e512f-631c-45a7-af77-c62c8e8e5957_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_e1c93813-71ed-4aa4-8c04-3c58c0cd0190" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_fa5e512f-631c-45a7-af77-c62c8e8e5957" xlink:to="loc_srt_RangeMember_e1c93813-71ed-4aa4-8c04-3c58c0cd0190" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_b42346dc-1289-4325-bb50-da19f63b0481" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_e1c93813-71ed-4aa4-8c04-3c58c0cd0190" xlink:to="loc_srt_MinimumMember_b42346dc-1289-4325-bb50-da19f63b0481" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_bb241904-f7b1-4116-97c8-4fe92f409780" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_e1c93813-71ed-4aa4-8c04-3c58c0cd0190" xlink:to="loc_srt_MaximumMember_bb241904-f7b1-4116-97c8-4fe92f409780" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_6e1f534f-4622-4368-8e1e-5921a1ee2ef3" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_8338536d-3cd0-4fbe-8a56-2a9b654459cf" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_6e1f534f-4622-4368-8e1e-5921a1ee2ef3" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_6e1f534f-4622-4368-8e1e-5921a1ee2ef3_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_6e1f534f-4622-4368-8e1e-5921a1ee2ef3" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_6e1f534f-4622-4368-8e1e-5921a1ee2ef3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_22032b8d-41df-4490-89cb-1e68748bb6b0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_6e1f534f-4622-4368-8e1e-5921a1ee2ef3" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_22032b8d-41df-4490-89cb-1e68748bb6b0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_1ad56267-248d-4aff-9ca8-a1c844774662" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_22032b8d-41df-4490-89cb-1e68748bb6b0" xlink:to="loc_us-gaap_SubsequentEventMember_1ad56267-248d-4aff-9ca8-a1c844774662" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/LongtermDebtandFinanceLeasesNonRecourseDebtDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#LongtermDebtandFinanceLeasesNonRecourseDebtDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/LongtermDebtandFinanceLeasesNonRecourseDebtDetails" xlink:type="extended" id="idf0dbbd8a12a4d51ae2aae4e32b1fb30_LongtermDebtandFinanceLeasesNonRecourseDebtDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_2ce51b5f-049b-47c6-aa1a-ca58b4c34c9f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_9d4146cb-1728-419e-ad27-b70dbf10fada" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2ce51b5f-049b-47c6-aa1a-ca58b4c34c9f" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_9d4146cb-1728-419e-ad27-b70dbf10fada" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityCommitmentFeePercentage_0784e7b9-7806-4332-b816-c66657a5b234" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LineOfCreditFacilityCommitmentFeePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2ce51b5f-049b-47c6-aa1a-ca58b4c34c9f" xlink:to="loc_us-gaap_LineOfCreditFacilityCommitmentFeePercentage_0784e7b9-7806-4332-b816-c66657a5b234" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LettersOfCreditOutstandingAmount_67d10676-b0d4-4147-80c3-a3f7ff14b823" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LettersOfCreditOutstandingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2ce51b5f-049b-47c6-aa1a-ca58b4c34c9f" xlink:to="loc_us-gaap_LettersOfCreditOutstandingAmount_67d10676-b0d4-4147-80c3-a3f7ff14b823" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_890a99af-a721-41bf-8e67-9be1634a5f3c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2ce51b5f-049b-47c6-aa1a-ca58b4c34c9f" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_890a99af-a721-41bf-8e67-9be1634a5f3c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_PutOptionAgreementTerm_151b11f6-1841-4eca-9513-743a63b093c3" xlink:href="nrg-20201231.xsd#nrg_PutOptionAgreementTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2ce51b5f-049b-47c6-aa1a-ca58b4c34c9f" xlink:to="loc_nrg_PutOptionAgreementTerm_151b11f6-1841-4eca-9513-743a63b093c3" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeNotionalAmount_13c6e2f2-0bb7-45b7-b4c7-408df1ae4984" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeNotionalAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2ce51b5f-049b-47c6-aa1a-ca58b4c34c9f" xlink:to="loc_us-gaap_DerivativeNotionalAmount_13c6e2f2-0bb7-45b7-b4c7-408df1ae4984" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_f88afb3a-783c-49a9-ac5b-b464a40ee88f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2ce51b5f-049b-47c6-aa1a-ca58b4c34c9f" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_f88afb3a-783c-49a9-ac5b-b464a40ee88f" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_PutOptionAgreementSemiAnnualInterestRate_4de496d4-d1c2-4248-a280-c41a76557d52" xlink:href="nrg-20201231.xsd#nrg_PutOptionAgreementSemiAnnualInterestRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2ce51b5f-049b-47c6-aa1a-ca58b4c34c9f" xlink:to="loc_nrg_PutOptionAgreementSemiAnnualInterestRate_4de496d4-d1c2-4248-a280-c41a76557d52" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_PutOptionAgreementCovenantMandatoryExerciseOfIssuanceRightConsolidatedStockholdersEquityMinimum_3b0d33ed-2ded-4487-92e8-5342c6c31668" xlink:href="nrg-20201231.xsd#nrg_PutOptionAgreementCovenantMandatoryExerciseOfIssuanceRightConsolidatedStockholdersEquityMinimum"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2ce51b5f-049b-47c6-aa1a-ca58b4c34c9f" xlink:to="loc_nrg_PutOptionAgreementCovenantMandatoryExerciseOfIssuanceRightConsolidatedStockholdersEquityMinimum_3b0d33ed-2ded-4487-92e8-5342c6c31668" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPricePercentageOfPrincipalAmountRedeemed_4dc18248-f5f3-4b82-9584-372eb5d646c5" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentRedemptionPricePercentageOfPrincipalAmountRedeemed"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2ce51b5f-049b-47c6-aa1a-ca58b4c34c9f" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPricePercentageOfPrincipalAmountRedeemed_4dc18248-f5f3-4b82-9584-372eb5d646c5" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RepaymentsOfLongTermDebt_e58a91c5-277d-4202-b7d3-3c99d767706b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RepaymentsOfLongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2ce51b5f-049b-47c6-aa1a-ca58b4c34c9f" xlink:to="loc_us-gaap_RepaymentsOfLongTermDebt_e58a91c5-277d-4202-b7d3-3c99d767706b" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_3b75c921-ac6f-4faa-a58a-9c5d24111988" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2ce51b5f-049b-47c6-aa1a-ca58b4c34c9f" xlink:to="loc_us-gaap_DebtInstrumentTable_3b75c921-ac6f-4faa-a58a-9c5d24111988" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_ccd70c17-1973-457c-8a78-07f553f58f54" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_3b75c921-ac6f-4faa-a58a-9c5d24111988" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_ccd70c17-1973-457c-8a78-07f553f58f54" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_ccd70c17-1973-457c-8a78-07f553f58f54_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_ccd70c17-1973-457c-8a78-07f553f58f54" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_ccd70c17-1973-457c-8a78-07f553f58f54_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_5ec379ff-af31-46dc-9ad8-23e1d3c28a31" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_ccd70c17-1973-457c-8a78-07f553f58f54" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_5ec379ff-af31-46dc-9ad8-23e1d3c28a31" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_NonRecourseDebtMember_385cab88-a62d-4e20-b028-39a52187925d" xlink:href="nrg-20201231.xsd#nrg_NonRecourseDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_5ec379ff-af31-46dc-9ad8-23e1d3c28a31" xlink:to="loc_nrg_NonRecourseDebtMember_385cab88-a62d-4e20-b028-39a52187925d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_fe64db6f-aacb-4633-b2a3-7363b321a3ca" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_3b75c921-ac6f-4faa-a58a-9c5d24111988" xlink:to="loc_us-gaap_CreditFacilityAxis_fe64db6f-aacb-4633-b2a3-7363b321a3ca" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_fe64db6f-aacb-4633-b2a3-7363b321a3ca_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_fe64db6f-aacb-4633-b2a3-7363b321a3ca" xlink:to="loc_us-gaap_CreditFacilityDomain_fe64db6f-aacb-4633-b2a3-7363b321a3ca_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_e50a5b74-a295-4bc1-be30-d44b6dffc1ed" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_fe64db6f-aacb-4633-b2a3-7363b321a3ca" xlink:to="loc_us-gaap_CreditFacilityDomain_e50a5b74-a295-4bc1-be30-d44b6dffc1ed" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LetterOfCreditMember_418a6fd1-3a34-462e-b4c3-7b5de4c79168" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LetterOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_e50a5b74-a295-4bc1-be30-d44b6dffc1ed" xlink:to="loc_us-gaap_LetterOfCreditMember_418a6fd1-3a34-462e-b4c3-7b5de4c79168" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_3cf7af4b-b676-45f7-833e-a79b751bfb2b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_3b75c921-ac6f-4faa-a58a-9c5d24111988" xlink:to="loc_us-gaap_DebtInstrumentAxis_3cf7af4b-b676-45f7-833e-a79b751bfb2b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_3cf7af4b-b676-45f7-833e-a79b751bfb2b_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_3cf7af4b-b676-45f7-833e-a79b751bfb2b" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_3cf7af4b-b676-45f7-833e-a79b751bfb2b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_bb1d58d6-769f-4604-a1d1-52440d4927ae" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_3cf7af4b-b676-45f7-833e-a79b751bfb2b" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_bb1d58d6-769f-4604-a1d1-52440d4927ae" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_CreditAgreement2019Member_458deed9-670e-4208-8809-30bce13c424e" xlink:href="nrg-20201231.xsd#nrg_CreditAgreement2019Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_bb1d58d6-769f-4604-a1d1-52440d4927ae" xlink:to="loc_nrg_CreditAgreement2019Member_458deed9-670e-4208-8809-30bce13c424e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_BilateralLetterOfCreditFacilitiesMember_0b5c24ad-5b73-4292-9526-0a8db49fa524" xlink:href="nrg-20201231.xsd#nrg_BilateralLetterOfCreditFacilitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_bb1d58d6-769f-4604-a1d1-52440d4927ae" xlink:to="loc_nrg_BilateralLetterOfCreditFacilitiesMember_0b5c24ad-5b73-4292-9526-0a8db49fa524" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_A1841SeniorSecuredFirstLienNotesDue2023Member_b5a6b2ab-9ca4-453b-a268-0f015f24a68b" xlink:href="nrg-20201231.xsd#nrg_A1841SeniorSecuredFirstLienNotesDue2023Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_bb1d58d6-769f-4604-a1d1-52440d4927ae" xlink:to="loc_nrg_A1841SeniorSecuredFirstLienNotesDue2023Member_b5a6b2ab-9ca4-453b-a268-0f015f24a68b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_LetterOfCreditAgreementMember_1f6ad568-e924-40bc-9144-fa62f94c43fe" xlink:href="nrg-20201231.xsd#nrg_LetterOfCreditAgreementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_bb1d58d6-769f-4604-a1d1-52440d4927ae" xlink:to="loc_nrg_LetterOfCreditAgreementMember_1f6ad568-e924-40bc-9144-fa62f94c43fe" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_AguaCalienteBorrower1due2038Member_ba85d2f1-c3f2-455a-a025-66f093aab7db" xlink:href="nrg-20201231.xsd#nrg_AguaCalienteBorrower1due2038Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_bb1d58d6-769f-4604-a1d1-52440d4927ae" xlink:to="loc_nrg_AguaCalienteBorrower1due2038Member_ba85d2f1-c3f2-455a-a025-66f093aab7db" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_c76022a1-d864-4d9a-aa4d-9ab5df8f9c98" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_3b75c921-ac6f-4faa-a58a-9c5d24111988" xlink:to="loc_us-gaap_FinancialInstrumentAxis_c76022a1-d864-4d9a-aa4d-9ab5df8f9c98" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_c76022a1-d864-4d9a-aa4d-9ab5df8f9c98_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_c76022a1-d864-4d9a-aa4d-9ab5df8f9c98" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_c76022a1-d864-4d9a-aa4d-9ab5df8f9c98_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_ee8ee0cb-d1ef-42e0-8166-c24cce5e26ed" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_c76022a1-d864-4d9a-aa4d-9ab5df8f9c98" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_ee8ee0cb-d1ef-42e0-8166-c24cce5e26ed" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_PreCapitalizedTrustSecuritiesMember_7dc8eab6-d74a-426f-b5cf-c167f10f6159" xlink:href="nrg-20201231.xsd#nrg_PreCapitalizedTrustSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_ee8ee0cb-d1ef-42e0-8166-c24cce5e26ed" xlink:to="loc_nrg_PreCapitalizedTrustSecuritiesMember_7dc8eab6-d74a-426f-b5cf-c167f10f6159" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CounterpartyNameAxis_89dc5138-0351-46c6-9d1c-3f8a0ca60e9b" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_CounterpartyNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_3b75c921-ac6f-4faa-a58a-9c5d24111988" xlink:to="loc_srt_CounterpartyNameAxis_89dc5138-0351-46c6-9d1c-3f8a0ca60e9b" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_89dc5138-0351-46c6-9d1c-3f8a0ca60e9b_default" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CounterpartyNameAxis_89dc5138-0351-46c6-9d1c-3f8a0ca60e9b" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_89dc5138-0351-46c6-9d1c-3f8a0ca60e9b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_b9a85985-5087-4f1c-a65e-f305eb5b7aaf" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CounterpartyNameAxis_89dc5138-0351-46c6-9d1c-3f8a0ca60e9b" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_b9a85985-5087-4f1c-a65e-f305eb5b7aaf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_DelawareTrustMember_44903275-e765-48d0-a8bd-c35971cf6b9e" xlink:href="nrg-20201231.xsd#nrg_DelawareTrustMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_b9a85985-5087-4f1c-a65e-f305eb5b7aaf" xlink:to="loc_nrg_DelawareTrustMember_44903275-e765-48d0-a8bd-c35971cf6b9e" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/AssetRetirementObligations" xlink:type="simple" xlink:href="nrg-20201231.xsd#AssetRetirementObligations"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/AssetRetirementObligations" xlink:type="extended" id="i8859b4554a7146faa10e97da6ded7afe_AssetRetirementObligations"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/AssetRetirementObligationsTables" xlink:type="simple" xlink:href="nrg-20201231.xsd#AssetRetirementObligationsTables"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/AssetRetirementObligationsTables" xlink:type="extended" id="i68a347239ef44ce78fff9ac3ff21e46d_AssetRetirementObligationsTables"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/AssetRetirementObligationsDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#AssetRetirementObligationsDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/AssetRetirementObligationsDetails" xlink:type="extended" id="ibad33e512aec4f67a5818d06a42fd9fd_AssetRetirementObligationsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_nrg_AssetRetirementObligationsLineItems_b5455aa3-f8d0-4b65-b2fe-fb4c7031a9a5" xlink:href="nrg-20201231.xsd#nrg_AssetRetirementObligationsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetRetirementObligationRollForwardAnalysisRollForward_923e0de2-dca5-4033-81b8-12cec5a4e997" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AssetRetirementObligationRollForwardAnalysisRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_AssetRetirementObligationsLineItems_b5455aa3-f8d0-4b65-b2fe-fb4c7031a9a5" xlink:to="loc_us-gaap_AssetRetirementObligationRollForwardAnalysisRollForward_923e0de2-dca5-4033-81b8-12cec5a4e997" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetRetirementObligation_bc5266a2-93d4-464a-9dce-b78baf696fb1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AssetRetirementObligation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetRetirementObligationRollForwardAnalysisRollForward_923e0de2-dca5-4033-81b8-12cec5a4e997" xlink:to="loc_us-gaap_AssetRetirementObligation_bc5266a2-93d4-464a-9dce-b78baf696fb1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetRetirementObligationRevisionOfEstimate_8a7d1fe8-e561-4bf4-b813-72591f59d1ec" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AssetRetirementObligationRevisionOfEstimate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetRetirementObligationRollForwardAnalysisRollForward_923e0de2-dca5-4033-81b8-12cec5a4e997" xlink:to="loc_us-gaap_AssetRetirementObligationRevisionOfEstimate_8a7d1fe8-e561-4bf4-b813-72591f59d1ec" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostsIncurredAssetRetirementObligationIncurred_6283574c-84af-4b80-9231-aa6e70c4f26b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CostsIncurredAssetRetirementObligationIncurred"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetRetirementObligationRollForwardAnalysisRollForward_923e0de2-dca5-4033-81b8-12cec5a4e997" xlink:to="loc_us-gaap_CostsIncurredAssetRetirementObligationIncurred_6283574c-84af-4b80-9231-aa6e70c4f26b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetRetirementObligationLiabilitiesSettled_3f9716b1-f19e-48df-9129-b351d24ccc22" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AssetRetirementObligationLiabilitiesSettled"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetRetirementObligationRollForwardAnalysisRollForward_923e0de2-dca5-4033-81b8-12cec5a4e997" xlink:to="loc_us-gaap_AssetRetirementObligationLiabilitiesSettled_3f9716b1-f19e-48df-9129-b351d24ccc22" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetRetirementObligationAccretionExpense_b196d5a0-df69-4070-ae61-7fbb9acb3ffb" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AssetRetirementObligationAccretionExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetRetirementObligationRollForwardAnalysisRollForward_923e0de2-dca5-4033-81b8-12cec5a4e997" xlink:to="loc_us-gaap_AssetRetirementObligationAccretionExpense_b196d5a0-df69-4070-ae61-7fbb9acb3ffb" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetRetirementObligation_cf124bc3-d696-41b3-a887-daa03dcb42f1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AssetRetirementObligation"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_AssetRetirementObligationTable_34e73b9c-c466-42cb-aa5f-1ce092620cf8" xlink:href="nrg-20201231.xsd#nrg_AssetRetirementObligationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_nrg_AssetRetirementObligationsLineItems_b5455aa3-f8d0-4b65-b2fe-fb4c7031a9a5" xlink:to="loc_nrg_AssetRetirementObligationTable_34e73b9c-c466-42cb-aa5f-1ce092620cf8" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_AssetRetirementObligationsAxis_f55a2e77-3b83-4be9-8dc6-11892ca75d61" xlink:href="nrg-20201231.xsd#nrg_AssetRetirementObligationsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_nrg_AssetRetirementObligationTable_34e73b9c-c466-42cb-aa5f-1ce092620cf8" xlink:to="loc_nrg_AssetRetirementObligationsAxis_f55a2e77-3b83-4be9-8dc6-11892ca75d61" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_AssetRetirementObligationsDomain_f55a2e77-3b83-4be9-8dc6-11892ca75d61_default" xlink:href="nrg-20201231.xsd#nrg_AssetRetirementObligationsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_nrg_AssetRetirementObligationsAxis_f55a2e77-3b83-4be9-8dc6-11892ca75d61" xlink:to="loc_nrg_AssetRetirementObligationsDomain_f55a2e77-3b83-4be9-8dc6-11892ca75d61_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_AssetRetirementObligationsDomain_3c565310-2e62-44f3-9854-316735c01622" xlink:href="nrg-20201231.xsd#nrg_AssetRetirementObligationsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_nrg_AssetRetirementObligationsAxis_f55a2e77-3b83-4be9-8dc6-11892ca75d61" xlink:to="loc_nrg_AssetRetirementObligationsDomain_3c565310-2e62-44f3-9854-316735c01622" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_NuclearDecommissionMember_d45f0c6d-9484-47e3-ad61-1063d24ad465" xlink:href="nrg-20201231.xsd#nrg_NuclearDecommissionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_AssetRetirementObligationsDomain_3c565310-2e62-44f3-9854-316735c01622" xlink:to="loc_nrg_NuclearDecommissionMember_d45f0c6d-9484-47e3-ad61-1063d24ad465" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_OtherAssetRetirementObligationsMember_44e086f1-44e7-44c5-ac76-b8b260491278" xlink:href="nrg-20201231.xsd#nrg_OtherAssetRetirementObligationsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_AssetRetirementObligationsDomain_3c565310-2e62-44f3-9854-316735c01622" xlink:to="loc_nrg_OtherAssetRetirementObligationsMember_44e086f1-44e7-44c5-ac76-b8b260491278" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/BenefitPlansandOtherPostretirementBenefits" xlink:type="simple" xlink:href="nrg-20201231.xsd#BenefitPlansandOtherPostretirementBenefits"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/BenefitPlansandOtherPostretirementBenefits" xlink:type="extended" id="ia28496e616d744feb0a448574b016803_BenefitPlansandOtherPostretirementBenefits"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/BenefitPlansandOtherPostretirementBenefitsTables" xlink:type="simple" xlink:href="nrg-20201231.xsd#BenefitPlansandOtherPostretirementBenefitsTables"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/BenefitPlansandOtherPostretirementBenefitsTables" xlink:type="extended" id="i126dfc368e234957bf328899627c77aa_BenefitPlansandOtherPostretirementBenefitsTables"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/BenefitPlansandOtherPostretirementBenefitsNarrativeDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#BenefitPlansandOtherPostretirementBenefitsNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/BenefitPlansandOtherPostretirementBenefitsNarrativeDetails" xlink:type="extended" id="i90ae36e431334c5aa35fc85d02b7e3a0_BenefitPlansandOtherPostretirementBenefitsNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_0c5a4cc1-5de2-4ddb-90ef-ee80ff7948d1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanDisclosureLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_NumberOfDefinedBenefitPlans_17bbd09f-2990-45d2-86da-c7859ee5fd04" xlink:href="nrg-20201231.xsd#nrg_NumberOfDefinedBenefitPlans"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_0c5a4cc1-5de2-4ddb-90ef-ee80ff7948d1" xlink:to="loc_nrg_NumberOfDefinedBenefitPlans_17bbd09f-2990-45d2-86da-c7859ee5fd04" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanExpectedFutureEmployerContributionsNextFiscalYear_28e340c5-93d3-42cc-b46e-83e2e388e7fb" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanExpectedFutureEmployerContributionsNextFiscalYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_0c5a4cc1-5de2-4ddb-90ef-ee80ff7948d1" xlink:to="loc_us-gaap_DefinedBenefitPlanExpectedFutureEmployerContributionsNextFiscalYear_28e340c5-93d3-42cc-b46e-83e2e388e7fb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanActuarialGainLoss_20b810a4-9c10-42a0-8cac-9b015c8ef086" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanActuarialGainLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_0c5a4cc1-5de2-4ddb-90ef-ee80ff7948d1" xlink:to="loc_us-gaap_DefinedBenefitPlanActuarialGainLoss_20b810a4-9c10-42a0-8cac-9b015c8ef086" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_9979ee54-5f20-46e5-a2f8-7bf45e795067" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_0c5a4cc1-5de2-4ddb-90ef-ee80ff7948d1" xlink:to="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_9979ee54-5f20-46e5-a2f8-7bf45e795067" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_3884fac2-de50-46b2-b220-f4b9c06cb3c0" xlink:href="https://xbrl.sec.gov/dei/2020/dei-2020-01-31.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_9979ee54-5f20-46e5-a2f8-7bf45e795067" xlink:to="loc_dei_LegalEntityAxis_3884fac2-de50-46b2-b220-f4b9c06cb3c0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_3884fac2-de50-46b2-b220-f4b9c06cb3c0_default" xlink:href="https://xbrl.sec.gov/dei/2020/dei-2020-01-31.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_3884fac2-de50-46b2-b220-f4b9c06cb3c0" xlink:to="loc_dei_EntityDomain_3884fac2-de50-46b2-b220-f4b9c06cb3c0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_91629bfe-8982-44de-aeda-18b247129a5c" xlink:href="https://xbrl.sec.gov/dei/2020/dei-2020-01-31.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_3884fac2-de50-46b2-b220-f4b9c06cb3c0" xlink:to="loc_dei_EntityDomain_91629bfe-8982-44de-aeda-18b247129a5c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_GenOnMember_743af0f0-8101-4733-a1aa-40c8d0a93ae1" xlink:href="nrg-20201231.xsd#nrg_GenOnMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_91629bfe-8982-44de-aeda-18b247129a5c" xlink:to="loc_nrg_GenOnMember_743af0f0-8101-4733-a1aa-40c8d0a93ae1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringPlanAxis_b681f2dd-e3e4-4a1e-b66c-9d37939ac4d9" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RestructuringPlanAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_9979ee54-5f20-46e5-a2f8-7bf45e795067" xlink:to="loc_us-gaap_RestructuringPlanAxis_b681f2dd-e3e4-4a1e-b66c-9d37939ac4d9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringPlanDomain_b681f2dd-e3e4-4a1e-b66c-9d37939ac4d9_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RestructuringPlanDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RestructuringPlanAxis_b681f2dd-e3e4-4a1e-b66c-9d37939ac4d9" xlink:to="loc_us-gaap_RestructuringPlanDomain_b681f2dd-e3e4-4a1e-b66c-9d37939ac4d9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringPlanDomain_6ea53a20-2d27-48fe-bb1a-15f6855c2411" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RestructuringPlanDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RestructuringPlanAxis_b681f2dd-e3e4-4a1e-b66c-9d37939ac4d9" xlink:to="loc_us-gaap_RestructuringPlanDomain_6ea53a20-2d27-48fe-bb1a-15f6855c2411" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_RestructuringSupportAgreementMember_9afdb8a9-a0b5-410e-b4ea-83ffa86f9f2f" xlink:href="nrg-20201231.xsd#nrg_RestructuringSupportAgreementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringPlanDomain_6ea53a20-2d27-48fe-bb1a-15f6855c2411" xlink:to="loc_nrg_RestructuringSupportAgreementMember_9afdb8a9-a0b5-410e-b4ea-83ffa86f9f2f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTypeAxis_60f70743-264a-4c7c-b368-7275cbfac958" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RetirementPlanTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_9979ee54-5f20-46e5-a2f8-7bf45e795067" xlink:to="loc_us-gaap_RetirementPlanTypeAxis_60f70743-264a-4c7c-b368-7275cbfac958" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTypeDomain_60f70743-264a-4c7c-b368-7275cbfac958_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RetirementPlanTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RetirementPlanTypeAxis_60f70743-264a-4c7c-b368-7275cbfac958" xlink:to="loc_us-gaap_RetirementPlanTypeDomain_60f70743-264a-4c7c-b368-7275cbfac958_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTypeDomain_84252e14-c089-4a59-9b5c-8be0f8ebf4db" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RetirementPlanTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RetirementPlanTypeAxis_60f70743-264a-4c7c-b368-7275cbfac958" xlink:to="loc_us-gaap_RetirementPlanTypeDomain_84252e14-c089-4a59-9b5c-8be0f8ebf4db" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PensionPlansDefinedBenefitMember_84b6218b-8544-4978-918f-44c0f1037c32" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PensionPlansDefinedBenefitMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RetirementPlanTypeDomain_84252e14-c089-4a59-9b5c-8be0f8ebf4db" xlink:to="loc_us-gaap_PensionPlansDefinedBenefitMember_84b6218b-8544-4978-918f-44c0f1037c32" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/BenefitPlansandOtherPostretirementBenefitsNetBenefitCostsandFundedStatusDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#BenefitPlansandOtherPostretirementBenefitsNetBenefitCostsandFundedStatusDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/BenefitPlansandOtherPostretirementBenefitsNetBenefitCostsandFundedStatusDetails" xlink:type="extended" id="ib37dc3016db649f9aad9a4e3b0f17b38_BenefitPlansandOtherPostretirementBenefitsNetBenefitCostsandFundedStatusDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_efd482c9-2a2c-4ad8-a62a-2db8fb3c4598" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanDisclosureLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanNetPeriodicBenefitCostAbstract_418bf1e2-cefc-43e7-ad7c-8a913bfad02b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanNetPeriodicBenefitCostAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_efd482c9-2a2c-4ad8-a62a-2db8fb3c4598" xlink:to="loc_us-gaap_DefinedBenefitPlanNetPeriodicBenefitCostAbstract_418bf1e2-cefc-43e7-ad7c-8a913bfad02b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanServiceCost_961ce594-8a4f-4816-b0fe-c0e888ab66bd" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanServiceCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanNetPeriodicBenefitCostAbstract_418bf1e2-cefc-43e7-ad7c-8a913bfad02b" xlink:to="loc_us-gaap_DefinedBenefitPlanServiceCost_961ce594-8a4f-4816-b0fe-c0e888ab66bd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanInterestCost_2f4b7137-4544-4a26-ad49-1688d6ebfbb4" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanInterestCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanNetPeriodicBenefitCostAbstract_418bf1e2-cefc-43e7-ad7c-8a913bfad02b" xlink:to="loc_us-gaap_DefinedBenefitPlanInterestCost_2f4b7137-4544-4a26-ad49-1688d6ebfbb4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanExpectedReturnOnPlanAssets_31bcf49c-3eff-469b-bc3d-37b2537b936b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanExpectedReturnOnPlanAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanNetPeriodicBenefitCostAbstract_418bf1e2-cefc-43e7-ad7c-8a913bfad02b" xlink:to="loc_us-gaap_DefinedBenefitPlanExpectedReturnOnPlanAssets_31bcf49c-3eff-469b-bc3d-37b2537b936b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanAmortizationOfPriorServiceCostCredit_16c4280e-d1a1-49cd-8031-c62da0d5b067" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanAmortizationOfPriorServiceCostCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanNetPeriodicBenefitCostAbstract_418bf1e2-cefc-43e7-ad7c-8a913bfad02b" xlink:to="loc_us-gaap_DefinedBenefitPlanAmortizationOfPriorServiceCostCredit_16c4280e-d1a1-49cd-8031-c62da0d5b067" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanAmortizationOfGainsLosses_3a770c0c-0eb2-4a96-b115-09d0c286dc34" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanAmortizationOfGainsLosses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanNetPeriodicBenefitCostAbstract_418bf1e2-cefc-43e7-ad7c-8a913bfad02b" xlink:to="loc_us-gaap_DefinedBenefitPlanAmortizationOfGainsLosses_3a770c0c-0eb2-4a96-b115-09d0c286dc34" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanRecognizedNetGainLossDueToCurtailments_02150b8c-4ea9-44dd-89cf-2019f4e0f41d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanRecognizedNetGainLossDueToCurtailments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanNetPeriodicBenefitCostAbstract_418bf1e2-cefc-43e7-ad7c-8a913bfad02b" xlink:to="loc_us-gaap_DefinedBenefitPlanRecognizedNetGainLossDueToCurtailments_02150b8c-4ea9-44dd-89cf-2019f4e0f41d" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost_9a28bb95-8bfc-4b06-bb4d-c13bc4286a45" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanNetPeriodicBenefitCostAbstract_418bf1e2-cefc-43e7-ad7c-8a913bfad02b" xlink:to="loc_us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost_9a28bb95-8bfc-4b06-bb4d-c13bc4286a45" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanChangeInBenefitObligationRollForward_e23c32bb-1185-4b64-9f2e-6ec44ce71e8c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanChangeInBenefitObligationRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_efd482c9-2a2c-4ad8-a62a-2db8fb3c4598" xlink:to="loc_us-gaap_DefinedBenefitPlanChangeInBenefitObligationRollForward_e23c32bb-1185-4b64-9f2e-6ec44ce71e8c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanBenefitObligation_35202da0-5823-4561-96e5-348ae5f38d94" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanBenefitObligation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanChangeInBenefitObligationRollForward_e23c32bb-1185-4b64-9f2e-6ec44ce71e8c" xlink:to="loc_us-gaap_DefinedBenefitPlanBenefitObligation_35202da0-5823-4561-96e5-348ae5f38d94" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanServiceCost_3d432132-6fc0-45b3-a5ac-6b22d3aa5cee" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanServiceCost"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanInterestCost_5d7a82f6-6d12-42e7-9455-44f6ef391c21" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanInterestCost"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanPlanAmendments_e3012ea5-9852-4f18-8dea-564986ba2975" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanPlanAmendments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanChangeInBenefitObligationRollForward_e23c32bb-1185-4b64-9f2e-6ec44ce71e8c" xlink:to="loc_us-gaap_DefinedBenefitPlanPlanAmendments_e3012ea5-9852-4f18-8dea-564986ba2975" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanActuarialGainLoss_7d2eefd2-f4b1-47d7-a9de-41ee51e1d6bd" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanActuarialGainLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanChangeInBenefitObligationRollForward_e23c32bb-1185-4b64-9f2e-6ec44ce71e8c" xlink:to="loc_us-gaap_DefinedBenefitPlanActuarialGainLoss_7d2eefd2-f4b1-47d7-a9de-41ee51e1d6bd" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanBenefitObligationContributionsByPlanParticipant_2af80212-835e-4f68-bcbd-03fde32a1c8f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanBenefitObligationContributionsByPlanParticipant"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanChangeInBenefitObligationRollForward_e23c32bb-1185-4b64-9f2e-6ec44ce71e8c" xlink:to="loc_us-gaap_DefinedBenefitPlanBenefitObligationContributionsByPlanParticipant_2af80212-835e-4f68-bcbd-03fde32a1c8f" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanBenefitObligationBenefitsPaid_7a7d1636-e443-4430-9604-d808f69febcd" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanBenefitObligationBenefitsPaid"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanChangeInBenefitObligationRollForward_e23c32bb-1185-4b64-9f2e-6ec44ce71e8c" xlink:to="loc_us-gaap_DefinedBenefitPlanBenefitObligationBenefitsPaid_7a7d1636-e443-4430-9604-d808f69febcd" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanBenefitObligation_dcdcdc71-2975-4690-ac4c-1ae80a28b6cb" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanBenefitObligation"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanChangeInFairValueOfPlanAssetsRollForward_efe8afb2-942d-4a4b-a017-67603f8c583f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanChangeInFairValueOfPlanAssetsRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_efd482c9-2a2c-4ad8-a62a-2db8fb3c4598" xlink:to="loc_us-gaap_DefinedBenefitPlanChangeInFairValueOfPlanAssetsRollForward_efe8afb2-942d-4a4b-a017-67603f8c583f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanFairValueOfPlanAssets_846d34bd-09e4-4aea-9c89-ba15102cc71e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanFairValueOfPlanAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanChangeInFairValueOfPlanAssetsRollForward_efe8afb2-942d-4a4b-a017-67603f8c583f" xlink:to="loc_us-gaap_DefinedBenefitPlanFairValueOfPlanAssets_846d34bd-09e4-4aea-9c89-ba15102cc71e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanActualReturnOnPlanAssets_d2ebab36-5bdd-470b-897a-0f7456eca382" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanActualReturnOnPlanAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanChangeInFairValueOfPlanAssetsRollForward_efe8afb2-942d-4a4b-a017-67603f8c583f" xlink:to="loc_us-gaap_DefinedBenefitPlanActualReturnOnPlanAssets_d2ebab36-5bdd-470b-897a-0f7456eca382" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanPlanAssetsContributionsByPlanParticipant_ed67decc-af77-4fe5-be13-f694d9db173f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanPlanAssetsContributionsByPlanParticipant"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanChangeInFairValueOfPlanAssetsRollForward_efe8afb2-942d-4a4b-a017-67603f8c583f" xlink:to="loc_us-gaap_DefinedBenefitPlanPlanAssetsContributionsByPlanParticipant_ed67decc-af77-4fe5-be13-f694d9db173f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanContributionsByEmployer_e525acec-5e6b-4730-9285-29bb58c3f86a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanContributionsByEmployer"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanChangeInFairValueOfPlanAssetsRollForward_efe8afb2-942d-4a4b-a017-67603f8c583f" xlink:to="loc_us-gaap_DefinedBenefitPlanContributionsByEmployer_e525acec-5e6b-4730-9285-29bb58c3f86a" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanPlanAssetsBenefitsPaid_88401851-706d-4e4e-9ebb-710c10244eb0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanPlanAssetsBenefitsPaid"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanChangeInFairValueOfPlanAssetsRollForward_efe8afb2-942d-4a4b-a017-67603f8c583f" xlink:to="loc_us-gaap_DefinedBenefitPlanPlanAssetsBenefitsPaid_88401851-706d-4e4e-9ebb-710c10244eb0" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanFairValueOfPlanAssets_6a912a3f-6824-4d5c-868c-573a08a6466a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanFairValueOfPlanAssets"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanFundedStatusOfPlan_da01ed6d-2ab0-4b8d-9a91-e0952061c601" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanFundedStatusOfPlan"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_efd482c9-2a2c-4ad8-a62a-2db8fb3c4598" xlink:to="loc_us-gaap_DefinedBenefitPlanFundedStatusOfPlan_da01ed6d-2ab0-4b8d-9a91-e0952061c601" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_c9f259f4-19eb-4682-b5a9-f0fa0951070e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_efd482c9-2a2c-4ad8-a62a-2db8fb3c4598" xlink:to="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_c9f259f4-19eb-4682-b5a9-f0fa0951070e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTypeAxis_b2c43908-35b1-449b-bbc9-3844f3a4e74f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RetirementPlanTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_c9f259f4-19eb-4682-b5a9-f0fa0951070e" xlink:to="loc_us-gaap_RetirementPlanTypeAxis_b2c43908-35b1-449b-bbc9-3844f3a4e74f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTypeDomain_b2c43908-35b1-449b-bbc9-3844f3a4e74f_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RetirementPlanTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RetirementPlanTypeAxis_b2c43908-35b1-449b-bbc9-3844f3a4e74f" xlink:to="loc_us-gaap_RetirementPlanTypeDomain_b2c43908-35b1-449b-bbc9-3844f3a4e74f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTypeDomain_288b05cb-c1d5-444d-9d0f-25fd0f07ceb4" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RetirementPlanTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RetirementPlanTypeAxis_b2c43908-35b1-449b-bbc9-3844f3a4e74f" xlink:to="loc_us-gaap_RetirementPlanTypeDomain_288b05cb-c1d5-444d-9d0f-25fd0f07ceb4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PensionPlansDefinedBenefitMember_7e0c7a07-6714-4648-a21c-50aa18b3706a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PensionPlansDefinedBenefitMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RetirementPlanTypeDomain_288b05cb-c1d5-444d-9d0f-25fd0f07ceb4" xlink:to="loc_us-gaap_PensionPlansDefinedBenefitMember_7e0c7a07-6714-4648-a21c-50aa18b3706a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember_1a49aaaa-e723-4e1c-8891-e749ddae5a6e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RetirementPlanTypeDomain_288b05cb-c1d5-444d-9d0f-25fd0f07ceb4" xlink:to="loc_us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember_1a49aaaa-e723-4e1c-8891-e749ddae5a6e" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/BenefitPlansandOtherPostretirementBenefitsAmountsRecognizedintheBalanceSheetsandOCIDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#BenefitPlansandOtherPostretirementBenefitsAmountsRecognizedintheBalanceSheetsandOCIDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/BenefitPlansandOtherPostretirementBenefitsAmountsRecognizedintheBalanceSheetsandOCIDetails" xlink:type="extended" id="i710c235e405645ea9fd60dc0c447d24d_BenefitPlansandOtherPostretirementBenefitsAmountsRecognizedintheBalanceSheetsandOCIDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_c5039004-dcb9-45e3-aa40-305ff087510f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanDisclosureLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanAmountsRecognizedInBalanceSheetAbstract_0a781571-36e9-4ec3-ba15-f94630948357" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanAmountsRecognizedInBalanceSheetAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_c5039004-dcb9-45e3-aa40-305ff087510f" xlink:to="loc_us-gaap_DefinedBenefitPlanAmountsRecognizedInBalanceSheetAbstract_0a781571-36e9-4ec3-ba15-f94630948357" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PensionAndOtherPostretirementDefinedBenefitPlansCurrentLiabilities_31253ef6-76a3-4bfd-8697-a48151882eab" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PensionAndOtherPostretirementDefinedBenefitPlansCurrentLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanAmountsRecognizedInBalanceSheetAbstract_0a781571-36e9-4ec3-ba15-f94630948357" xlink:to="loc_us-gaap_PensionAndOtherPostretirementDefinedBenefitPlansCurrentLiabilities_31253ef6-76a3-4bfd-8697-a48151882eab" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent_be13e2fd-ddea-4dda-ba5b-1ded57a03aca" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanAmountsRecognizedInBalanceSheetAbstract_0a781571-36e9-4ec3-ba15-f94630948357" xlink:to="loc_us-gaap_PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent_be13e2fd-ddea-4dda-ba5b-1ded57a03aca" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeBeforeTaxAbstract_50f09601-cf69-4a97-9451-02d1820b369a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeBeforeTaxAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_c5039004-dcb9-45e3-aa40-305ff087510f" xlink:to="loc_us-gaap_DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeBeforeTaxAbstract_50f09601-cf69-4a97-9451-02d1820b369a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeNetGainsLossesBeforeTax_054916af-cdd4-45ad-b3f8-e492074cf385" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeNetGainsLossesBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeBeforeTaxAbstract_50f09601-cf69-4a97-9451-02d1820b369a" xlink:to="loc_us-gaap_DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeNetGainsLossesBeforeTax_054916af-cdd4-45ad-b3f8-e492074cf385" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeNetPriorServiceCostCreditBeforeTax_80281204-ba4b-470d-bac8-85cb8e263505" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeNetPriorServiceCostCreditBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeBeforeTaxAbstract_50f09601-cf69-4a97-9451-02d1820b369a" xlink:to="loc_us-gaap_DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeNetPriorServiceCostCreditBeforeTax_80281204-ba4b-470d-bac8-85cb8e263505" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeBeforeTax_8bc2fe13-ca9b-4396-8f2b-6e9ebe810def" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeBeforeTaxAbstract_50f09601-cf69-4a97-9451-02d1820b369a" xlink:to="loc_us-gaap_DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeBeforeTax_8bc2fe13-ca9b-4396-8f2b-6e9ebe810def" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentBeforeTaxPeriodIncreaseDecreaseAbstract_2a3874e4-32de-474a-82ad-b72b2487d208" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentBeforeTaxPeriodIncreaseDecreaseAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_c5039004-dcb9-45e3-aa40-305ff087510f" xlink:to="loc_us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentBeforeTaxPeriodIncreaseDecreaseAbstract_2a3874e4-32de-474a-82ad-b72b2487d208" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansNetUnamortizedGainLossArisingDuringPeriodBeforeTax_18259da0-0579-4ad8-b650-d461f895f342" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansNetUnamortizedGainLossArisingDuringPeriodBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentBeforeTaxPeriodIncreaseDecreaseAbstract_2a3874e4-32de-474a-82ad-b72b2487d208" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansNetUnamortizedGainLossArisingDuringPeriodBeforeTax_18259da0-0579-4ad8-b650-d461f895f342" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanAmortizationOfGainsLosses_cbf91c4d-37dc-4b33-a7a5-e3ead3266f8e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanAmortizationOfGainsLosses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentBeforeTaxPeriodIncreaseDecreaseAbstract_2a3874e4-32de-474a-82ad-b72b2487d208" xlink:to="loc_us-gaap_DefinedBenefitPlanAmortizationOfGainsLosses_cbf91c4d-37dc-4b33-a7a5-e3ead3266f8e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanAmountsRecognizedInOtherComprehensiveIncomeNetPriorServiceCostCreditBeforeTax_b39973f2-3ffa-4e96-8bac-3bdd51c5c921" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanAmountsRecognizedInOtherComprehensiveIncomeNetPriorServiceCostCreditBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentBeforeTaxPeriodIncreaseDecreaseAbstract_2a3874e4-32de-474a-82ad-b72b2487d208" xlink:to="loc_us-gaap_DefinedBenefitPlanAmountsRecognizedInOtherComprehensiveIncomeNetPriorServiceCostCreditBeforeTax_b39973f2-3ffa-4e96-8bac-3bdd51c5c921" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditBeforeTax_9d4c8724-fe2e-4497-81a0-1cf60c722282" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentBeforeTaxPeriodIncreaseDecreaseAbstract_2a3874e4-32de-474a-82ad-b72b2487d208" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditBeforeTax_9d4c8724-fe2e-4497-81a0-1cf60c722282" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeTax_73d6d46b-879b-41ec-9c1e-d73664d113c3" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentBeforeTaxPeriodIncreaseDecreaseAbstract_2a3874e4-32de-474a-82ad-b72b2487d208" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeTax_73d6d46b-879b-41ec-9c1e-d73664d113c3" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost_6d66abcb-605f-4de4-90e0-69c3eeb9c1f2" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentBeforeTaxPeriodIncreaseDecreaseAbstract_2a3874e4-32de-474a-82ad-b72b2487d208" xlink:to="loc_us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost_6d66abcb-605f-4de4-90e0-69c3eeb9c1f2" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmountRecognizedInNetPeriodicBenefitCostAndOtherComprehensiveIncomeLossBeforeTax_9ef03ae5-f974-45d1-a24c-a1cbfb4f24d1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AmountRecognizedInNetPeriodicBenefitCostAndOtherComprehensiveIncomeLossBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentBeforeTaxPeriodIncreaseDecreaseAbstract_2a3874e4-32de-474a-82ad-b72b2487d208" xlink:to="loc_us-gaap_AmountRecognizedInNetPeriodicBenefitCostAndOtherComprehensiveIncomeLossBeforeTax_9ef03ae5-f974-45d1-a24c-a1cbfb4f24d1" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_SignificantComponentsOfDefinedBenefitPensionPlanAbstract_8a7d7c2b-bc68-454f-8ba9-c8ec39f3e26f" xlink:href="nrg-20201231.xsd#nrg_SignificantComponentsOfDefinedBenefitPensionPlanAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_c5039004-dcb9-45e3-aa40-305ff087510f" xlink:to="loc_nrg_SignificantComponentsOfDefinedBenefitPensionPlanAbstract_8a7d7c2b-bc68-454f-8ba9-c8ec39f3e26f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanBenefitObligation_0ed248ca-5e8c-48c3-86da-03957a1c4d94" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanBenefitObligation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_SignificantComponentsOfDefinedBenefitPensionPlanAbstract_8a7d7c2b-bc68-454f-8ba9-c8ec39f3e26f" xlink:to="loc_us-gaap_DefinedBenefitPlanBenefitObligation_0ed248ca-5e8c-48c3-86da-03957a1c4d94" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanAccumulatedBenefitObligation_47b36903-a56a-4de3-b008-56f249379c69" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanAccumulatedBenefitObligation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_SignificantComponentsOfDefinedBenefitPensionPlanAbstract_8a7d7c2b-bc68-454f-8ba9-c8ec39f3e26f" xlink:to="loc_us-gaap_DefinedBenefitPlanAccumulatedBenefitObligation_47b36903-a56a-4de3-b008-56f249379c69" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanFairValueOfPlanAssets_123368d4-dc2c-45b2-b149-775091be42d3" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanFairValueOfPlanAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_SignificantComponentsOfDefinedBenefitPensionPlanAbstract_8a7d7c2b-bc68-454f-8ba9-c8ec39f3e26f" xlink:to="loc_us-gaap_DefinedBenefitPlanFairValueOfPlanAssets_123368d4-dc2c-45b2-b149-775091be42d3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_c606355a-9fbf-41a2-b442-6bc60ce6338c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_c5039004-dcb9-45e3-aa40-305ff087510f" xlink:to="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_c606355a-9fbf-41a2-b442-6bc60ce6338c" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTypeAxis_14a33c64-5182-4176-b78c-9113dd50ea1b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RetirementPlanTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_c606355a-9fbf-41a2-b442-6bc60ce6338c" xlink:to="loc_us-gaap_RetirementPlanTypeAxis_14a33c64-5182-4176-b78c-9113dd50ea1b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTypeDomain_14a33c64-5182-4176-b78c-9113dd50ea1b_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RetirementPlanTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RetirementPlanTypeAxis_14a33c64-5182-4176-b78c-9113dd50ea1b" xlink:to="loc_us-gaap_RetirementPlanTypeDomain_14a33c64-5182-4176-b78c-9113dd50ea1b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTypeDomain_e6ea5517-1ac1-4323-9be0-2aa80a786bad" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RetirementPlanTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RetirementPlanTypeAxis_14a33c64-5182-4176-b78c-9113dd50ea1b" xlink:to="loc_us-gaap_RetirementPlanTypeDomain_e6ea5517-1ac1-4323-9be0-2aa80a786bad" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PensionPlansDefinedBenefitMember_46f7566c-2e14-491d-8825-eede2e844191" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PensionPlansDefinedBenefitMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RetirementPlanTypeDomain_e6ea5517-1ac1-4323-9be0-2aa80a786bad" xlink:to="loc_us-gaap_PensionPlansDefinedBenefitMember_46f7566c-2e14-491d-8825-eede2e844191" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember_08615b24-6298-4686-957f-f995667ff6df" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RetirementPlanTypeDomain_e6ea5517-1ac1-4323-9be0-2aa80a786bad" xlink:to="loc_us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember_08615b24-6298-4686-957f-f995667ff6df" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/BenefitPlansandOtherPostretirementBenefitsFairValuesofPensionAssetsByAssetCategoryandLevelWithintheFairValueHierarchyDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#BenefitPlansandOtherPostretirementBenefitsFairValuesofPensionAssetsByAssetCategoryandLevelWithintheFairValueHierarchyDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/BenefitPlansandOtherPostretirementBenefitsFairValuesofPensionAssetsByAssetCategoryandLevelWithintheFairValueHierarchyDetails" xlink:type="extended" id="i703bbb82d15a4c7da8462a067ec7c2dc_BenefitPlansandOtherPostretirementBenefitsFairValuesofPensionAssetsByAssetCategoryandLevelWithintheFairValueHierarchyDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_8b753fa6-311a-4644-bcbe-55fb3bb67a2a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanDisclosureLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanFairValueOfPlanAssets_26675072-efd6-43d8-b2b6-b78b6b4730f5" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanFairValueOfPlanAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_8b753fa6-311a-4644-bcbe-55fb3bb67a2a" xlink:to="loc_us-gaap_DefinedBenefitPlanFairValueOfPlanAssets_26675072-efd6-43d8-b2b6-b78b6b4730f5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanWeightedAverageAssumptionsUsedInCalculatingBenefitObligationAbstract_ed4f9892-ecbf-4d15-b0aa-8c9963b20b9d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanWeightedAverageAssumptionsUsedInCalculatingBenefitObligationAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_8b753fa6-311a-4644-bcbe-55fb3bb67a2a" xlink:to="loc_us-gaap_DefinedBenefitPlanWeightedAverageAssumptionsUsedInCalculatingBenefitObligationAbstract_ed4f9892-ecbf-4d15-b0aa-8c9963b20b9d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate_a3e19c86-8bdb-41d1-bfaf-bde6d59ae831" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanWeightedAverageAssumptionsUsedInCalculatingBenefitObligationAbstract_ed4f9892-ecbf-4d15-b0aa-8c9963b20b9d" xlink:to="loc_us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate_a3e19c86-8bdb-41d1-bfaf-bde6d59ae831" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationWeightedAverageInterestCreditingRate_63088196-5359-4610-9c18-fd88f9a47092" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationWeightedAverageInterestCreditingRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanWeightedAverageAssumptionsUsedInCalculatingBenefitObligationAbstract_ed4f9892-ecbf-4d15-b0aa-8c9963b20b9d" xlink:to="loc_us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationWeightedAverageInterestCreditingRate_63088196-5359-4610-9c18-fd88f9a47092" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationRateOfCompensationIncrease_8dd7c259-aff6-45c7-841b-91412e25b522" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationRateOfCompensationIncrease"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanWeightedAverageAssumptionsUsedInCalculatingBenefitObligationAbstract_ed4f9892-ecbf-4d15-b0aa-8c9963b20b9d" xlink:to="loc_us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationRateOfCompensationIncrease_8dd7c259-aff6-45c7-841b-91412e25b522" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanHealthCareCostTrendRateAssumedNextFiscalYear_dc24a924-ddf6-4503-a78c-bff51399374b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanHealthCareCostTrendRateAssumedNextFiscalYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_8b753fa6-311a-4644-bcbe-55fb3bb67a2a" xlink:to="loc_us-gaap_DefinedBenefitPlanHealthCareCostTrendRateAssumedNextFiscalYear_dc24a924-ddf6-4503-a78c-bff51399374b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanYearHealthCareCostTrendRateReachesUltimateTrendRate_3ab74fd9-2017-41fa-bf04-938ec3127577" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanYearHealthCareCostTrendRateReachesUltimateTrendRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_8b753fa6-311a-4644-bcbe-55fb3bb67a2a" xlink:to="loc_us-gaap_DefinedBenefitPlanYearHealthCareCostTrendRateReachesUltimateTrendRate_3ab74fd9-2017-41fa-bf04-938ec3127577" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanWeightedAverageAssumptionsUsedInCalculatingNetPeriodicBenefitCostAbstract_7e997192-9435-4b59-989d-73f321db22a2" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanWeightedAverageAssumptionsUsedInCalculatingNetPeriodicBenefitCostAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_8b753fa6-311a-4644-bcbe-55fb3bb67a2a" xlink:to="loc_us-gaap_DefinedBenefitPlanWeightedAverageAssumptionsUsedInCalculatingNetPeriodicBenefitCostAbstract_7e997192-9435-4b59-989d-73f321db22a2" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostDiscountRate_f59fc408-c4fb-4699-ac4b-e819bbe949d5" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostDiscountRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanWeightedAverageAssumptionsUsedInCalculatingNetPeriodicBenefitCostAbstract_7e997192-9435-4b59-989d-73f321db22a2" xlink:to="loc_us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostDiscountRate_f59fc408-c4fb-4699-ac4b-e819bbe949d5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostWeightedAverageInterestCreditingRate_dcb935a9-3309-4846-96b1-11f13a0d9313" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostWeightedAverageInterestCreditingRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanWeightedAverageAssumptionsUsedInCalculatingNetPeriodicBenefitCostAbstract_7e997192-9435-4b59-989d-73f321db22a2" xlink:to="loc_us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostWeightedAverageInterestCreditingRate_dcb935a9-3309-4846-96b1-11f13a0d9313" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostExpectedLongTermReturnOnAssets_d3d0c9a8-e339-4c91-89b1-3ed9a70d633b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostExpectedLongTermReturnOnAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanWeightedAverageAssumptionsUsedInCalculatingNetPeriodicBenefitCostAbstract_7e997192-9435-4b59-989d-73f321db22a2" xlink:to="loc_us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostExpectedLongTermReturnOnAssets_d3d0c9a8-e339-4c91-89b1-3ed9a70d633b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostRateOfCompensationIncrease_e540aa76-8487-4934-8a56-dfb4946a3e9d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostRateOfCompensationIncrease"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanWeightedAverageAssumptionsUsedInCalculatingNetPeriodicBenefitCostAbstract_7e997192-9435-4b59-989d-73f321db22a2" xlink:to="loc_us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostRateOfCompensationIncrease_e540aa76-8487-4934-8a56-dfb4946a3e9d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_AonHewittAboveMedianYieldCurveDiscountRateYears_df420cf9-d3a8-4880-89a9-d9a5802d6ce6" xlink:href="nrg-20201231.xsd#nrg_AonHewittAboveMedianYieldCurveDiscountRateYears"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_8b753fa6-311a-4644-bcbe-55fb3bb67a2a" xlink:to="loc_nrg_AonHewittAboveMedianYieldCurveDiscountRateYears_df420cf9-d3a8-4880-89a9-d9a5802d6ce6" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanAssetsTargetAllocationsAbstract_8027397e-4281-4b15-93c7-e65a7feeb71c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanAssetsTargetAllocationsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_8b753fa6-311a-4644-bcbe-55fb3bb67a2a" xlink:to="loc_us-gaap_DefinedBenefitPlanAssetsTargetAllocationsAbstract_8027397e-4281-4b15-93c7-e65a7feeb71c" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanPlanAssetsTargetAllocationPercentage_0cb5d60a-0309-41f7-b0cf-257adf6770d4" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanPlanAssetsTargetAllocationPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanAssetsTargetAllocationsAbstract_8027397e-4281-4b15-93c7-e65a7feeb71c" xlink:to="loc_us-gaap_DefinedBenefitPlanPlanAssetsTargetAllocationPercentage_0cb5d60a-0309-41f7-b0cf-257adf6770d4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_72666937-b3c1-416d-b103-bc529e3f28db" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_8b753fa6-311a-4644-bcbe-55fb3bb67a2a" xlink:to="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_72666937-b3c1-416d-b103-bc529e3f28db" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTypeAxis_cbfbf2bf-4ef7-4587-a33d-aed00aa562f8" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RetirementPlanTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_72666937-b3c1-416d-b103-bc529e3f28db" xlink:to="loc_us-gaap_RetirementPlanTypeAxis_cbfbf2bf-4ef7-4587-a33d-aed00aa562f8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTypeDomain_cbfbf2bf-4ef7-4587-a33d-aed00aa562f8_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RetirementPlanTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RetirementPlanTypeAxis_cbfbf2bf-4ef7-4587-a33d-aed00aa562f8" xlink:to="loc_us-gaap_RetirementPlanTypeDomain_cbfbf2bf-4ef7-4587-a33d-aed00aa562f8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTypeDomain_c8d7215f-7d69-48dc-8d3e-166faa1393a1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RetirementPlanTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RetirementPlanTypeAxis_cbfbf2bf-4ef7-4587-a33d-aed00aa562f8" xlink:to="loc_us-gaap_RetirementPlanTypeDomain_c8d7215f-7d69-48dc-8d3e-166faa1393a1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PensionPlansDefinedBenefitMember_ed33a153-0fd1-41ec-8d01-51bdb346b37a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PensionPlansDefinedBenefitMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RetirementPlanTypeDomain_c8d7215f-7d69-48dc-8d3e-166faa1393a1" xlink:to="loc_us-gaap_PensionPlansDefinedBenefitMember_ed33a153-0fd1-41ec-8d01-51bdb346b37a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember_bff31f5c-7f0a-4430-97b1-beefae6f1827" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RetirementPlanTypeDomain_c8d7215f-7d69-48dc-8d3e-166faa1393a1" xlink:to="loc_us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember_bff31f5c-7f0a-4430-97b1-beefae6f1827" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_2117d1ca-c58a-4c8e-a5dc-f02b311340dc" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_72666937-b3c1-416d-b103-bc529e3f28db" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_2117d1ca-c58a-4c8e-a5dc-f02b311340dc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_2117d1ca-c58a-4c8e-a5dc-f02b311340dc_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_2117d1ca-c58a-4c8e-a5dc-f02b311340dc" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_2117d1ca-c58a-4c8e-a5dc-f02b311340dc_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_a34ad05d-9c80-4f42-8afa-4d200291c559" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_2117d1ca-c58a-4c8e-a5dc-f02b311340dc" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_a34ad05d-9c80-4f42-8afa-4d200291c559" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_3889e444-4fb4-45a7-8d16-9bf80c1f1ff7" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueInputsLevel1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_a34ad05d-9c80-4f42-8afa-4d200291c559" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_3889e444-4fb4-45a7-8d16-9bf80c1f1ff7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_6b87e550-6ec0-42f7-a519-b7abb147c354" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_a34ad05d-9c80-4f42-8afa-4d200291c559" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_6b87e550-6ec0-42f7-a519-b7abb147c354" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel12And3Member_582de675-6e5d-45cb-ae4b-6473965b1175" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueInputsLevel12And3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_a34ad05d-9c80-4f42-8afa-4d200291c559" xlink:to="loc_us-gaap_FairValueInputsLevel12And3Member_582de675-6e5d-45cb-ae4b-6473965b1175" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasuredAtNetAssetValuePerShareMember_09ee77ec-80f4-4e73-8fef-1c2e5cf7e41c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueMeasuredAtNetAssetValuePerShareMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_a34ad05d-9c80-4f42-8afa-4d200291c559" xlink:to="loc_us-gaap_FairValueMeasuredAtNetAssetValuePerShareMember_09ee77ec-80f4-4e73-8fef-1c2e5cf7e41c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis_c76cec2c-cbf7-4f7e-b1f4-395792242377" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_72666937-b3c1-416d-b103-bc529e3f28db" xlink:to="loc_us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis_c76cec2c-cbf7-4f7e-b1f4-395792242377" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanAssetCategoriesDomain_c76cec2c-cbf7-4f7e-b1f4-395792242377_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PlanAssetCategoriesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis_c76cec2c-cbf7-4f7e-b1f4-395792242377" xlink:to="loc_us-gaap_PlanAssetCategoriesDomain_c76cec2c-cbf7-4f7e-b1f4-395792242377_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanAssetCategoriesDomain_59660fb2-73e1-49cf-bde9-bdda6c0cab66" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PlanAssetCategoriesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis_c76cec2c-cbf7-4f7e-b1f4-395792242377" xlink:to="loc_us-gaap_PlanAssetCategoriesDomain_59660fb2-73e1-49cf-bde9-bdda6c0cab66" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_CommonTrustInvestmentUsEquitySecuritiesMember_b51075f8-40ab-4a64-9b7e-d0edf7eb2f92" xlink:href="nrg-20201231.xsd#nrg_CommonTrustInvestmentUsEquitySecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanAssetCategoriesDomain_59660fb2-73e1-49cf-bde9-bdda6c0cab66" xlink:to="loc_nrg_CommonTrustInvestmentUsEquitySecuritiesMember_b51075f8-40ab-4a64-9b7e-d0edf7eb2f92" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_CommonTrustInvestmentNonUsEquitySecuritiesMember_8f20ecad-3730-427b-b32e-d9ea3072b090" xlink:href="nrg-20201231.xsd#nrg_CommonTrustInvestmentNonUsEquitySecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanAssetCategoriesDomain_59660fb2-73e1-49cf-bde9-bdda6c0cab66" xlink:to="loc_nrg_CommonTrustInvestmentNonUsEquitySecuritiesMember_8f20ecad-3730-427b-b32e-d9ea3072b090" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_EmergingMarketEquitiesMember_ae4fbda4-ad43-42d3-b038-a5b59610fc7f" xlink:href="nrg-20201231.xsd#nrg_EmergingMarketEquitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanAssetCategoriesDomain_59660fb2-73e1-49cf-bde9-bdda6c0cab66" xlink:to="loc_nrg_EmergingMarketEquitiesMember_ae4fbda4-ad43-42d3-b038-a5b59610fc7f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_CommonTrustInvestmentFixedIncomeSecuritiesMember_79b23267-4131-4001-b2d9-965f32559c2d" xlink:href="nrg-20201231.xsd#nrg_CommonTrustInvestmentFixedIncomeSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanAssetCategoriesDomain_59660fb2-73e1-49cf-bde9-bdda6c0cab66" xlink:to="loc_nrg_CommonTrustInvestmentFixedIncomeSecuritiesMember_79b23267-4131-4001-b2d9-965f32559c2d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermInvestmentsMember_432029ce-9f1a-4d08-b986-c4c9b02939d6" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShortTermInvestmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanAssetCategoriesDomain_59660fb2-73e1-49cf-bde9-bdda6c0cab66" xlink:to="loc_us-gaap_ShortTermInvestmentsMember_432029ce-9f1a-4d08-b986-c4c9b02939d6" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnershipMember_d30d0d5c-7341-4fb5-aab0-7d560a450b7a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PartnershipMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanAssetCategoriesDomain_59660fb2-73e1-49cf-bde9-bdda6c0cab66" xlink:to="loc_us-gaap_PartnershipMember_d30d0d5c-7341-4fb5-aab0-7d560a450b7a" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_AccountTypeAxis_a4afdac2-a9c4-4424-a469-0300d1bb44c2" xlink:href="nrg-20201231.xsd#nrg_AccountTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_72666937-b3c1-416d-b103-bc529e3f28db" xlink:to="loc_nrg_AccountTypeAxis_a4afdac2-a9c4-4424-a469-0300d1bb44c2" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_AccountTypeDomain_a4afdac2-a9c4-4424-a469-0300d1bb44c2_default" xlink:href="nrg-20201231.xsd#nrg_AccountTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_nrg_AccountTypeAxis_a4afdac2-a9c4-4424-a469-0300d1bb44c2" xlink:to="loc_nrg_AccountTypeDomain_a4afdac2-a9c4-4424-a469-0300d1bb44c2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_AccountTypeDomain_c3fd6c52-8bce-48eb-a648-6d8dccb0bb6e" xlink:href="nrg-20201231.xsd#nrg_AccountTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_nrg_AccountTypeAxis_a4afdac2-a9c4-4424-a469-0300d1bb44c2" xlink:to="loc_nrg_AccountTypeDomain_c3fd6c52-8bce-48eb-a648-6d8dccb0bb6e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_PostretirementBenefitObligationMember_ebf6baa3-6d67-4dcc-b638-fae892cb3338" xlink:href="nrg-20201231.xsd#nrg_PostretirementBenefitObligationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_AccountTypeDomain_c3fd6c52-8bce-48eb-a648-6d8dccb0bb6e" xlink:to="loc_nrg_PostretirementBenefitObligationMember_ebf6baa3-6d67-4dcc-b638-fae892cb3338" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_NetPeriodBenefitCostCreditMember_153a0bad-1aec-47ab-8e25-14cff8dd3821" xlink:href="nrg-20201231.xsd#nrg_NetPeriodBenefitCostCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_AccountTypeDomain_c3fd6c52-8bce-48eb-a648-6d8dccb0bb6e" xlink:to="loc_nrg_NetPeriodBenefitCostCreditMember_153a0bad-1aec-47ab-8e25-14cff8dd3821" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_GroupofIndividualsAxis_0160e8e8-1c3a-40af-896f-eace2da725ad" xlink:href="nrg-20201231.xsd#nrg_GroupofIndividualsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_72666937-b3c1-416d-b103-bc529e3f28db" xlink:to="loc_nrg_GroupofIndividualsAxis_0160e8e8-1c3a-40af-896f-eace2da725ad" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_GroupofIndividualsDomain_0160e8e8-1c3a-40af-896f-eace2da725ad_default" xlink:href="nrg-20201231.xsd#nrg_GroupofIndividualsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_nrg_GroupofIndividualsAxis_0160e8e8-1c3a-40af-896f-eace2da725ad" xlink:to="loc_nrg_GroupofIndividualsDomain_0160e8e8-1c3a-40af-896f-eace2da725ad_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_GroupofIndividualsDomain_5eedf01d-5204-4dbf-83bb-79a91f98658c" xlink:href="nrg-20201231.xsd#nrg_GroupofIndividualsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_nrg_GroupofIndividualsAxis_0160e8e8-1c3a-40af-896f-eace2da725ad" xlink:to="loc_nrg_GroupofIndividualsDomain_5eedf01d-5204-4dbf-83bb-79a91f98658c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_Beforeage65Member_b4f18148-6139-46ed-b108-3ef312f43ed7" xlink:href="nrg-20201231.xsd#nrg_Beforeage65Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_GroupofIndividualsDomain_5eedf01d-5204-4dbf-83bb-79a91f98658c" xlink:to="loc_nrg_Beforeage65Member_b4f18148-6139-46ed-b108-3ef312f43ed7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_Age65andafterMember_118862ff-4e73-40ee-8be4-080dee9d9f04" xlink:href="nrg-20201231.xsd#nrg_Age65andafterMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_GroupofIndividualsDomain_5eedf01d-5204-4dbf-83bb-79a91f98658c" xlink:to="loc_nrg_Age65andafterMember_118862ff-4e73-40ee-8be4-080dee9d9f04" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_8ae269ba-645f-4460-9ee1-d41c13450833" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_72666937-b3c1-416d-b103-bc529e3f28db" xlink:to="loc_srt_RangeAxis_8ae269ba-645f-4460-9ee1-d41c13450833" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_8ae269ba-645f-4460-9ee1-d41c13450833_default" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_8ae269ba-645f-4460-9ee1-d41c13450833" xlink:to="loc_srt_RangeMember_8ae269ba-645f-4460-9ee1-d41c13450833_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_ae597712-0640-4e75-9bff-fb49fcb7e83b" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_8ae269ba-645f-4460-9ee1-d41c13450833" xlink:to="loc_srt_RangeMember_ae597712-0640-4e75-9bff-fb49fcb7e83b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_b5dd7c63-6cb2-4d0a-a5e3-2d7b3375465b" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_ae597712-0640-4e75-9bff-fb49fcb7e83b" xlink:to="loc_srt_MinimumMember_b5dd7c63-6cb2-4d0a-a5e3-2d7b3375465b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_1859971e-5443-4812-a30a-7a9183ae27d1" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_ae597712-0640-4e75-9bff-fb49fcb7e83b" xlink:to="loc_srt_MaximumMember_1859971e-5443-4812-a30a-7a9183ae27d1" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/BenefitPlansandOtherPostretirementBenefitsExpectedFutureBenefitPaymentsFortheNextFiveYearsandOtherDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#BenefitPlansandOtherPostretirementBenefitsExpectedFutureBenefitPaymentsFortheNextFiveYearsandOtherDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/BenefitPlansandOtherPostretirementBenefitsExpectedFutureBenefitPaymentsFortheNextFiveYearsandOtherDetails" xlink:type="extended" id="i7dcca3a6017042d7aa7de6b9dd2f9455_BenefitPlansandOtherPostretirementBenefitsExpectedFutureBenefitPaymentsFortheNextFiveYearsandOtherDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_68bc56a6-bf57-43f0-bf77-d1f435cb8940" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanDisclosureLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanEstimatedFutureBenefitPaymentsAbstract_0c4cdab0-2f53-4115-81a3-0b24ee26a3d9" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanEstimatedFutureBenefitPaymentsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_68bc56a6-bf57-43f0-bf77-d1f435cb8940" xlink:to="loc_us-gaap_DefinedBenefitPlanEstimatedFutureBenefitPaymentsAbstract_0c4cdab0-2f53-4115-81a3-0b24ee26a3d9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsNextTwelveMonths_ebbc5092-3586-4f97-8c2b-cdf9f11f2781" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsNextTwelveMonths"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanEstimatedFutureBenefitPaymentsAbstract_0c4cdab0-2f53-4115-81a3-0b24ee26a3d9" xlink:to="loc_us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsNextTwelveMonths_ebbc5092-3586-4f97-8c2b-cdf9f11f2781" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearTwo_14f19296-3a26-45ad-846e-1033a91fffaa" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearTwo"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanEstimatedFutureBenefitPaymentsAbstract_0c4cdab0-2f53-4115-81a3-0b24ee26a3d9" xlink:to="loc_us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearTwo_14f19296-3a26-45ad-846e-1033a91fffaa" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearThree_2fd62e63-2897-4acb-a5d3-dac7547c421b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearThree"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanEstimatedFutureBenefitPaymentsAbstract_0c4cdab0-2f53-4115-81a3-0b24ee26a3d9" xlink:to="loc_us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearThree_2fd62e63-2897-4acb-a5d3-dac7547c421b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFour_c04af900-1aad-4699-9222-6f123a282ef1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFour"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanEstimatedFutureBenefitPaymentsAbstract_0c4cdab0-2f53-4115-81a3-0b24ee26a3d9" xlink:to="loc_us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFour_c04af900-1aad-4699-9222-6f123a282ef1" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFive_ea61c836-31f1-4b66-94e3-13f2d3f91922" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFive"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanEstimatedFutureBenefitPaymentsAbstract_0c4cdab0-2f53-4115-81a3-0b24ee26a3d9" xlink:to="loc_us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFive_ea61c836-31f1-4b66-94e3-13f2d3f91922" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsFiveFiscalYearsThereafter_9e491f3f-2ee5-43c8-924d-81288845bd1f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsFiveFiscalYearsThereafter"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanEstimatedFutureBenefitPaymentsAbstract_0c4cdab0-2f53-4115-81a3-0b24ee26a3d9" xlink:to="loc_us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsFiveFiscalYearsThereafter_9e491f3f-2ee5-43c8-924d-81288845bd1f" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PostretirementMedicalPlansWithPrescriptionDrugBenefitsAbstract_18e46edd-302d-4a4c-b95b-f47c03ff3c90" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PostretirementMedicalPlansWithPrescriptionDrugBenefitsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_68bc56a6-bf57-43f0-bf77-d1f435cb8940" xlink:to="loc_us-gaap_PostretirementMedicalPlansWithPrescriptionDrugBenefitsAbstract_18e46edd-302d-4a4c-b95b-f47c03ff3c90" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrescriptionDrugSubsidyReceiptsNextTwelveMonths_aa98d0c9-24db-44ef-a356-248a6dd93c8c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PrescriptionDrugSubsidyReceiptsNextTwelveMonths"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PostretirementMedicalPlansWithPrescriptionDrugBenefitsAbstract_18e46edd-302d-4a4c-b95b-f47c03ff3c90" xlink:to="loc_us-gaap_PrescriptionDrugSubsidyReceiptsNextTwelveMonths_aa98d0c9-24db-44ef-a356-248a6dd93c8c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrescriptionDrugSubsidyReceiptsYearTwo1_914cf0d8-68f8-4e93-be2d-817be3b1cccd" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PrescriptionDrugSubsidyReceiptsYearTwo1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PostretirementMedicalPlansWithPrescriptionDrugBenefitsAbstract_18e46edd-302d-4a4c-b95b-f47c03ff3c90" xlink:to="loc_us-gaap_PrescriptionDrugSubsidyReceiptsYearTwo1_914cf0d8-68f8-4e93-be2d-817be3b1cccd" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrescriptionDrugSubsidyReceiptsYearThree1_87195ad6-d69b-4441-9755-86312c7e5236" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PrescriptionDrugSubsidyReceiptsYearThree1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PostretirementMedicalPlansWithPrescriptionDrugBenefitsAbstract_18e46edd-302d-4a4c-b95b-f47c03ff3c90" xlink:to="loc_us-gaap_PrescriptionDrugSubsidyReceiptsYearThree1_87195ad6-d69b-4441-9755-86312c7e5236" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrescriptionDrugSubsidyReceiptsYearFour1_e56cd59d-43da-40a2-9eb1-a60637e2f60e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PrescriptionDrugSubsidyReceiptsYearFour1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PostretirementMedicalPlansWithPrescriptionDrugBenefitsAbstract_18e46edd-302d-4a4c-b95b-f47c03ff3c90" xlink:to="loc_us-gaap_PrescriptionDrugSubsidyReceiptsYearFour1_e56cd59d-43da-40a2-9eb1-a60637e2f60e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrescriptionDrugSubsidyReceiptsYearFive1_95e2255b-6cd1-4ef6-9a7f-970f23b2e99c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PrescriptionDrugSubsidyReceiptsYearFive1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PostretirementMedicalPlansWithPrescriptionDrugBenefitsAbstract_18e46edd-302d-4a4c-b95b-f47c03ff3c90" xlink:to="loc_us-gaap_PrescriptionDrugSubsidyReceiptsYearFive1_95e2255b-6cd1-4ef6-9a7f-970f23b2e99c" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrescriptionDrugSubsidyReceiptsAfterYearFive_a02c268a-8e4a-4969-81db-b56a3ce3dc4b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PrescriptionDrugSubsidyReceiptsAfterYearFive"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PostretirementMedicalPlansWithPrescriptionDrugBenefitsAbstract_18e46edd-302d-4a4c-b95b-f47c03ff3c90" xlink:to="loc_us-gaap_PrescriptionDrugSubsidyReceiptsAfterYearFive_a02c268a-8e4a-4969-81db-b56a3ce3dc4b" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_DefinedBenefitPlansOfAffiliatesAbstract_68f6748f-efa6-4074-ab17-5181379347ca" xlink:href="nrg-20201231.xsd#nrg_DefinedBenefitPlansOfAffiliatesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_68bc56a6-bf57-43f0-bf77-d1f435cb8940" xlink:to="loc_nrg_DefinedBenefitPlansOfAffiliatesAbstract_68f6748f-efa6-4074-ab17-5181379347ca" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LimitedLiabilityCompanyLLCOrLimitedPartnershipLPMembersOrLimitedPartnersOwnershipInterest_e24ca2a1-1e1d-4f18-8ec9-423537b12fd4" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LimitedLiabilityCompanyLLCOrLimitedPartnershipLPMembersOrLimitedPartnersOwnershipInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_DefinedBenefitPlansOfAffiliatesAbstract_68f6748f-efa6-4074-ab17-5181379347ca" xlink:to="loc_us-gaap_LimitedLiabilityCompanyLLCOrLimitedPartnershipLPMembersOrLimitedPartnersOwnershipInterest_e24ca2a1-1e1d-4f18-8ec9-423537b12fd4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_PercentageOfContributionToRetirementPlanObligationsReimbursedByEntity_aba248b3-a574-4fdf-afbc-559e916d04ea" xlink:href="nrg-20201231.xsd#nrg_PercentageOfContributionToRetirementPlanObligationsReimbursedByEntity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_DefinedBenefitPlansOfAffiliatesAbstract_68f6748f-efa6-4074-ab17-5181379347ca" xlink:to="loc_nrg_PercentageOfContributionToRetirementPlanObligationsReimbursedByEntity_aba248b3-a574-4fdf-afbc-559e916d04ea" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanRecognizedNetGainLossDueToCurtailments_784c899b-f7bb-412d-9801-4ce2c6354cdf" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanRecognizedNetGainLossDueToCurtailments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_DefinedBenefitPlansOfAffiliatesAbstract_68f6748f-efa6-4074-ab17-5181379347ca" xlink:to="loc_us-gaap_DefinedBenefitPlanRecognizedNetGainLossDueToCurtailments_784c899b-f7bb-412d-9801-4ce2c6354cdf" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanCurtailments_b7797250-c132-47d7-a4e0-80723826190b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanCurtailments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_DefinedBenefitPlansOfAffiliatesAbstract_68f6748f-efa6-4074-ab17-5181379347ca" xlink:to="loc_us-gaap_DefinedBenefitPlanCurtailments_b7797250-c132-47d7-a4e0-80723826190b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_DefinedBenefitPlanAmountReimbursedToSponsor_d0badaa0-da7a-41b9-a652-80ee84863a22" xlink:href="nrg-20201231.xsd#nrg_DefinedBenefitPlanAmountReimbursedToSponsor"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_DefinedBenefitPlansOfAffiliatesAbstract_68f6748f-efa6-4074-ab17-5181379347ca" xlink:to="loc_nrg_DefinedBenefitPlanAmountReimbursedToSponsor_d0badaa0-da7a-41b9-a652-80ee84863a22" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_DefinedBenefitObligationReimbursementOfContributionToAffiliatesInNextFiscalYear_580ff068-0f15-434a-80fd-bcf141db7d5f" xlink:href="nrg-20201231.xsd#nrg_DefinedBenefitObligationReimbursementOfContributionToAffiliatesInNextFiscalYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_DefinedBenefitPlansOfAffiliatesAbstract_68f6748f-efa6-4074-ab17-5181379347ca" xlink:to="loc_nrg_DefinedBenefitObligationReimbursementOfContributionToAffiliatesInNextFiscalYear_580ff068-0f15-434a-80fd-bcf141db7d5f" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_AmountRecognizedInStatementOfFinancialPositionAndAccumulatedOtherComprehensiveIncomeRelatedToEquityMethodInvestmentAbstract_58cd0e10-73cc-46c8-aaf6-0e7274195979" xlink:href="nrg-20201231.xsd#nrg_AmountRecognizedInStatementOfFinancialPositionAndAccumulatedOtherComprehensiveIncomeRelatedToEquityMethodInvestmentAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_DefinedBenefitPlansOfAffiliatesAbstract_68f6748f-efa6-4074-ab17-5181379347ca" xlink:to="loc_nrg_AmountRecognizedInStatementOfFinancialPositionAndAccumulatedOtherComprehensiveIncomeRelatedToEquityMethodInvestmentAbstract_58cd0e10-73cc-46c8-aaf6-0e7274195979" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanFundedStatusOfPlan_ed88571c-94da-4451-b020-b4772aa0bc7d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanFundedStatusOfPlan"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_AmountRecognizedInStatementOfFinancialPositionAndAccumulatedOtherComprehensiveIncomeRelatedToEquityMethodInvestmentAbstract_58cd0e10-73cc-46c8-aaf6-0e7274195979" xlink:to="loc_us-gaap_DefinedBenefitPlanFundedStatusOfPlan_ed88571c-94da-4451-b020-b4772aa0bc7d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost_1d52decf-400d-412e-a924-e8bd6659fdfc" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_AmountRecognizedInStatementOfFinancialPositionAndAccumulatedOtherComprehensiveIncomeRelatedToEquityMethodInvestmentAbstract_58cd0e10-73cc-46c8-aaf6-0e7274195979" xlink:to="loc_us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost_1d52decf-400d-412e-a924-e8bd6659fdfc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeTax_404212e6-fd39-43e9-ac3a-255bc5ffae42" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_AmountRecognizedInStatementOfFinancialPositionAndAccumulatedOtherComprehensiveIncomeRelatedToEquityMethodInvestmentAbstract_58cd0e10-73cc-46c8-aaf6-0e7274195979" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeTax_404212e6-fd39-43e9-ac3a-255bc5ffae42" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_DefinedContributionPlansAbstract_3b87c3ed-288c-45ae-bb0f-cfceabeba757" xlink:href="nrg-20201231.xsd#nrg_DefinedContributionPlansAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_68bc56a6-bf57-43f0-bf77-d1f435cb8940" xlink:to="loc_nrg_DefinedContributionPlansAbstract_3b87c3ed-288c-45ae-bb0f-cfceabeba757" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedContributionPlanCostRecognized_f2f528ca-f770-4dad-bc3d-26a087097d79" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedContributionPlanCostRecognized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_DefinedContributionPlansAbstract_3b87c3ed-288c-45ae-bb0f-cfceabeba757" xlink:to="loc_us-gaap_DefinedContributionPlanCostRecognized_f2f528ca-f770-4dad-bc3d-26a087097d79" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_cf232578-a160-4e91-b26a-4666ee4b0c3e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_68bc56a6-bf57-43f0-bf77-d1f435cb8940" xlink:to="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_cf232578-a160-4e91-b26a-4666ee4b0c3e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipAxis_ca4fd810-00a1-4be3-8c13-9d3a20c374ad" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_OwnershipAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_cf232578-a160-4e91-b26a-4666ee4b0c3e" xlink:to="loc_srt_OwnershipAxis_ca4fd810-00a1-4be3-8c13-9d3a20c374ad" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipDomain_ca4fd810-00a1-4be3-8c13-9d3a20c374ad_default" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_OwnershipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_OwnershipAxis_ca4fd810-00a1-4be3-8c13-9d3a20c374ad" xlink:to="loc_srt_OwnershipDomain_ca4fd810-00a1-4be3-8c13-9d3a20c374ad_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipDomain_59b6f978-ff12-4558-9724-ca94f5698ab3" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_OwnershipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_OwnershipAxis_ca4fd810-00a1-4be3-8c13-9d3a20c374ad" xlink:to="loc_srt_OwnershipDomain_59b6f978-ff12-4558-9724-ca94f5698ab3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_SouthTexasProjectUnits1And2Member_92e63902-4a3f-4ca7-9b5b-a818a2b2f7cb" xlink:href="nrg-20201231.xsd#nrg_SouthTexasProjectUnits1And2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_OwnershipDomain_59b6f978-ff12-4558-9724-ca94f5698ab3" xlink:to="loc_nrg_SouthTexasProjectUnits1And2Member_92e63902-4a3f-4ca7-9b5b-a818a2b2f7cb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTypeAxis_745da6d9-fd84-4d11-b23b-33b60b64d7d1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RetirementPlanTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_cf232578-a160-4e91-b26a-4666ee4b0c3e" xlink:to="loc_us-gaap_RetirementPlanTypeAxis_745da6d9-fd84-4d11-b23b-33b60b64d7d1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTypeDomain_745da6d9-fd84-4d11-b23b-33b60b64d7d1_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RetirementPlanTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RetirementPlanTypeAxis_745da6d9-fd84-4d11-b23b-33b60b64d7d1" xlink:to="loc_us-gaap_RetirementPlanTypeDomain_745da6d9-fd84-4d11-b23b-33b60b64d7d1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTypeDomain_fae6279a-583c-4d64-9734-7947473c9342" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RetirementPlanTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RetirementPlanTypeAxis_745da6d9-fd84-4d11-b23b-33b60b64d7d1" xlink:to="loc_us-gaap_RetirementPlanTypeDomain_fae6279a-583c-4d64-9734-7947473c9342" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PensionPlansDefinedBenefitMember_2d03346e-6a2d-40d6-9b70-289d822fd198" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PensionPlansDefinedBenefitMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RetirementPlanTypeDomain_fae6279a-583c-4d64-9734-7947473c9342" xlink:to="loc_us-gaap_PensionPlansDefinedBenefitMember_2d03346e-6a2d-40d6-9b70-289d822fd198" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember_f3a9e6d5-5af8-4837-acee-04d4a4669954" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RetirementPlanTypeDomain_fae6279a-583c-4d64-9734-7947473c9342" xlink:to="loc_us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember_f3a9e6d5-5af8-4837-acee-04d4a4669954" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_JointlyOwnedUtilityPlantAxis_3cf57a3b-eed8-42a9-9d7b-47fa079201e6" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_JointlyOwnedUtilityPlantAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_cf232578-a160-4e91-b26a-4666ee4b0c3e" xlink:to="loc_us-gaap_JointlyOwnedUtilityPlantAxis_3cf57a3b-eed8-42a9-9d7b-47fa079201e6" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_JointlyOwnedUtilityPlantDomain_3cf57a3b-eed8-42a9-9d7b-47fa079201e6_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_JointlyOwnedUtilityPlantDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_JointlyOwnedUtilityPlantAxis_3cf57a3b-eed8-42a9-9d7b-47fa079201e6" xlink:to="loc_us-gaap_JointlyOwnedUtilityPlantDomain_3cf57a3b-eed8-42a9-9d7b-47fa079201e6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_JointlyOwnedUtilityPlantDomain_add29d73-256f-4f6a-ba02-4e47d80d3148" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_JointlyOwnedUtilityPlantDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_JointlyOwnedUtilityPlantAxis_3cf57a3b-eed8-42a9-9d7b-47fa079201e6" xlink:to="loc_us-gaap_JointlyOwnedUtilityPlantDomain_add29d73-256f-4f6a-ba02-4e47d80d3148" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_SouthTexasProjectUnits1And2Member_f0d4c2c0-de1c-4df7-aecb-1f8dd9a7549d" xlink:href="nrg-20201231.xsd#nrg_SouthTexasProjectUnits1And2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_JointlyOwnedUtilityPlantDomain_add29d73-256f-4f6a-ba02-4e47d80d3148" xlink:to="loc_nrg_SouthTexasProjectUnits1And2Member_f0d4c2c0-de1c-4df7-aecb-1f8dd9a7549d" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/CapitalStructure" xlink:type="simple" xlink:href="nrg-20201231.xsd#CapitalStructure"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/CapitalStructure" xlink:type="extended" id="i5c65bc9db6e04eeb908c08a00ef1abf1_CapitalStructure"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/CapitalStructureTables" xlink:type="simple" xlink:href="nrg-20201231.xsd#CapitalStructureTables"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/CapitalStructureTables" xlink:type="extended" id="ie5e1c287ad6c4c4588e855c0e52b9edf_CapitalStructureTables"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/CapitalStructureChangesinCommonSharesissuedandOutstandingDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#CapitalStructureChangesinCommonSharesissuedandOutstandingDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/CapitalStructureChangesinCommonSharesissuedandOutstandingDetails" xlink:type="extended" id="ie8a16f2658fe40a9bee2c2f28be6919a_CapitalStructureChangesinCommonSharesissuedandOutstandingDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfCapitalizationLineItems_787e0a95-0708-43d9-8909-d82e05e241d7" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfCapitalizationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TemporaryEquitySharesAuthorized_a89477f3-bddb-4d8f-8550-ffc3220eea74" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TemporaryEquitySharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfCapitalizationLineItems_787e0a95-0708-43d9-8909-d82e05e241d7" xlink:to="loc_us-gaap_TemporaryEquitySharesAuthorized_a89477f3-bddb-4d8f-8550-ffc3220eea74" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesAuthorized_3aa7fb1b-deeb-41e9-8392-b5ed8a146271" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommonStockSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfCapitalizationLineItems_787e0a95-0708-43d9-8909-d82e05e241d7" xlink:to="loc_us-gaap_CommonStockSharesAuthorized_3aa7fb1b-deeb-41e9-8392-b5ed8a146271" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_4e6010f9-55c4-4c72-94cc-c7a889ea0ad4" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfCapitalizationLineItems_787e0a95-0708-43d9-8909-d82e05e241d7" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_4e6010f9-55c4-4c72-94cc-c7a889ea0ad4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesIssued_c14c214d-65cf-4435-8dbc-18f34db15a25" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommonStockSharesIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_4e6010f9-55c4-4c72-94cc-c7a889ea0ad4" xlink:to="loc_us-gaap_CommonStockSharesIssued_c14c214d-65cf-4435-8dbc-18f34db15a25" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockShares_c42e6541-14e4-4d6c-82c4-1789e55b4e8d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TreasuryStockShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_4e6010f9-55c4-4c72-94cc-c7a889ea0ad4" xlink:to="loc_us-gaap_TreasuryStockShares_c42e6541-14e4-4d6c-82c4-1789e55b4e8d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_4c57bfc3-33cf-4c18-ad6f-ef736bd9cd66" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_4e6010f9-55c4-4c72-94cc-c7a889ea0ad4" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_4c57bfc3-33cf-4c18-ad6f-ef736bd9cd66" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans_09d831bc-61cd-457a-b880-e552263df824" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_4e6010f9-55c4-4c72-94cc-c7a889ea0ad4" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans_09d831bc-61cd-457a-b880-e552263df824" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation_25b4599a-cb4c-4bd6-8969-3033a13ad49b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_4e6010f9-55c4-4c72-94cc-c7a889ea0ad4" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation_25b4599a-cb4c-4bd6-8969-3033a13ad49b" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedDuringPeriodShares_0bfb6062-d662-4e4e-949c-7eddf5b61b42" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockRepurchasedDuringPeriodShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_4e6010f9-55c4-4c72-94cc-c7a889ea0ad4" xlink:to="loc_us-gaap_StockRepurchasedDuringPeriodShares_0bfb6062-d662-4e4e-949c-7eddf5b61b42" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesIssued_241bbd96-8296-45cb-b44e-e0ab8ed3e575" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommonStockSharesIssued"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockShares_66075a4a-7f5f-461f-a939-62e87b5f4318" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TreasuryStockShares"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_5ee27d10-3541-4d98-a87a-732918fb0d84" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfCapitalizationTable_962b15a9-7225-47fe-a932-4ab9b7a52108" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfCapitalizationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfCapitalizationLineItems_787e0a95-0708-43d9-8909-d82e05e241d7" xlink:to="loc_us-gaap_ScheduleOfCapitalizationTable_962b15a9-7225-47fe-a932-4ab9b7a52108" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_45fb14c9-040b-4a35-ad3c-4b42bce3a97c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfCapitalizationTable_962b15a9-7225-47fe-a932-4ab9b7a52108" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_45fb14c9-040b-4a35-ad3c-4b42bce3a97c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_45fb14c9-040b-4a35-ad3c-4b42bce3a97c_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_45fb14c9-040b-4a35-ad3c-4b42bce3a97c" xlink:to="loc_us-gaap_EquityComponentDomain_45fb14c9-040b-4a35-ad3c-4b42bce3a97c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_cb9312ff-e017-4f77-8753-6059399b1fc1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_45fb14c9-040b-4a35-ad3c-4b42bce3a97c" xlink:to="loc_us-gaap_EquityComponentDomain_cb9312ff-e017-4f77-8753-6059399b1fc1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_dcff961c-d5ac-4a0c-a9df-5135d233ed10" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_cb9312ff-e017-4f77-8753-6059399b1fc1" xlink:to="loc_us-gaap_CommonStockMember_dcff961c-d5ac-4a0c-a9df-5135d233ed10" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockMember_c679bb61-49ee-44f0-af80-ae012febb973" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TreasuryStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_cb9312ff-e017-4f77-8753-6059399b1fc1" xlink:to="loc_us-gaap_TreasuryStockMember_c679bb61-49ee-44f0-af80-ae012febb973" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/CapitalStructureCommonStockDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#CapitalStructureCommonStockDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/CapitalStructureCommonStockDetails" xlink:type="extended" id="i7f826698bcda4cca907e7b236ca47ecc_CapitalStructureCommonStockDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityClassOfTreasuryStockLineItems_891c47c7-54db-471b-b0aa-e55b028cf3ee" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityClassOfTreasuryStockLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockCapitalSharesReservedForFutureIssuance_a3856fef-edb8-409e-bfe4-8d7d8726a277" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommonStockCapitalSharesReservedForFutureIssuance"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityClassOfTreasuryStockLineItems_891c47c7-54db-471b-b0aa-e55b028cf3ee" xlink:to="loc_us-gaap_CommonStockCapitalSharesReservedForFutureIssuance_a3856fef-edb8-409e-bfe4-8d7d8726a277" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_CommonStockQuarterlyDividendsPerShareCashPaid_76a890a7-941e-48a9-9d81-f66ca75729b1" xlink:href="nrg-20201231.xsd#nrg_CommonStockQuarterlyDividendsPerShareCashPaid"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityClassOfTreasuryStockLineItems_891c47c7-54db-471b-b0aa-e55b028cf3ee" xlink:to="loc_nrg_CommonStockQuarterlyDividendsPerShareCashPaid_76a890a7-941e-48a9-9d81-f66ca75729b1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockDividendsPerShareCashPaid_669dc316-d357-469c-837d-d8befe278962" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommonStockDividendsPerShareCashPaid"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityClassOfTreasuryStockLineItems_891c47c7-54db-471b-b0aa-e55b028cf3ee" xlink:to="loc_us-gaap_CommonStockDividendsPerShareCashPaid_669dc316-d357-469c-837d-d8befe278962" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_CommonStockDividendsProposedAnnualAmountPerShare_b75e7067-b662-441c-a77a-6a41cefdb111" xlink:href="nrg-20201231.xsd#nrg_CommonStockDividendsProposedAnnualAmountPerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityClassOfTreasuryStockLineItems_891c47c7-54db-471b-b0aa-e55b028cf3ee" xlink:to="loc_nrg_CommonStockDividendsProposedAnnualAmountPerShare_b75e7067-b662-441c-a77a-6a41cefdb111" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_LongTermCapitalAllocationTargetAllocationCashGeneratedAllocatedToGrowthInvestmentsPercentage_9416584f-7ace-4384-9f43-0e8982aff022" xlink:href="nrg-20201231.xsd#nrg_LongTermCapitalAllocationTargetAllocationCashGeneratedAllocatedToGrowthInvestmentsPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityClassOfTreasuryStockLineItems_891c47c7-54db-471b-b0aa-e55b028cf3ee" xlink:to="loc_nrg_LongTermCapitalAllocationTargetAllocationCashGeneratedAllocatedToGrowthInvestmentsPercentage_9416584f-7ace-4384-9f43-0e8982aff022" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_LongTermCapitalAllocationTargetAllocationCashGeneratedAllocatedReturnedToShareholdersPercentage_ec218702-3ea0-4e6d-90ca-0b2f095d2ed7" xlink:href="nrg-20201231.xsd#nrg_LongTermCapitalAllocationTargetAllocationCashGeneratedAllocatedReturnedToShareholdersPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityClassOfTreasuryStockLineItems_891c47c7-54db-471b-b0aa-e55b028cf3ee" xlink:to="loc_nrg_LongTermCapitalAllocationTargetAllocationCashGeneratedAllocatedReturnedToShareholdersPercentage_ec218702-3ea0-4e6d-90ca-0b2f095d2ed7" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_CommonStockAnnualDividendGrowthRate_e893ee66-1de1-4cb0-8f12-20a4495d06d5" xlink:href="nrg-20201231.xsd#nrg_CommonStockAnnualDividendGrowthRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityClassOfTreasuryStockLineItems_891c47c7-54db-471b-b0aa-e55b028cf3ee" xlink:to="loc_nrg_CommonStockAnnualDividendGrowthRate_e893ee66-1de1-4cb0-8f12-20a4495d06d5" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_CommonStockAnnualDividendsIncreaseDecreasePercentage_d492f100-924a-45ea-ab2b-e492b73ceed9" xlink:href="nrg-20201231.xsd#nrg_CommonStockAnnualDividendsIncreaseDecreasePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityClassOfTreasuryStockLineItems_891c47c7-54db-471b-b0aa-e55b028cf3ee" xlink:to="loc_nrg_CommonStockAnnualDividendsIncreaseDecreasePercentage_d492f100-924a-45ea-ab2b-e492b73ceed9" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockDividendsPerShareDeclared_b13680b4-5f3e-4cb2-a53b-8b555c68c6c5" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommonStockDividendsPerShareDeclared"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityClassOfTreasuryStockLineItems_891c47c7-54db-471b-b0aa-e55b028cf3ee" xlink:to="loc_us-gaap_CommonStockDividendsPerShareDeclared_b13680b4-5f3e-4cb2-a53b-8b555c68c6c5" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_EmployeeStockPurchasePlanMinimumPercentageofCompensationEligible_b0dc52ae-2879-43fb-9715-8d16f157362a" xlink:href="nrg-20201231.xsd#nrg_EmployeeStockPurchasePlanMinimumPercentageofCompensationEligible"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityClassOfTreasuryStockLineItems_891c47c7-54db-471b-b0aa-e55b028cf3ee" xlink:to="loc_nrg_EmployeeStockPurchasePlanMinimumPercentageofCompensationEligible_b0dc52ae-2879-43fb-9715-8d16f157362a" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_EmployeeStockPurchasePlanMaximumPercentageOfCompensationEligible_230cd0bd-e3bf-4a57-bef4-5e1c3f37be1f" xlink:href="nrg-20201231.xsd#nrg_EmployeeStockPurchasePlanMaximumPercentageOfCompensationEligible"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityClassOfTreasuryStockLineItems_891c47c7-54db-471b-b0aa-e55b028cf3ee" xlink:to="loc_nrg_EmployeeStockPurchasePlanMaximumPercentageOfCompensationEligible_230cd0bd-e3bf-4a57-bef4-5e1c3f37be1f" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardDiscountFromMarketPricePurchaseDate_142011ee-6c3b-46e2-902f-3316c8f37883" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardDiscountFromMarketPricePurchaseDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityClassOfTreasuryStockLineItems_891c47c7-54db-471b-b0aa-e55b028cf3ee" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardDiscountFromMarketPricePurchaseDate_142011ee-6c3b-46e2-902f-3316c8f37883" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_EmployeeStockPurchasePlanExercisePriceAsPercentageOfFairValue_67305fde-efc6-44fa-abc2-a03c4d27d38e" xlink:href="nrg-20201231.xsd#nrg_EmployeeStockPurchasePlanExercisePriceAsPercentageOfFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityClassOfTreasuryStockLineItems_891c47c7-54db-471b-b0aa-e55b028cf3ee" xlink:to="loc_nrg_EmployeeStockPurchasePlanExercisePriceAsPercentageOfFairValue_67305fde-efc6-44fa-abc2-a03c4d27d38e" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_CommonStockCapitalSharesReservedForEmployeeStockPurchasePlan_3611bbf6-d058-427a-9004-ca4795beef39" xlink:href="nrg-20201231.xsd#nrg_CommonStockCapitalSharesReservedForEmployeeStockPurchasePlan"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityClassOfTreasuryStockLineItems_891c47c7-54db-471b-b0aa-e55b028cf3ee" xlink:to="loc_nrg_CommonStockCapitalSharesReservedForEmployeeStockPurchasePlan_3611bbf6-d058-427a-9004-ca4795beef39" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchaseProgramAuthorizedAmount1_5d0a1c24-ad07-470e-a3f8-6a973dcdd378" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockRepurchaseProgramAuthorizedAmount1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityClassOfTreasuryStockLineItems_891c47c7-54db-471b-b0aa-e55b028cf3ee" xlink:to="loc_us-gaap_StockRepurchaseProgramAuthorizedAmount1_5d0a1c24-ad07-470e-a3f8-6a973dcdd378" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedDuringPeriodShares_194ab831-5cd0-4699-9784-2597226b7888" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockRepurchasedDuringPeriodShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityClassOfTreasuryStockLineItems_891c47c7-54db-471b-b0aa-e55b028cf3ee" xlink:to="loc_us-gaap_StockRepurchasedDuringPeriodShares_194ab831-5cd0-4699-9784-2597226b7888" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfTreasuryStockTable_6d9dded0-24c0-475b-ba2d-f21648d08dd5" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ClassOfTreasuryStockTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_EquityClassOfTreasuryStockLineItems_891c47c7-54db-471b-b0aa-e55b028cf3ee" xlink:to="loc_us-gaap_ClassOfTreasuryStockTable_6d9dded0-24c0-475b-ba2d-f21648d08dd5" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_550e89e2-e6d5-42ee-a5dd-cdb3bb28232d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ClassOfTreasuryStockTable_6d9dded0-24c0-475b-ba2d-f21648d08dd5" xlink:to="loc_us-gaap_FinancialInstrumentAxis_550e89e2-e6d5-42ee-a5dd-cdb3bb28232d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_550e89e2-e6d5-42ee-a5dd-cdb3bb28232d_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_550e89e2-e6d5-42ee-a5dd-cdb3bb28232d" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_550e89e2-e6d5-42ee-a5dd-cdb3bb28232d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_369f86aa-948f-436a-9281-9396dffd1b58" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_550e89e2-e6d5-42ee-a5dd-cdb3bb28232d" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_369f86aa-948f-436a-9281-9396dffd1b58" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockCompensationPlanMember_e4cf3b18-e218-4d4a-ac32-a4c1fd999166" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockCompensationPlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_369f86aa-948f-436a-9281-9396dffd1b58" xlink:to="loc_us-gaap_StockCompensationPlanMember_e4cf3b18-e218-4d4a-ac32-a4c1fd999166" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_c8df27d8-2f91-49ee-b82d-adca464fbf36" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ClassOfTreasuryStockTable_6d9dded0-24c0-475b-ba2d-f21648d08dd5" xlink:to="loc_srt_RangeAxis_c8df27d8-2f91-49ee-b82d-adca464fbf36" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_c8df27d8-2f91-49ee-b82d-adca464fbf36_default" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_c8df27d8-2f91-49ee-b82d-adca464fbf36" xlink:to="loc_srt_RangeMember_c8df27d8-2f91-49ee-b82d-adca464fbf36_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_18d7e7f2-a869-4497-b15e-6dde50861e75" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_c8df27d8-2f91-49ee-b82d-adca464fbf36" xlink:to="loc_srt_RangeMember_18d7e7f2-a869-4497-b15e-6dde50861e75" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_5607b5bf-f3a2-479d-8b61-3290131ded22" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_18d7e7f2-a869-4497-b15e-6dde50861e75" xlink:to="loc_srt_MinimumMember_5607b5bf-f3a2-479d-8b61-3290131ded22" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_0c8fa4d4-7b07-4ccd-91a6-c00eb2d6318d" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_18d7e7f2-a869-4497-b15e-6dde50861e75" xlink:to="loc_srt_MaximumMember_0c8fa4d4-7b07-4ccd-91a6-c00eb2d6318d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementScenarioAxis_39a138b1-4f05-4103-87b4-3b021c3d6810" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_StatementScenarioAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ClassOfTreasuryStockTable_6d9dded0-24c0-475b-ba2d-f21648d08dd5" xlink:to="loc_srt_StatementScenarioAxis_39a138b1-4f05-4103-87b4-3b021c3d6810" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_39a138b1-4f05-4103-87b4-3b021c3d6810_default" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ScenarioUnspecifiedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementScenarioAxis_39a138b1-4f05-4103-87b4-3b021c3d6810" xlink:to="loc_srt_ScenarioUnspecifiedDomain_39a138b1-4f05-4103-87b4-3b021c3d6810_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_cdb5e6f7-31ab-4ee5-9b53-1def4f8304f6" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ScenarioUnspecifiedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementScenarioAxis_39a138b1-4f05-4103-87b4-3b021c3d6810" xlink:to="loc_srt_ScenarioUnspecifiedDomain_cdb5e6f7-31ab-4ee5-9b53-1def4f8304f6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScenarioPlanMember_dc9bb2b1-cb8e-43e6-a6b2-4761e6d16cb6" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScenarioPlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ScenarioUnspecifiedDomain_cdb5e6f7-31ab-4ee5-9b53-1def4f8304f6" xlink:to="loc_us-gaap_ScenarioPlanMember_dc9bb2b1-cb8e-43e6-a6b2-4761e6d16cb6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_aaf73d8e-1765-4f55-8537-2bb818329881" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ClassOfTreasuryStockTable_6d9dded0-24c0-475b-ba2d-f21648d08dd5" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_aaf73d8e-1765-4f55-8537-2bb818329881" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_aaf73d8e-1765-4f55-8537-2bb818329881_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_aaf73d8e-1765-4f55-8537-2bb818329881" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_aaf73d8e-1765-4f55-8537-2bb818329881_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_b2af245b-1c53-4d8e-b734-3dff87d4e3a6" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_aaf73d8e-1765-4f55-8537-2bb818329881" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_b2af245b-1c53-4d8e-b734-3dff87d4e3a6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_0ef28450-ae1b-4417-81e2-66df837d765e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_b2af245b-1c53-4d8e-b734-3dff87d4e3a6" xlink:to="loc_us-gaap_SubsequentEventMember_0ef28450-ae1b-4417-81e2-66df837d765e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_CapitalAllocationPlanAxis_26994ee6-993c-4ab7-9a73-9b2c1cd6da3d" xlink:href="nrg-20201231.xsd#nrg_CapitalAllocationPlanAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ClassOfTreasuryStockTable_6d9dded0-24c0-475b-ba2d-f21648d08dd5" xlink:to="loc_nrg_CapitalAllocationPlanAxis_26994ee6-993c-4ab7-9a73-9b2c1cd6da3d" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_CapitalAllocationPlanDomain_26994ee6-993c-4ab7-9a73-9b2c1cd6da3d_default" xlink:href="nrg-20201231.xsd#nrg_CapitalAllocationPlanDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_nrg_CapitalAllocationPlanAxis_26994ee6-993c-4ab7-9a73-9b2c1cd6da3d" xlink:to="loc_nrg_CapitalAllocationPlanDomain_26994ee6-993c-4ab7-9a73-9b2c1cd6da3d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_CapitalAllocationPlanDomain_ac56a1d1-5dab-4d3c-a2fe-285998b5c3e4" xlink:href="nrg-20201231.xsd#nrg_CapitalAllocationPlanDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_nrg_CapitalAllocationPlanAxis_26994ee6-993c-4ab7-9a73-9b2c1cd6da3d" xlink:to="loc_nrg_CapitalAllocationPlanDomain_ac56a1d1-5dab-4d3c-a2fe-285998b5c3e4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_CapitalAllocationPlanMember_03e7cb89-ed3d-429d-8033-38709d5335cc" xlink:href="nrg-20201231.xsd#nrg_CapitalAllocationPlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_CapitalAllocationPlanDomain_ac56a1d1-5dab-4d3c-a2fe-285998b5c3e4" xlink:to="loc_nrg_CapitalAllocationPlanMember_03e7cb89-ed3d-429d-8033-38709d5335cc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_A2018CapitalAllocationPlanMember_d1fa301c-a9c9-45b5-bb9c-02c468d22a06" xlink:href="nrg-20201231.xsd#nrg_A2018CapitalAllocationPlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_CapitalAllocationPlanDomain_ac56a1d1-5dab-4d3c-a2fe-285998b5c3e4" xlink:to="loc_nrg_A2018CapitalAllocationPlanMember_d1fa301c-a9c9-45b5-bb9c-02c468d22a06" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_A2019CapitalAllocationPlanMember_eb8b2a48-8f25-4643-9ef1-90a211922260" xlink:href="nrg-20201231.xsd#nrg_A2019CapitalAllocationPlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_CapitalAllocationPlanDomain_ac56a1d1-5dab-4d3c-a2fe-285998b5c3e4" xlink:to="loc_nrg_A2019CapitalAllocationPlanMember_eb8b2a48-8f25-4643-9ef1-90a211922260" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/CapitalStructureSummaryofChangesinSharesRepurchasedDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#CapitalStructureSummaryofChangesinSharesRepurchasedDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/CapitalStructureSummaryofChangesinSharesRepurchasedDetails" xlink:type="extended" id="id51dc90eb8344270989572aefffa64b5_CapitalStructureSummaryofChangesinSharesRepurchasedDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfCapitalizationEquityLineItems_f0cda2bf-aee1-446e-8171-83ba0150921f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfCapitalizationEquityLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedDuringPeriodShares_6e1992fe-4eba-420c-b084-328a5e5c58a6" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockRepurchasedDuringPeriodShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfCapitalizationEquityLineItems_f0cda2bf-aee1-446e-8171-83ba0150921f" xlink:to="loc_us-gaap_StockRepurchasedDuringPeriodShares_6e1992fe-4eba-420c-b084-328a5e5c58a6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockAcquiredAverageCostPerShare_e81c8ccd-3e9c-47cd-bc11-e9683581384a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TreasuryStockAcquiredAverageCostPerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfCapitalizationEquityLineItems_f0cda2bf-aee1-446e-8171-83ba0150921f" xlink:to="loc_us-gaap_TreasuryStockAcquiredAverageCostPerShare_e81c8ccd-3e9c-47cd-bc11-e9683581384a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedDuringPeriodValue_6ce60cd7-58c9-49cd-b0e4-76e9b1ca0901" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockRepurchasedDuringPeriodValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfCapitalizationEquityLineItems_f0cda2bf-aee1-446e-8171-83ba0150921f" xlink:to="loc_us-gaap_StockRepurchasedDuringPeriodValue_6ce60cd7-58c9-49cd-b0e4-76e9b1ca0901" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfCapitalizationEquityTable_683a8957-97d5-48a6-898a-69fe31350883" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfCapitalizationEquityTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfCapitalizationEquityLineItems_f0cda2bf-aee1-446e-8171-83ba0150921f" xlink:to="loc_us-gaap_ScheduleOfCapitalizationEquityTable_683a8957-97d5-48a6-898a-69fe31350883" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_CapitalAllocationPlanAxis_dcf6bd3c-c111-4d6e-9dbb-21d74a5dad4d" xlink:href="nrg-20201231.xsd#nrg_CapitalAllocationPlanAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfCapitalizationEquityTable_683a8957-97d5-48a6-898a-69fe31350883" xlink:to="loc_nrg_CapitalAllocationPlanAxis_dcf6bd3c-c111-4d6e-9dbb-21d74a5dad4d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_CapitalAllocationPlanDomain_dcf6bd3c-c111-4d6e-9dbb-21d74a5dad4d_default" xlink:href="nrg-20201231.xsd#nrg_CapitalAllocationPlanDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_nrg_CapitalAllocationPlanAxis_dcf6bd3c-c111-4d6e-9dbb-21d74a5dad4d" xlink:to="loc_nrg_CapitalAllocationPlanDomain_dcf6bd3c-c111-4d6e-9dbb-21d74a5dad4d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_CapitalAllocationPlanDomain_c955c03a-4801-4797-bcae-274de3e80244" xlink:href="nrg-20201231.xsd#nrg_CapitalAllocationPlanDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_nrg_CapitalAllocationPlanAxis_dcf6bd3c-c111-4d6e-9dbb-21d74a5dad4d" xlink:to="loc_nrg_CapitalAllocationPlanDomain_c955c03a-4801-4797-bcae-274de3e80244" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_CapitalAllocationPlanAcceleratedRepurchaseAgreementMay2018Member_28a9444a-8040-4a6e-9255-b60f078fd2ad" xlink:href="nrg-20201231.xsd#nrg_CapitalAllocationPlanAcceleratedRepurchaseAgreementMay2018Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_CapitalAllocationPlanDomain_c955c03a-4801-4797-bcae-274de3e80244" xlink:to="loc_nrg_CapitalAllocationPlanAcceleratedRepurchaseAgreementMay2018Member_28a9444a-8040-4a6e-9255-b60f078fd2ad" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_CapitalAllocationPlanAcceleratedRepurchaseProgramSeptember2018Member_50e850a2-3c94-4519-973b-17f69ba47b5d" xlink:href="nrg-20201231.xsd#nrg_CapitalAllocationPlanAcceleratedRepurchaseProgramSeptember2018Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_CapitalAllocationPlanDomain_c955c03a-4801-4797-bcae-274de3e80244" xlink:to="loc_nrg_CapitalAllocationPlanAcceleratedRepurchaseProgramSeptember2018Member_50e850a2-3c94-4519-973b-17f69ba47b5d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_CapitalAllocationPlanOpenMarketRepurchasesMember_c3bd74d3-b3fe-483e-bceb-4439a6f2153d" xlink:href="nrg-20201231.xsd#nrg_CapitalAllocationPlanOpenMarketRepurchasesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_CapitalAllocationPlanDomain_c955c03a-4801-4797-bcae-274de3e80244" xlink:to="loc_nrg_CapitalAllocationPlanOpenMarketRepurchasesMember_c3bd74d3-b3fe-483e-bceb-4439a6f2153d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_CapitalAllocationPlanAcceleratedRepurchaseAgreementFebruaryMember_7b53de92-7276-4238-bd8a-b37d46d1ed0f" xlink:href="nrg-20201231.xsd#nrg_CapitalAllocationPlanAcceleratedRepurchaseAgreementFebruaryMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_CapitalAllocationPlanDomain_c955c03a-4801-4797-bcae-274de3e80244" xlink:to="loc_nrg_CapitalAllocationPlanAcceleratedRepurchaseAgreementFebruaryMember_7b53de92-7276-4238-bd8a-b37d46d1ed0f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_EquivalentSharesInLieuOfTaxWithholdingOnEquityCompensationIssuancesMember_9562a4ee-3c84-4e40-9f83-40b0f7456f9e" xlink:href="nrg-20201231.xsd#nrg_EquivalentSharesInLieuOfTaxWithholdingOnEquityCompensationIssuancesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_CapitalAllocationPlanDomain_c955c03a-4801-4797-bcae-274de3e80244" xlink:to="loc_nrg_EquivalentSharesInLieuOfTaxWithholdingOnEquityCompensationIssuancesMember_9562a4ee-3c84-4e40-9f83-40b0f7456f9e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_CapitalAllocationPlanMember_71b16a23-0fb6-4515-aedc-a27439ee69a4" xlink:href="nrg-20201231.xsd#nrg_CapitalAllocationPlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_CapitalAllocationPlanDomain_c955c03a-4801-4797-bcae-274de3e80244" xlink:to="loc_nrg_CapitalAllocationPlanMember_71b16a23-0fb6-4515-aedc-a27439ee69a4" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/InvestmentsAccountedforbytheEquityMethodandVariableInterestEntities" xlink:type="simple" xlink:href="nrg-20201231.xsd#InvestmentsAccountedforbytheEquityMethodandVariableInterestEntities"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/InvestmentsAccountedforbytheEquityMethodandVariableInterestEntities" xlink:type="extended" id="i3dd386bd642d4ae99a433fa9dd3a95d9_InvestmentsAccountedforbytheEquityMethodandVariableInterestEntities"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/InvestmentsAccountedforbytheEquityMethodandVariableInterestEntitiesTables" xlink:type="simple" xlink:href="nrg-20201231.xsd#InvestmentsAccountedforbytheEquityMethodandVariableInterestEntitiesTables"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/InvestmentsAccountedforbytheEquityMethodandVariableInterestEntitiesTables" xlink:type="extended" id="ib21a6af51ddc415bbf8292e75a5c009f_InvestmentsAccountedforbytheEquityMethodandVariableInterestEntitiesTables"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/InvestmentsAccountedforbytheEquityMethodandVariableInterestEntitiesSummaryofEquityMethodInvestmentsDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#InvestmentsAccountedforbytheEquityMethodandVariableInterestEntitiesSummaryofEquityMethodInvestmentsDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/InvestmentsAccountedforbytheEquityMethodandVariableInterestEntitiesSummaryofEquityMethodInvestmentsDetails" xlink:type="extended" id="i3e1be138ada64ad682a64aac04e63799_InvestmentsAccountedforbytheEquityMethodandVariableInterestEntitiesSummaryofEquityMethodInvestmentsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_ac0072fb-9b9c-4182-bc19-bd6e345e0a6b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_77d6784e-686e-4c87-9470-beacd4b7ec1f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityMethodInvestmentOwnershipPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_ac0072fb-9b9c-4182-bc19-bd6e345e0a6b" xlink:to="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_77d6784e-686e-4c87-9470-beacd4b7ec1f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestments_b4e0c9f1-247c-4e8e-b32b-244a43448579" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_ac0072fb-9b9c-4182-bc19-bd6e345e0a6b" xlink:to="loc_us-gaap_EquityMethodInvestments_b4e0c9f1-247c-4e8e-b32b-244a43448579" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentDifferenceBetweenCarryingAmountAndUnderlyingEquity_b3f8fb9e-2fb0-4fce-b617-556caae9ae46" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityMethodInvestmentDifferenceBetweenCarryingAmountAndUnderlyingEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_ac0072fb-9b9c-4182-bc19-bd6e345e0a6b" xlink:to="loc_us-gaap_EquityMethodInvestmentDifferenceBetweenCarryingAmountAndUnderlyingEquity_b3f8fb9e-2fb0-4fce-b617-556caae9ae46" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsUndistributedEarningsFromEquityMethodInvestees_16d48e01-63e4-4158-9ccb-353d4f3d52f8" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RetainedEarningsUndistributedEarningsFromEquityMethodInvestees"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_ac0072fb-9b9c-4182-bc19-bd6e345e0a6b" xlink:to="loc_us-gaap_RetainedEarningsUndistributedEarningsFromEquityMethodInvestees_16d48e01-63e4-4158-9ccb-353d4f3d52f8" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_9aa5caed-1ffb-4570-b7e2-813a540aead1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_ac0072fb-9b9c-4182-bc19-bd6e345e0a6b" xlink:to="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_9aa5caed-1ffb-4570-b7e2-813a540aead1" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_92366125-25e9-4a77-8c61-faefaaf6b427" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_9aa5caed-1ffb-4570-b7e2-813a540aead1" xlink:to="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_92366125-25e9-4a77-8c61-faefaaf6b427" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_92366125-25e9-4a77-8c61-faefaaf6b427_default" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_92366125-25e9-4a77-8c61-faefaaf6b427" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_92366125-25e9-4a77-8c61-faefaaf6b427_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_b130119b-4529-4ea7-ac56-83da28ae669c" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_92366125-25e9-4a77-8c61-faefaaf6b427" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_b130119b-4529-4ea7-ac56-83da28ae669c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_AguaCalienteMember_c18cb33b-0001-4f65-9c6b-c170e500fc03" xlink:href="nrg-20201231.xsd#nrg_AguaCalienteMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_b130119b-4529-4ea7-ac56-83da28ae669c" xlink:to="loc_nrg_AguaCalienteMember_c18cb33b-0001-4f65-9c6b-c170e500fc03" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_GladstonePowerStationMember_3538beb7-c56f-4121-869b-2131b994d320" xlink:href="nrg-20201231.xsd#nrg_GladstonePowerStationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_b130119b-4529-4ea7-ac56-83da28ae669c" xlink:to="loc_nrg_GladstonePowerStationMember_3538beb7-c56f-4121-869b-2131b994d320" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_IvampahMasterHoldingsLLCMember_c62889d3-2309-4129-b7f9-a0103e0350e5" xlink:href="nrg-20201231.xsd#nrg_IvampahMasterHoldingsLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_b130119b-4529-4ea7-ac56-83da28ae669c" xlink:to="loc_nrg_IvampahMasterHoldingsLLCMember_c62889d3-2309-4129-b7f9-a0103e0350e5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_WatsonCogenerationCompanyMember_4a513daa-b360-4afd-b084-104b5bb524e3" xlink:href="nrg-20201231.xsd#nrg_WatsonCogenerationCompanyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_b130119b-4529-4ea7-ac56-83da28ae669c" xlink:to="loc_nrg_WatsonCogenerationCompanyMember_4a513daa-b360-4afd-b084-104b5bb524e3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_MidwaySunsetCogenerationCompanyMember_e3ed7f65-9130-41bf-bdc1-abd4dd221e12" xlink:href="nrg-20201231.xsd#nrg_MidwaySunsetCogenerationCompanyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_b130119b-4529-4ea7-ac56-83da28ae669c" xlink:to="loc_nrg_MidwaySunsetCogenerationCompanyMember_e3ed7f65-9130-41bf-bdc1-abd4dd221e12" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_PetraNovaParishHoldingsMember_4aefc8ca-e354-48f3-812e-d9ba8079a239" xlink:href="nrg-20201231.xsd#nrg_PetraNovaParishHoldingsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_b130119b-4529-4ea7-ac56-83da28ae669c" xlink:to="loc_nrg_PetraNovaParishHoldingsMember_4aefc8ca-e354-48f3-812e-d9ba8079a239" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/InvestmentsAccountedforbytheEquityMethodandVariableInterestEntitiesPGEBankruptcyDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#InvestmentsAccountedforbytheEquityMethodandVariableInterestEntitiesPGEBankruptcyDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/InvestmentsAccountedforbytheEquityMethodandVariableInterestEntitiesPGEBankruptcyDetails" xlink:type="extended" id="iad12e304aff84bdfba1635ff578dce6a_InvestmentsAccountedforbytheEquityMethodandVariableInterestEntitiesPGEBankruptcyDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_d352f2d4-99d5-4a2b-9231-b118c45d1896" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentDividendsOrDistributions_0dd4dcd2-534f-4a9a-b28f-3e0c6d697049" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityMethodInvestmentDividendsOrDistributions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_d352f2d4-99d5-4a2b-9231-b118c45d1896" xlink:to="loc_us-gaap_EquityMethodInvestmentDividendsOrDistributions_0dd4dcd2-534f-4a9a-b28f-3e0c6d697049" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_a6c1a222-25e4-46ad-8598-0790937720a8" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityMethodInvestmentOwnershipPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_d352f2d4-99d5-4a2b-9231-b118c45d1896" xlink:to="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_a6c1a222-25e4-46ad-8598-0790937720a8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_f2f3b0b1-8ad3-4935-89ab-67b5f3b34483" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_d352f2d4-99d5-4a2b-9231-b118c45d1896" xlink:to="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_f2f3b0b1-8ad3-4935-89ab-67b5f3b34483" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_7d0a8133-ed88-4408-b610-d8d53e35f101" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_f2f3b0b1-8ad3-4935-89ab-67b5f3b34483" xlink:to="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_7d0a8133-ed88-4408-b610-d8d53e35f101" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_7d0a8133-ed88-4408-b610-d8d53e35f101_default" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_7d0a8133-ed88-4408-b610-d8d53e35f101" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_7d0a8133-ed88-4408-b610-d8d53e35f101_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_98e4c4a1-5df6-41c5-92c6-734e6d4ae537" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_7d0a8133-ed88-4408-b610-d8d53e35f101" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_98e4c4a1-5df6-41c5-92c6-734e6d4ae537" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_AguaCalienteMember_27e1dee0-dfce-4876-8ab8-c3fe76e9a5fa" xlink:href="nrg-20201231.xsd#nrg_AguaCalienteMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_98e4c4a1-5df6-41c5-92c6-734e6d4ae537" xlink:to="loc_nrg_AguaCalienteMember_27e1dee0-dfce-4876-8ab8-c3fe76e9a5fa" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_IvampahMasterHoldingsLLCMember_f0f2fd1a-e566-40a8-95b4-47fecef73d88" xlink:href="nrg-20201231.xsd#nrg_IvampahMasterHoldingsLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_98e4c4a1-5df6-41c5-92c6-734e6d4ae537" xlink:to="loc_nrg_IvampahMasterHoldingsLLCMember_f0f2fd1a-e566-40a8-95b4-47fecef73d88" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/InvestmentsAccountedforbytheEquityMethodandVariableInterestEntitiesVariableInterestEntitiesDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#InvestmentsAccountedforbytheEquityMethodandVariableInterestEntitiesVariableInterestEntitiesDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/InvestmentsAccountedforbytheEquityMethodandVariableInterestEntitiesVariableInterestEntitiesDetails" xlink:type="extended" id="i64b7fda7a6c24db1a9b317250af0d13c_InvestmentsAccountedforbytheEquityMethodandVariableInterestEntitiesVariableInterestEntitiesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_e500b540-656c-40a6-b330-eede96656e84" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_60e82404-b03e-4f14-9b7f-59c147b74f73" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityMethodInvestmentOwnershipPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_e500b540-656c-40a6-b330-eede96656e84" xlink:to="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_60e82404-b03e-4f14-9b7f-59c147b74f73" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_NumberOfSolarElectricGeneratingProjects_a867593f-5b75-415e-b86f-f0593dfea8a4" xlink:href="nrg-20201231.xsd#nrg_NumberOfSolarElectricGeneratingProjects"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_e500b540-656c-40a6-b330-eede96656e84" xlink:to="loc_nrg_NumberOfSolarElectricGeneratingProjects_a867593f-5b75-415e-b86f-f0593dfea8a4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_PowerGenerationCapacityMegawatts_34a93d43-abe6-4960-b23b-bdba14448f83" xlink:href="nrg-20201231.xsd#nrg_PowerGenerationCapacityMegawatts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_e500b540-656c-40a6-b330-eede96656e84" xlink:to="loc_nrg_PowerGenerationCapacityMegawatts_34a93d43-abe6-4960-b23b-bdba14448f83" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInRestrictedCash_28deb2bb-49b7-49b5-ad29-409cc180d63c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncreaseDecreaseInRestrictedCash"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_e500b540-656c-40a6-b330-eede96656e84" xlink:to="loc_us-gaap_IncreaseDecreaseInRestrictedCash_28deb2bb-49b7-49b5-ad29-409cc180d63c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeconsolidationRevaluationOfRetainedInvestmentGainOrLossAmount_050d8ee8-e410-4b96-b85d-303845fc966b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeconsolidationRevaluationOfRetainedInvestmentGainOrLossAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_e500b540-656c-40a6-b330-eede96656e84" xlink:to="loc_us-gaap_DeconsolidationRevaluationOfRetainedInvestmentGainOrLossAmount_050d8ee8-e410-4b96-b85d-303845fc966b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInOperatingAssets_41ec0428-e0d7-4821-896e-0fd6c4d943f5" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncreaseDecreaseInOperatingAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_e500b540-656c-40a6-b330-eede96656e84" xlink:to="loc_us-gaap_IncreaseDecreaseInOperatingAssets_41ec0428-e0d7-4821-896e-0fd6c4d943f5" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInOperatingLiabilities_4fe14584-3cf2-41a0-9ba7-d717971d9e9d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncreaseDecreaseInOperatingLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_e500b540-656c-40a6-b330-eede96656e84" xlink:to="loc_us-gaap_IncreaseDecreaseInOperatingLiabilities_4fe14584-3cf2-41a0-9ba7-d717971d9e9d" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_d2285b4e-5818-4f5d-8a69-8ac8906060ad" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_e500b540-656c-40a6-b330-eede96656e84" xlink:to="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_d2285b4e-5818-4f5d-8a69-8ac8906060ad" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_0432cae0-a11a-43d0-a02e-d6b3dd4b2a63" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_d2285b4e-5818-4f5d-8a69-8ac8906060ad" xlink:to="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_0432cae0-a11a-43d0-a02e-d6b3dd4b2a63" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_0432cae0-a11a-43d0-a02e-d6b3dd4b2a63_default" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_0432cae0-a11a-43d0-a02e-d6b3dd4b2a63" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_0432cae0-a11a-43d0-a02e-d6b3dd4b2a63_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_117dabcc-fe91-42a1-9ad9-f2869a0820be" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_0432cae0-a11a-43d0-a02e-d6b3dd4b2a63" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_117dabcc-fe91-42a1-9ad9-f2869a0820be" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_IvampahMasterHoldingsLLCMember_9a2de39b-3dc3-4e81-a7b8-4a743e6c7a44" xlink:href="nrg-20201231.xsd#nrg_IvampahMasterHoldingsLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_117dabcc-fe91-42a1-9ad9-f2869a0820be" xlink:to="loc_nrg_IvampahMasterHoldingsLLCMember_9a2de39b-3dc3-4e81-a7b8-4a743e6c7a44" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_GladstonePowerStationMember_96f4f606-9c5e-441b-96d7-a96ccdad9c34" xlink:href="nrg-20201231.xsd#nrg_GladstonePowerStationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_117dabcc-fe91-42a1-9ad9-f2869a0820be" xlink:to="loc_nrg_GladstonePowerStationMember_96f4f606-9c5e-441b-96d7-a96ccdad9c34" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/InvestmentsAccountedforbytheEquityMethodandVariableInterestEntitiesOtherEquityInvestmentsDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#InvestmentsAccountedforbytheEquityMethodandVariableInterestEntitiesOtherEquityInvestmentsDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/InvestmentsAccountedforbytheEquityMethodandVariableInterestEntitiesOtherEquityInvestmentsDetails" xlink:type="extended" id="icdb3a0af6173410fbe72a5fed8f70df0_InvestmentsAccountedforbytheEquityMethodandVariableInterestEntitiesOtherEquityInvestmentsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_ec025c16-2dea-4cb9-8526-a9d0efcd0f2c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_126f57e2-12b7-42bf-a97e-9de42c695c50" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityMethodInvestmentOwnershipPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_ec025c16-2dea-4cb9-8526-a9d0efcd0f2c" xlink:to="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_126f57e2-12b7-42bf-a97e-9de42c695c50" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_PowerGenerationCapacityMegawatts_7a62ea74-6959-4c26-a691-fccbf0e4e3b5" xlink:href="nrg-20201231.xsd#nrg_PowerGenerationCapacityMegawatts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_ec025c16-2dea-4cb9-8526-a9d0efcd0f2c" xlink:to="loc_nrg_PowerGenerationCapacityMegawatts_7a62ea74-6959-4c26-a691-fccbf0e4e3b5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestments_d1e3fb44-2ba4-4a90-8353-0cd8a7c4cd67" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_ec025c16-2dea-4cb9-8526-a9d0efcd0f2c" xlink:to="loc_us-gaap_EquityMethodInvestments_d1e3fb44-2ba4-4a90-8353-0cd8a7c4cd67" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromDivestitureOfBusinesses_eff93e0e-05dc-471c-9d99-28976ac894b3" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ProceedsFromDivestitureOfBusinesses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_ec025c16-2dea-4cb9-8526-a9d0efcd0f2c" xlink:to="loc_us-gaap_ProceedsFromDivestitureOfBusinesses_eff93e0e-05dc-471c-9d99-28976ac894b3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_8c25d072-b950-4513-88e8-84758af7dc26" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_ec025c16-2dea-4cb9-8526-a9d0efcd0f2c" xlink:to="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_8c25d072-b950-4513-88e8-84758af7dc26" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_e36e56f8-2d46-4202-b8f1-e4eaab806434" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_8c25d072-b950-4513-88e8-84758af7dc26" xlink:to="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_e36e56f8-2d46-4202-b8f1-e4eaab806434" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_e36e56f8-2d46-4202-b8f1-e4eaab806434_default" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_e36e56f8-2d46-4202-b8f1-e4eaab806434" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_e36e56f8-2d46-4202-b8f1-e4eaab806434_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_8b568184-c7bf-4af9-9156-052952b07afd" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_e36e56f8-2d46-4202-b8f1-e4eaab806434" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_8b568184-c7bf-4af9-9156-052952b07afd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_GladstonePowerStationMember_6b13ab81-8280-435f-a6e2-b7c4aa9dae23" xlink:href="nrg-20201231.xsd#nrg_GladstonePowerStationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_8b568184-c7bf-4af9-9156-052952b07afd" xlink:to="loc_nrg_GladstonePowerStationMember_6b13ab81-8280-435f-a6e2-b7c4aa9dae23" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_HomeSolarMember_ff00b4c6-4c94-49a4-9b08-6ad8adaac8dc" xlink:href="nrg-20201231.xsd#nrg_HomeSolarMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_8b568184-c7bf-4af9-9156-052952b07afd" xlink:to="loc_nrg_HomeSolarMember_ff00b4c6-4c94-49a4-9b08-6ad8adaac8dc" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/InvestmentsAccountedforUsingtheEquityMethodandVariableInterestEntitiesorVIEsSummarizedFinancialInformationDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#InvestmentsAccountedforUsingtheEquityMethodandVariableInterestEntitiesorVIEsSummarizedFinancialInformationDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/InvestmentsAccountedforUsingtheEquityMethodandVariableInterestEntitiesorVIEsSummarizedFinancialInformationDetails" xlink:type="extended" id="idea73535ce62453b83a84acb3381c6ea_InvestmentsAccountedforUsingtheEquityMethodandVariableInterestEntitiesorVIEsSummarizedFinancialInformationDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_bfef81f5-d443-447a-bd96-b8a4e4975263" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableNetCurrent_5893cca2-1405-4f62-802a-e3c68b74b92b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccountsReceivableNetCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_bfef81f5-d443-447a-bd96-b8a4e4975263" xlink:to="loc_us-gaap_AccountsReceivableNetCurrent_5893cca2-1405-4f62-802a-e3c68b74b92b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsCurrent_9bbd8add-951f-482f-996e-e4cb8554ac30" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherAssetsCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_bfef81f5-d443-447a-bd96-b8a4e4975263" xlink:to="loc_us-gaap_OtherAssetsCurrent_9bbd8add-951f-482f-996e-e4cb8554ac30" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_ccb58d3a-548d-4831-b9b9-c17de1c77537" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PropertyPlantAndEquipmentNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_bfef81f5-d443-447a-bd96-b8a4e4975263" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_ccb58d3a-548d-4831-b9b9-c17de1c77537" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsNoncurrent_2c3d6f40-bd97-47a3-81dc-11976dfc71a4" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherAssetsNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_bfef81f5-d443-447a-bd96-b8a4e4975263" xlink:to="loc_us-gaap_OtherAssetsNoncurrent_2c3d6f40-bd97-47a3-81dc-11976dfc71a4" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_063ae96f-adb1-460e-b895-7906e6e37c20" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_Assets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_bfef81f5-d443-447a-bd96-b8a4e4975263" xlink:to="loc_us-gaap_Assets_063ae96f-adb1-460e-b895-7906e6e37c20" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesCurrent_07adf4cb-42df-4f04-91bc-2b34a22ee222" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_bfef81f5-d443-447a-bd96-b8a4e4975263" xlink:to="loc_us-gaap_LiabilitiesCurrent_07adf4cb-42df-4f04-91bc-2b34a22ee222" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_10e662e2-94aa-40a4-a9fe-01f179322260" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_bfef81f5-d443-447a-bd96-b8a4e4975263" xlink:to="loc_us-gaap_LongTermDebt_10e662e2-94aa-40a4-a9fe-01f179322260" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLiabilitiesNoncurrent_2a92587d-1455-4cc4-be3f-8cb20c70f5c0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherLiabilitiesNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_bfef81f5-d443-447a-bd96-b8a4e4975263" xlink:to="loc_us-gaap_OtherLiabilitiesNoncurrent_2a92587d-1455-4cc4-be3f-8cb20c70f5c0" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Liabilities_aa9f381c-b8ca-4cc3-a902-ad1b9659cf8d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_Liabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_bfef81f5-d443-447a-bd96-b8a4e4975263" xlink:to="loc_us-gaap_Liabilities_aa9f381c-b8ca-4cc3-a902-ad1b9659cf8d" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RedeemableNoncontrollingInterestEquityCarryingAmount_9b0f7b20-dfa3-4b67-9611-7864ffab8fc0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RedeemableNoncontrollingInterestEquityCarryingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_bfef81f5-d443-447a-bd96-b8a4e4975263" xlink:to="loc_us-gaap_RedeemableNoncontrollingInterestEquityCarryingAmount_9b0f7b20-dfa3-4b67-9611-7864ffab8fc0" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_NetAssetsLessNoncontrollingInterest_0e3da0dd-7691-4545-b490-5de21b31bc34" xlink:href="nrg-20201231.xsd#nrg_NetAssetsLessNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_bfef81f5-d443-447a-bd96-b8a4e4975263" xlink:to="loc_nrg_NetAssetsLessNoncontrollingInterest_0e3da0dd-7691-4545-b490-5de21b31bc34" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_f5789600-52c6-41be-8c48-64347e54d9e0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_bfef81f5-d443-447a-bd96-b8a4e4975263" xlink:to="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_f5789600-52c6-41be-8c48-64347e54d9e0" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_1d8a501c-7def-4df0-96bc-c38b4e60026e" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_f5789600-52c6-41be-8c48-64347e54d9e0" xlink:to="loc_srt_ConsolidatedEntitiesAxis_1d8a501c-7def-4df0-96bc-c38b4e60026e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_1d8a501c-7def-4df0-96bc-c38b4e60026e_default" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_1d8a501c-7def-4df0-96bc-c38b4e60026e" xlink:to="loc_srt_ConsolidatedEntitiesDomain_1d8a501c-7def-4df0-96bc-c38b4e60026e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_aee8af52-1b26-4c5b-85f4-3a76c64be039" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_1d8a501c-7def-4df0-96bc-c38b4e60026e" xlink:to="loc_srt_ConsolidatedEntitiesDomain_aee8af52-1b26-4c5b-85f4-3a76c64be039" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableInterestEntityPrimaryBeneficiaryMember_976ce91a-9f47-418a-b06f-1cd5709e5b0e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_VariableInterestEntityPrimaryBeneficiaryMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_aee8af52-1b26-4c5b-85f4-3a76c64be039" xlink:to="loc_us-gaap_VariableInterestEntityPrimaryBeneficiaryMember_976ce91a-9f47-418a-b06f-1cd5709e5b0e" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/EarningsPerShare" xlink:type="simple" xlink:href="nrg-20201231.xsd#EarningsPerShare"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/EarningsPerShare" xlink:type="extended" id="i9c7bf427cc7a45d9913a5b9f9894c1fe_EarningsPerShare"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/EarningsPerShareTables" xlink:type="simple" xlink:href="nrg-20201231.xsd#EarningsPerShareTables"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/EarningsPerShareTables" xlink:type="extended" id="i44a8dcd8344648678d317b255cec5d69_EarningsPerShareTables"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/EarningsPerShareDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#EarningsPerShareDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/EarningsPerShareDetails" xlink:type="extended" id="i5cd709e8733e4692aa908b7277fba65f_EarningsPerShareDetails"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/SegmentReporting" xlink:type="simple" xlink:href="nrg-20201231.xsd#SegmentReporting"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/SegmentReporting" xlink:type="extended" id="i6f284c5a613342d582912310fe7857af_SegmentReporting"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/SegmentReportingTables" xlink:type="simple" xlink:href="nrg-20201231.xsd#SegmentReportingTables"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/SegmentReportingTables" xlink:type="extended" id="ie95ad7ae08444449b8fc6774523c1053_SegmentReportingTables"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/SegmentReportingDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#SegmentReportingDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/SegmentReportingDetails" xlink:type="extended" id="i5bd99916652e451fabe24d29ff2bd281_SegmentReportingDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_cac75970-e7e5-4bc6-9acb-baa08ac559df" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskPercentage1_b05b440f-6e15-4494-a5a7-15b2fde5dcce" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ConcentrationRiskPercentage1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_cac75970-e7e5-4bc6-9acb-baa08ac559df" xlink:to="loc_us-gaap_ConcentrationRiskPercentage1_b05b440f-6e15-4494-a5a7-15b2fde5dcce" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementAbstract_16b1c621-24c2-4f67-9f56-3b75bf17192b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeStatementAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_cac75970-e7e5-4bc6-9acb-baa08ac559df" xlink:to="loc_us-gaap_IncomeStatementAbstract_16b1c621-24c2-4f67-9f56-3b75bf17192b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Revenues_40e363de-5681-4594-8441-c8519469a79e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_Revenues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementAbstract_16b1c621-24c2-4f67-9f56-3b75bf17192b" xlink:to="loc_us-gaap_Revenues_40e363de-5681-4594-8441-c8519469a79e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_Costofrevenueincludingsellingmarketingandgeneraladministrative_60377b11-a9fd-42c6-ab75-ec23aa7140c5" xlink:href="nrg-20201231.xsd#nrg_Costofrevenueincludingsellingmarketingandgeneraladministrative"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementAbstract_16b1c621-24c2-4f67-9f56-3b75bf17192b" xlink:to="loc_nrg_Costofrevenueincludingsellingmarketingandgeneraladministrative_60377b11-a9fd-42c6-ab75-ec23aa7140c5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepreciationDepletionAndAmortization_a9541f5c-ac0f-4a7b-97c2-07b1969a7357" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DepreciationDepletionAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementAbstract_16b1c621-24c2-4f67-9f56-3b75bf17192b" xlink:to="loc_us-gaap_DepreciationDepletionAndAmortization_a9541f5c-ac0f-4a7b-97c2-07b1969a7357" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetImpairmentCharges_2b17d23b-543b-4867-944f-a7f2495ea2bc" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AssetImpairmentCharges"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementAbstract_16b1c621-24c2-4f67-9f56-3b75bf17192b" xlink:to="loc_us-gaap_AssetImpairmentCharges_2b17d23b-543b-4867-944f-a7f2495ea2bc" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResearchAndDevelopmentExpense_c96d87b8-669e-4124-976d-9b7cc74cccbd" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ResearchAndDevelopmentExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementAbstract_16b1c621-24c2-4f67-9f56-3b75bf17192b" xlink:to="loc_us-gaap_ResearchAndDevelopmentExpense_c96d87b8-669e-4124-976d-9b7cc74cccbd" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostsAndExpenses_f6e59652-51a8-4022-aa42-73e51ccfc726" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CostsAndExpenses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementAbstract_16b1c621-24c2-4f67-9f56-3b75bf17192b" xlink:to="loc_us-gaap_CostsAndExpenses_f6e59652-51a8-4022-aa42-73e51ccfc726" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnSaleOfOtherAssets_40bbb299-26bf-4206-baa7-ec447fcc6b71" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GainLossOnSaleOfOtherAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementAbstract_16b1c621-24c2-4f67-9f56-3b75bf17192b" xlink:to="loc_us-gaap_GainLossOnSaleOfOtherAssets_40bbb299-26bf-4206-baa7-ec447fcc6b71" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingIncomeLoss_824764b6-2dd4-4156-8dc9-c947db98aa0a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementAbstract_16b1c621-24c2-4f67-9f56-3b75bf17192b" xlink:to="loc_us-gaap_OperatingIncomeLoss_824764b6-2dd4-4156-8dc9-c947db98aa0a" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromEquityMethodInvestments_3fb2707c-4686-4728-b41a-414950932a6d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeLossFromEquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementAbstract_16b1c621-24c2-4f67-9f56-3b75bf17192b" xlink:to="loc_us-gaap_IncomeLossFromEquityMethodInvestments_3fb2707c-4686-4728-b41a-414950932a6d" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ImpairmentOfInvestments_7dfb5650-51dc-4a1b-93f4-ad476ca6faa8" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ImpairmentOfInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementAbstract_16b1c621-24c2-4f67-9f56-3b75bf17192b" xlink:to="loc_us-gaap_ImpairmentOfInvestments_7dfb5650-51dc-4a1b-93f4-ad476ca6faa8" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNonoperatingIncomeExpense_542101a0-280b-43c3-b2f0-298f030623c1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherNonoperatingIncomeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementAbstract_16b1c621-24c2-4f67-9f56-3b75bf17192b" xlink:to="loc_us-gaap_OtherNonoperatingIncomeExpense_542101a0-280b-43c3-b2f0-298f030623c1" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainsLossesOnExtinguishmentOfDebt_7d6ec7c0-96a9-4d23-9eb1-649e0430fef9" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GainsLossesOnExtinguishmentOfDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementAbstract_16b1c621-24c2-4f67-9f56-3b75bf17192b" xlink:to="loc_us-gaap_GainsLossesOnExtinguishmentOfDebt_7d6ec7c0-96a9-4d23-9eb1-649e0430fef9" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpense_9486bd95-dd13-4a52-8480-d35bd09dd0c6" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InterestExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementAbstract_16b1c621-24c2-4f67-9f56-3b75bf17192b" xlink:to="loc_us-gaap_InterestExpense_9486bd95-dd13-4a52-8480-d35bd09dd0c6" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_6ec1f048-1b64-4997-98a9-a7fd7419340c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementAbstract_16b1c621-24c2-4f67-9f56-3b75bf17192b" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_6ec1f048-1b64-4997-98a9-a7fd7419340c" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_81bbdf67-afc6-4b92-b962-79b94db86ff8" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeTaxExpenseBenefit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementAbstract_16b1c621-24c2-4f67-9f56-3b75bf17192b" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_81bbdf67-afc6-4b92-b962-79b94db86ff8" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest_f4060eea-86d6-438b-ac83-863502046b50" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementAbstract_16b1c621-24c2-4f67-9f56-3b75bf17192b" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest_f4060eea-86d6-438b-ac83-863502046b50" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToReportingEntity_7c38e3ad-0024-48bf-80d1-31cc16d0b6f7" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToReportingEntity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementAbstract_16b1c621-24c2-4f67-9f56-3b75bf17192b" xlink:to="loc_us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToReportingEntity_7c38e3ad-0024-48bf-80d1-31cc16d0b6f7" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_22b9871d-fa8b-4544-b3dd-cbcde4e1ab40" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ProfitLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementAbstract_16b1c621-24c2-4f67-9f56-3b75bf17192b" xlink:to="loc_us-gaap_ProfitLoss_22b9871d-fa8b-4544-b3dd-cbcde4e1ab40" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLossAttributableToNoncontrollingInterest_01eea642-f2a0-4f89-8b96-ead4758d74df" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NetIncomeLossAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementAbstract_16b1c621-24c2-4f67-9f56-3b75bf17192b" xlink:to="loc_us-gaap_NetIncomeLossAttributableToNoncontrollingInterest_01eea642-f2a0-4f89-8b96-ead4758d74df" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_520b6494-c780-42b2-b3b1-14da697ec372" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementAbstract_16b1c621-24c2-4f67-9f56-3b75bf17192b" xlink:to="loc_us-gaap_NetIncomeLoss_520b6494-c780-42b2-b3b1-14da697ec372" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationAdditionalInformationAbstract_d103f500-6c00-4618-b1dc-4989e54f5078" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SegmentReportingInformationAdditionalInformationAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_cac75970-e7e5-4bc6-9acb-baa08ac559df" xlink:to="loc_us-gaap_SegmentReportingInformationAdditionalInformationAbstract_d103f500-6c00-4618-b1dc-4989e54f5078" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestments_c53d969c-41d9-41f6-b296-655d42bfa8bb" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationAdditionalInformationAbstract_d103f500-6c00-4618-b1dc-4989e54f5078" xlink:to="loc_us-gaap_EquityMethodInvestments_c53d969c-41d9-41f6-b296-655d42bfa8bb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_CapitalExpenditures_82ca32be-9bd3-489b-aa96-29770336e409" xlink:href="nrg-20201231.xsd#nrg_CapitalExpenditures"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationAdditionalInformationAbstract_d103f500-6c00-4618-b1dc-4989e54f5078" xlink:to="loc_nrg_CapitalExpenditures_82ca32be-9bd3-489b-aa96-29770336e409" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_2c2877c8-edfe-4e98-b3a1-d9e57a535950" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_Goodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationAdditionalInformationAbstract_d103f500-6c00-4618-b1dc-4989e54f5078" xlink:to="loc_us-gaap_Goodwill_2c2877c8-edfe-4e98-b3a1-d9e57a535950" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_9e75b7af-eead-4898-8422-eb2b2076b8d6" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_Assets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationAdditionalInformationAbstract_d103f500-6c00-4618-b1dc-4989e54f5078" xlink:to="loc_us-gaap_Assets_9e75b7af-eead-4898-8422-eb2b2076b8d6" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_db07f9dd-50ba-4867-b897-1eda80572ff9" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_cac75970-e7e5-4bc6-9acb-baa08ac559df" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_db07f9dd-50ba-4867-b897-1eda80572ff9" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByTypeAxis_ec371000-2939-41e0-a1e4-c40546ed48cb" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ConcentrationRiskByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_db07f9dd-50ba-4867-b897-1eda80572ff9" xlink:to="loc_us-gaap_ConcentrationRiskByTypeAxis_ec371000-2939-41e0-a1e4-c40546ed48cb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_ec371000-2939-41e0-a1e4-c40546ed48cb_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_ec371000-2939-41e0-a1e4-c40546ed48cb" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_ec371000-2939-41e0-a1e4-c40546ed48cb_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_67118413-2708-4457-a64c-1636f3e36412" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_ec371000-2939-41e0-a1e4-c40546ed48cb" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_67118413-2708-4457-a64c-1636f3e36412" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerConcentrationRiskMember_c7aab46f-3c42-4577-a4f4-ec97eb9faca4" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CustomerConcentrationRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_67118413-2708-4457-a64c-1636f3e36412" xlink:to="loc_us-gaap_CustomerConcentrationRiskMember_c7aab46f-3c42-4577-a4f4-ec97eb9faca4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_223254bf-d48e-420e-9a45-937186d25834" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_db07f9dd-50ba-4867-b897-1eda80572ff9" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_223254bf-d48e-420e-9a45-937186d25834" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_223254bf-d48e-420e-9a45-937186d25834_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_223254bf-d48e-420e-9a45-937186d25834" xlink:to="loc_us-gaap_SegmentDomain_223254bf-d48e-420e-9a45-937186d25834_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_23793deb-92d3-4e50-be87-8f84a1f0da8a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_223254bf-d48e-420e-9a45-937186d25834" xlink:to="loc_us-gaap_SegmentDomain_23793deb-92d3-4e50-be87-8f84a1f0da8a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_TexasSegmentMember_6a6f4baa-697c-4c33-adb8-40b8749288ae" xlink:href="nrg-20201231.xsd#nrg_TexasSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_23793deb-92d3-4e50-be87-8f84a1f0da8a" xlink:to="loc_nrg_TexasSegmentMember_6a6f4baa-697c-4c33-adb8-40b8749288ae" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_EastSegmentMember_774b5da9-bc0c-4464-97ef-beed4a5add8a" xlink:href="nrg-20201231.xsd#nrg_EastSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_23793deb-92d3-4e50-be87-8f84a1f0da8a" xlink:to="loc_nrg_EastSegmentMember_774b5da9-bc0c-4464-97ef-beed4a5add8a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_WestAndOtherSegmentMember_bc1034dc-a491-43e9-8b93-68de3ccf2e15" xlink:href="nrg-20201231.xsd#nrg_WestAndOtherSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_23793deb-92d3-4e50-be87-8f84a1f0da8a" xlink:to="loc_nrg_WestAndOtherSegmentMember_bc1034dc-a491-43e9-8b93-68de3ccf2e15" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateMember_95ec830f-07b1-4411-8342-92a80957de8b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CorporateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_23793deb-92d3-4e50-be87-8f84a1f0da8a" xlink:to="loc_us-gaap_CorporateMember_95ec830f-07b1-4411-8342-92a80957de8b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_3070ff8a-1b7f-4140-9fea-a4ea9587ef98" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_db07f9dd-50ba-4867-b897-1eda80572ff9" xlink:to="loc_srt_ConsolidationItemsAxis_3070ff8a-1b7f-4140-9fea-a4ea9587ef98" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_3070ff8a-1b7f-4140-9fea-a4ea9587ef98_default" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_3070ff8a-1b7f-4140-9fea-a4ea9587ef98" xlink:to="loc_srt_ConsolidationItemsDomain_3070ff8a-1b7f-4140-9fea-a4ea9587ef98_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_c4057501-31af-4254-9836-5c4c42d568eb" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_3070ff8a-1b7f-4140-9fea-a4ea9587ef98" xlink:to="loc_srt_ConsolidationItemsDomain_c4057501-31af-4254-9836-5c4c42d568eb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_29a5189f-f19d-468a-af60-9a0fa6abb12a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_c4057501-31af-4254-9836-5c4c42d568eb" xlink:to="loc_us-gaap_OperatingSegmentsMember_29a5189f-f19d-468a-af60-9a0fa6abb12a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateNonSegmentMember_84ac498f-230f-4e57-bff6-59165d20a2bd" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CorporateNonSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_c4057501-31af-4254-9836-5c4c42d568eb" xlink:to="loc_us-gaap_CorporateNonSegmentMember_84ac498f-230f-4e57-bff6-59165d20a2bd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IntersegmentEliminationMember_edb223da-b94f-45c3-9513-e4719d43976c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IntersegmentEliminationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_c4057501-31af-4254-9836-5c4c42d568eb" xlink:to="loc_us-gaap_IntersegmentEliminationMember_edb223da-b94f-45c3-9513-e4719d43976c" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/IncomeTaxes" xlink:type="simple" xlink:href="nrg-20201231.xsd#IncomeTaxes"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/IncomeTaxes" xlink:type="extended" id="i8867fdfc5c134737bce640829e50819e_IncomeTaxes"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/IncomeTaxesTables" xlink:type="simple" xlink:href="nrg-20201231.xsd#IncomeTaxesTables"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/IncomeTaxesTables" xlink:type="extended" id="if2663803144a49d08edbce12f6460ec7_IncomeTaxesTables"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/IncomeTaxesIncomeTaxProvisionDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#IncomeTaxesIncomeTaxProvisionDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/IncomeTaxesIncomeTaxProvisionDetails" xlink:type="extended" id="ie9bee0b2f6f141aa9a8842f9954582d6_IncomeTaxesIncomeTaxProvisionDetails"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/IncomeTaxesDeferredTaxAssetsandLiabilitiesDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#IncomeTaxesDeferredTaxAssetsandLiabilitiesDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/IncomeTaxesDeferredTaxAssetsandLiabilitiesDetails" xlink:type="extended" id="if3c3983ea9bf44379ad714ff15fd7e4f_IncomeTaxesDeferredTaxAssetsandLiabilitiesDetails"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/IncomeTaxesNarrativeforDeferredTaxAssetsandValuationAllowanceTaxesReceivableandPayableDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#IncomeTaxesNarrativeforDeferredTaxAssetsandValuationAllowanceTaxesReceivableandPayableDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/IncomeTaxesNarrativeforDeferredTaxAssetsandValuationAllowanceTaxesReceivableandPayableDetails" xlink:type="extended" id="id0d94f8d028f4468a20e0daaf2ad925c_IncomeTaxesNarrativeforDeferredTaxAssetsandValuationAllowanceTaxesReceivableandPayableDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxContingencyLineItems_b55d025f-fcac-4881-ba6f-7e025d4a8d55" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeTaxContingencyLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxReconciliationChangeInDeferredTaxAssetsValuationAllowance_896e5c3c-e53d-4ca6-9759-1192e4540d6e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeTaxReconciliationChangeInDeferredTaxAssetsValuationAllowance"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxContingencyLineItems_b55d025f-fcac-4881-ba6f-7e025d4a8d55" xlink:to="loc_us-gaap_IncomeTaxReconciliationChangeInDeferredTaxAssetsValuationAllowance_896e5c3c-e53d-4ca6-9759-1192e4540d6e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_NetOperatingLossCarryforwardsUtilized_de328529-0442-4583-a9a8-fc07ccdf4c34" xlink:href="nrg-20201231.xsd#nrg_NetOperatingLossCarryforwardsUtilized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxContingencyLineItems_b55d025f-fcac-4881-ba6f-7e025d4a8d55" xlink:to="loc_nrg_NetOperatingLossCarryforwardsUtilized_de328529-0442-4583-a9a8-fc07ccdf4c34" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredTaxAssetsLiabilitiesNet_6b5f1fb8-6663-4e2c-be9e-4777dac722e4" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredTaxAssetsLiabilitiesNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxContingencyLineItems_b55d025f-fcac-4881-ba6f-7e025d4a8d55" xlink:to="loc_us-gaap_DeferredTaxAssetsLiabilitiesNet_6b5f1fb8-6663-4e2c-be9e-4777dac722e4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_NetDeferredTaxAssetBeforeValuationAllowance_b726d64b-ba03-43d8-a3c8-d82b72a82e40" xlink:href="nrg-20201231.xsd#nrg_NetDeferredTaxAssetBeforeValuationAllowance"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxContingencyLineItems_b55d025f-fcac-4881-ba6f-7e025d4a8d55" xlink:to="loc_nrg_NetDeferredTaxAssetBeforeValuationAllowance_b726d64b-ba03-43d8-a3c8-d82b72a82e40" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLossCarryforwards_74cb69e0-194d-4a76-aa0d-276825033347" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLossCarryforwards"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxContingencyLineItems_b55d025f-fcac-4881-ba6f-7e025d4a8d55" xlink:to="loc_us-gaap_OperatingLossCarryforwards_74cb69e0-194d-4a76-aa0d-276825033347" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredTaxAssetsValuationAllowance_0175c46c-f6c7-45ed-94b3-f60167612c2d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredTaxAssetsValuationAllowance"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxContingencyLineItems_b55d025f-fcac-4881-ba6f-7e025d4a8d55" xlink:to="loc_us-gaap_DeferredTaxAssetsValuationAllowance_0175c46c-f6c7-45ed-94b3-f60167612c2d" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccruedIncomeTaxesCurrent_82ab20c2-2726-4971-99a7-ac487c688214" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccruedIncomeTaxesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxContingencyLineItems_b55d025f-fcac-4881-ba6f-7e025d4a8d55" xlink:to="loc_us-gaap_AccruedIncomeTaxesCurrent_82ab20c2-2726-4971-99a7-ac487c688214" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxReceivable_282a0cc4-9de2-4fc6-aad4-5c63e351889a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeTaxReceivable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxContingencyLineItems_b55d025f-fcac-4881-ba6f-7e025d4a8d55" xlink:to="loc_us-gaap_IncomeTaxReceivable_282a0cc4-9de2-4fc6-aad4-5c63e351889a" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxContingencyTable_733fcd93-f830-4a9e-a322-6999f44853c4" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeTaxContingencyTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_IncomeTaxContingencyLineItems_b55d025f-fcac-4881-ba6f-7e025d4a8d55" xlink:to="loc_us-gaap_IncomeTaxContingencyTable_733fcd93-f830-4a9e-a322-6999f44853c4" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxAuthorityAxis_c86000af-ecf1-4564-95a1-289bc1b1d193" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeTaxAuthorityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeTaxContingencyTable_733fcd93-f830-4a9e-a322-6999f44853c4" xlink:to="loc_us-gaap_IncomeTaxAuthorityAxis_c86000af-ecf1-4564-95a1-289bc1b1d193" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxAuthorityDomain_c86000af-ecf1-4564-95a1-289bc1b1d193_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeTaxAuthorityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeTaxAuthorityAxis_c86000af-ecf1-4564-95a1-289bc1b1d193" xlink:to="loc_us-gaap_IncomeTaxAuthorityDomain_c86000af-ecf1-4564-95a1-289bc1b1d193_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxAuthorityDomain_92415aeb-7e40-4f6d-96c7-fbb0681f55e5" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeTaxAuthorityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeTaxAuthorityAxis_c86000af-ecf1-4564-95a1-289bc1b1d193" xlink:to="loc_us-gaap_IncomeTaxAuthorityDomain_92415aeb-7e40-4f6d-96c7-fbb0681f55e5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DomesticCountryMember_2dff2625-5eb5-45a2-b238-13094993b81c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DomesticCountryMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxAuthorityDomain_92415aeb-7e40-4f6d-96c7-fbb0681f55e5" xlink:to="loc_us-gaap_DomesticCountryMember_2dff2625-5eb5-45a2-b238-13094993b81c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StateAndLocalJurisdictionMember_8af47b5e-603d-44dc-9639-fdf2f80385d6" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StateAndLocalJurisdictionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxAuthorityDomain_92415aeb-7e40-4f6d-96c7-fbb0681f55e5" xlink:to="loc_us-gaap_StateAndLocalJurisdictionMember_8af47b5e-603d-44dc-9639-fdf2f80385d6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignCountryMember_0f72c96f-cf37-4416-87e8-3e82af8bc474" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ForeignCountryMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxAuthorityDomain_92415aeb-7e40-4f6d-96c7-fbb0681f55e5" xlink:to="loc_us-gaap_ForeignCountryMember_0f72c96f-cf37-4416-87e8-3e82af8bc474" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/IncomeTaxesReconciliationofUncertainTaxBenefitsDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#IncomeTaxesReconciliationofUncertainTaxBenefitsDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/IncomeTaxesReconciliationofUncertainTaxBenefitsDetails" xlink:type="extended" id="ie989b7bc020d4d6da9398e7d7d9d247a_IncomeTaxesReconciliationofUncertainTaxBenefitsDetails"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/StockBasedCompensation" xlink:type="simple" xlink:href="nrg-20201231.xsd#StockBasedCompensation"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/StockBasedCompensation" xlink:type="extended" id="ia90333a88c78432ab5c371f101fd2f2b_StockBasedCompensation"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/StockBasedCompensationTables" xlink:type="simple" xlink:href="nrg-20201231.xsd#StockBasedCompensationTables"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/StockBasedCompensationTables" xlink:type="extended" id="i52dc665250a34e0eaba888e8ff6e18c7_StockBasedCompensationTables"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/StockBasedCompensationLongTermIncentivePlanDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#StockBasedCompensationLongTermIncentivePlanDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/StockBasedCompensationLongTermIncentivePlanDetails" xlink:type="extended" id="i2aab50c8c0024028a6baec460d258f51_StockBasedCompensationLongTermIncentivePlanDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_9ab7dda6-aa78-48d8-89f4-5366dc63e885" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNumberOfSharesPeriodIncreaseDecrease_02738838-8aa5-4a30-8432-32225ee7de3a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNumberOfSharesPeriodIncreaseDecrease"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_9ab7dda6-aa78-48d8-89f4-5366dc63e885" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNumberOfSharesPeriodIncreaseDecrease_02738838-8aa5-4a30-8432-32225ee7de3a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized_57c78ace-36cd-47d6-a9c1-4aa4c1e3e032" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_9ab7dda6-aa78-48d8-89f4-5366dc63e885" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized_57c78ace-36cd-47d6-a9c1-4aa4c1e3e032" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_c8df7c98-6575-4b80-adcf-1d927fd7906b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_9ab7dda6-aa78-48d8-89f4-5366dc63e885" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_c8df7c98-6575-4b80-adcf-1d927fd7906b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_faa3e4da-fc17-4160-8758-808d978d88c6" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_9ab7dda6-aa78-48d8-89f4-5366dc63e885" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_faa3e4da-fc17-4160-8758-808d978d88c6" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameAxis_b2e32d25-3068-49b2-bd3e-174495b7d226" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PlanNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_faa3e4da-fc17-4160-8758-808d978d88c6" xlink:to="loc_us-gaap_PlanNameAxis_b2e32d25-3068-49b2-bd3e-174495b7d226" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_b2e32d25-3068-49b2-bd3e-174495b7d226_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_b2e32d25-3068-49b2-bd3e-174495b7d226" xlink:to="loc_us-gaap_PlanNameDomain_b2e32d25-3068-49b2-bd3e-174495b7d226_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_9379721f-02bd-48e5-a72f-2f15f0e2e0fd" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_b2e32d25-3068-49b2-bd3e-174495b7d226" xlink:to="loc_us-gaap_PlanNameDomain_9379721f-02bd-48e5-a72f-2f15f0e2e0fd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_NRGLTIPMember_d0827252-32d4-468c-b7f7-f916e929c320" xlink:href="nrg-20201231.xsd#nrg_NRGLTIPMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_9379721f-02bd-48e5-a72f-2f15f0e2e0fd" xlink:to="loc_nrg_NRGLTIPMember_d0827252-32d4-468c-b7f7-f916e929c320" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_NRGGenOnLTIPMember_ae04d91d-eec4-46a0-b43b-a3a9261ae5a5" xlink:href="nrg-20201231.xsd#nrg_NRGGenOnLTIPMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_9379721f-02bd-48e5-a72f-2f15f0e2e0fd" xlink:to="loc_nrg_NRGGenOnLTIPMember_ae04d91d-eec4-46a0-b43b-a3a9261ae5a5" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/StockBasedCompensationRestrictedStockUnitsRSUsDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#StockBasedCompensationRestrictedStockUnitsRSUsDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/StockBasedCompensationRestrictedStockUnitsRSUsDetails" xlink:type="extended" id="i1e7bdd1eb4df4fbdb311cb4755c37b47_StockBasedCompensationRestrictedStockUnitsRSUsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_c4307076-e253-4cf3-9566-192eef842b8c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_06c3f706-173c-45e6-9e49-8e89ce032b36" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_c4307076-e253-4cf3-9566-192eef842b8c" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_06c3f706-173c-45e6-9e49-8e89ce032b36" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_fd74645a-a911-4365-ae7c-bfce920d46c1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_c4307076-e253-4cf3-9566-192eef842b8c" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_fd74645a-a911-4365-ae7c-bfce920d46c1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_fd0c3c1e-29de-412d-9a35-59620fe0e7ca" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_fd74645a-a911-4365-ae7c-bfce920d46c1" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_fd0c3c1e-29de-412d-9a35-59620fe0e7ca" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_0b8ed6c4-3889-4816-be35-c0fa9bda6eb0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_fd74645a-a911-4365-ae7c-bfce920d46c1" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_0b8ed6c4-3889-4816-be35-c0fa9bda6eb0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_93815778-9d0e-415e-bcbe-7c7b6710b746" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_fd74645a-a911-4365-ae7c-bfce920d46c1" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_93815778-9d0e-415e-bcbe-7c7b6710b746" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_ed3d4aa9-cacc-409b-8c6e-2d37e25b48dc" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_fd74645a-a911-4365-ae7c-bfce920d46c1" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_ed3d4aa9-cacc-409b-8c6e-2d37e25b48dc" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_aa0b4bee-9696-4899-b1fd-4962a4b4ee63" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_7330036d-0553-491f-be6f-9314b5e445c4" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_c4307076-e253-4cf3-9566-192eef842b8c" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_7330036d-0553-491f-be6f-9314b5e445c4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_8df19a62-95a3-4117-837a-3f80263379ac" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_7330036d-0553-491f-be6f-9314b5e445c4" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_8df19a62-95a3-4117-837a-3f80263379ac" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_2163ed9a-bc72-470e-9f48-386896e994fe" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_7330036d-0553-491f-be6f-9314b5e445c4" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_2163ed9a-bc72-470e-9f48-386896e994fe" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_607c4071-9c1b-4091-a0f6-a75e1940bba2" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_7330036d-0553-491f-be6f-9314b5e445c4" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_607c4071-9c1b-4091-a0f6-a75e1940bba2" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_b5125d51-c0e1-4614-a1a3-e6ea6d1be9d9" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_7330036d-0553-491f-be6f-9314b5e445c4" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_b5125d51-c0e1-4614-a1a3-e6ea6d1be9d9" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_eb5bacd9-3a80-4a2f-944d-be797c2d849d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue_0ff7cb31-5604-4ccf-a34d-e5a197f8fd30" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_c4307076-e253-4cf3-9566-192eef842b8c" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue_0ff7cb31-5604-4ccf-a34d-e5a197f8fd30" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_81c21f51-5d31-4150-b553-d096ffd0b9ac" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_341f91e2-31a1-40f1-8ad0-adb7f65c534d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_c4307076-e253-4cf3-9566-192eef842b8c" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_341f91e2-31a1-40f1-8ad0-adb7f65c534d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_88a7a3bc-cfe4-4591-8465-940c1f74c10b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_341f91e2-31a1-40f1-8ad0-adb7f65c534d" xlink:to="loc_us-gaap_AwardTypeAxis_88a7a3bc-cfe4-4591-8465-940c1f74c10b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_88a7a3bc-cfe4-4591-8465-940c1f74c10b_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_88a7a3bc-cfe4-4591-8465-940c1f74c10b" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_88a7a3bc-cfe4-4591-8465-940c1f74c10b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_35766e21-acc5-403b-b769-5917380e5873" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_88a7a3bc-cfe4-4591-8465-940c1f74c10b" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_35766e21-acc5-403b-b769-5917380e5873" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_4c0a86c6-e2c0-4a4f-907b-2948719b3870" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_35766e21-acc5-403b-b769-5917380e5873" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_4c0a86c6-e2c0-4a4f-907b-2948719b3870" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/StockBasedCompensationDeferredStockUnitsDSUsDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#StockBasedCompensationDeferredStockUnitsDSUsDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/StockBasedCompensationDeferredStockUnitsDSUsDetails" xlink:type="extended" id="i0de58c98cfee4f68800771d9d504625c_StockBasedCompensationDeferredStockUnitsDSUsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_f17b4605-eefa-4f59-9cf1-437fdd750598" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedNumberRollForward_985141bc-7206-4e1b-a46c-d1b9385b6fa1" xlink:href="nrg-20201231.xsd#nrg_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedNumberRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_f17b4605-eefa-4f59-9cf1-437fdd750598" xlink:to="loc_nrg_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedNumberRollForward_985141bc-7206-4e1b-a46c-d1b9385b6fa1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedNumber_a49fd59d-78b8-4359-9b0b-5a29395c82a4" xlink:href="nrg-20201231.xsd#nrg_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedNumberRollForward_985141bc-7206-4e1b-a46c-d1b9385b6fa1" xlink:to="loc_nrg_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedNumber_a49fd59d-78b8-4359-9b0b-5a29395c82a4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_bd7e1307-d01a-42ff-b34f-fa19057f066d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedNumberRollForward_985141bc-7206-4e1b-a46c-d1b9385b6fa1" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_bd7e1307-d01a-42ff-b34f-fa19057f066d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_13c6e288-dfae-4c5e-ae9d-0022f98bd1f7" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedNumberRollForward_985141bc-7206-4e1b-a46c-d1b9385b6fa1" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_13c6e288-dfae-4c5e-ae9d-0022f98bd1f7" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedNumber_e9506d5a-3282-456a-b2f3-f4bdfd083369" xlink:href="nrg-20201231.xsd#nrg_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedNumber"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_SharebasedCompensationArrangementbySharebasedPaymentAwardEquityInstrumentsOtherthanOptionsVestedWeightedAverageGrantDateFairValueAbstract_8c009e25-e3e5-4a3d-a54a-c1f77e242565" xlink:href="nrg-20201231.xsd#nrg_SharebasedCompensationArrangementbySharebasedPaymentAwardEquityInstrumentsOtherthanOptionsVestedWeightedAverageGrantDateFairValueAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_f17b4605-eefa-4f59-9cf1-437fdd750598" xlink:to="loc_nrg_SharebasedCompensationArrangementbySharebasedPaymentAwardEquityInstrumentsOtherthanOptionsVestedWeightedAverageGrantDateFairValueAbstract_8c009e25-e3e5-4a3d-a54a-c1f77e242565" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedWeightedAverageGrantDateFairValue_13d1dd08-56fc-43d3-97aa-e8ff541849d6" xlink:href="nrg-20201231.xsd#nrg_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_SharebasedCompensationArrangementbySharebasedPaymentAwardEquityInstrumentsOtherthanOptionsVestedWeightedAverageGrantDateFairValueAbstract_8c009e25-e3e5-4a3d-a54a-c1f77e242565" xlink:to="loc_nrg_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedWeightedAverageGrantDateFairValue_13d1dd08-56fc-43d3-97aa-e8ff541849d6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_5fd96b67-ad12-455b-a19e-9a6c31b5c017" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_SharebasedCompensationArrangementbySharebasedPaymentAwardEquityInstrumentsOtherthanOptionsVestedWeightedAverageGrantDateFairValueAbstract_8c009e25-e3e5-4a3d-a54a-c1f77e242565" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_5fd96b67-ad12-455b-a19e-9a6c31b5c017" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_fbe4023d-8593-40e7-a14b-d5f9fd491092" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_SharebasedCompensationArrangementbySharebasedPaymentAwardEquityInstrumentsOtherthanOptionsVestedWeightedAverageGrantDateFairValueAbstract_8c009e25-e3e5-4a3d-a54a-c1f77e242565" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_fbe4023d-8593-40e7-a14b-d5f9fd491092" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedWeightedAverageGrantDateFairValue_445e49f9-ace3-4ae2-b836-bd00c65d1f0d" xlink:href="nrg-20201231.xsd#nrg_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedWeightedAverageGrantDateFairValue"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedAggregateIntrinsicValue_6e28843f-26d0-4109-83b8-0324dedf4557" xlink:href="nrg-20201231.xsd#nrg_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedAggregateIntrinsicValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_f17b4605-eefa-4f59-9cf1-437fdd750598" xlink:to="loc_nrg_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedAggregateIntrinsicValue_6e28843f-26d0-4109-83b8-0324dedf4557" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsConversionsAggregateIntrinsicValue_eed93ef3-7b49-490d-985e-4964d7578027" xlink:href="nrg-20201231.xsd#nrg_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsConversionsAggregateIntrinsicValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_f17b4605-eefa-4f59-9cf1-437fdd750598" xlink:to="loc_nrg_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsConversionsAggregateIntrinsicValue_eed93ef3-7b49-490d-985e-4964d7578027" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_38dfe983-4814-4ec8-8b91-2b846e0404ac" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_c0e7b4f0-122e-4272-a243-e9ec65759c19" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_f17b4605-eefa-4f59-9cf1-437fdd750598" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_c0e7b4f0-122e-4272-a243-e9ec65759c19" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_8ba5d287-c185-4e13-90b4-5058ca8a916c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_c0e7b4f0-122e-4272-a243-e9ec65759c19" xlink:to="loc_us-gaap_AwardTypeAxis_8ba5d287-c185-4e13-90b4-5058ca8a916c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_8ba5d287-c185-4e13-90b4-5058ca8a916c_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_8ba5d287-c185-4e13-90b4-5058ca8a916c" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_8ba5d287-c185-4e13-90b4-5058ca8a916c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_305888e5-bb92-46cc-8563-a94fcb69d248" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_8ba5d287-c185-4e13-90b4-5058ca8a916c" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_305888e5-bb92-46cc-8563-a94fcb69d248" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_DeferredStockUnitsMember_33eb7446-8c3d-46bb-8e5f-dd0b84fb94b6" xlink:href="nrg-20201231.xsd#nrg_DeferredStockUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_305888e5-bb92-46cc-8563-a94fcb69d248" xlink:to="loc_nrg_DeferredStockUnitsMember_33eb7446-8c3d-46bb-8e5f-dd0b84fb94b6" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/StockBasedCompensationPerformanceStockUnitsRPSUsandMSUsPlandescriptionDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#StockBasedCompensationPerformanceStockUnitsRPSUsandMSUsPlandescriptionDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/StockBasedCompensationPerformanceStockUnitsRPSUsandMSUsPlandescriptionDetails" xlink:type="extended" id="i1b982cd3a948406caab4fdb4c6615630_StockBasedCompensationPerformanceStockUnitsRPSUsandMSUsPlandescriptionDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_bc8e2512-9b05-4955-8140-74ccc664496a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_f33d4999-750e-4f0b-a34f-7092a57d3a75" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_bc8e2512-9b05-4955-8140-74ccc664496a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_f33d4999-750e-4f0b-a34f-7092a57d3a75" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage_c2926356-1f9b-423b-b447-e14d6deb83c3" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_bc8e2512-9b05-4955-8140-74ccc664496a" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage_c2926356-1f9b-423b-b447-e14d6deb83c3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_f2c61bc9-00e1-4819-8669-1cdff93ec459" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_bc8e2512-9b05-4955-8140-74ccc664496a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_f2c61bc9-00e1-4819-8669-1cdff93ec459" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_22cdb908-2386-4d2d-b89f-20b8f1e822a5" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_bc8e2512-9b05-4955-8140-74ccc664496a" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_22cdb908-2386-4d2d-b89f-20b8f1e822a5" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_d71f2f5c-6a90-478a-88d2-9e86460760e4" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_22cdb908-2386-4d2d-b89f-20b8f1e822a5" xlink:to="loc_us-gaap_AwardTypeAxis_d71f2f5c-6a90-478a-88d2-9e86460760e4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_d71f2f5c-6a90-478a-88d2-9e86460760e4_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_d71f2f5c-6a90-478a-88d2-9e86460760e4" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_d71f2f5c-6a90-478a-88d2-9e86460760e4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_982b9578-b40a-46c4-80bf-b2a7a748e04b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_d71f2f5c-6a90-478a-88d2-9e86460760e4" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_982b9578-b40a-46c4-80bf-b2a7a748e04b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_RelativePerformanceStockUnitsMember_e7c9cfc3-e611-4f61-a601-c77faa30e716" xlink:href="nrg-20201231.xsd#nrg_RelativePerformanceStockUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_982b9578-b40a-46c4-80bf-b2a7a748e04b" xlink:to="loc_nrg_RelativePerformanceStockUnitsMember_e7c9cfc3-e611-4f61-a601-c77faa30e716" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_MarketStockUnitMember_c57c69b6-209c-40ca-b6a3-55a5e83e8fb9" xlink:href="nrg-20201231.xsd#nrg_MarketStockUnitMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_982b9578-b40a-46c4-80bf-b2a7a748e04b" xlink:to="loc_nrg_MarketStockUnitMember_c57c69b6-209c-40ca-b6a3-55a5e83e8fb9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VestingAxis_1facd058-805f-42f5-bfbf-9bb2790aebef" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_VestingAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_22cdb908-2386-4d2d-b89f-20b8f1e822a5" xlink:to="loc_us-gaap_VestingAxis_1facd058-805f-42f5-bfbf-9bb2790aebef" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VestingDomain_1facd058-805f-42f5-bfbf-9bb2790aebef_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_VestingDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_VestingAxis_1facd058-805f-42f5-bfbf-9bb2790aebef" xlink:to="loc_us-gaap_VestingDomain_1facd058-805f-42f5-bfbf-9bb2790aebef_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VestingDomain_2bbfa43f-b296-4e57-8c2e-c8e7848dc9da" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_VestingDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_VestingAxis_1facd058-805f-42f5-bfbf-9bb2790aebef" xlink:to="loc_us-gaap_VestingDomain_2bbfa43f-b296-4e57-8c2e-c8e7848dc9da" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationAwardTrancheOneMember_8963bdba-c337-4e8d-931b-4c8d680afa05" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationAwardTrancheOneMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VestingDomain_2bbfa43f-b296-4e57-8c2e-c8e7848dc9da" xlink:to="loc_us-gaap_ShareBasedCompensationAwardTrancheOneMember_8963bdba-c337-4e8d-931b-4c8d680afa05" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationAwardTrancheTwoMember_ae95e9b3-b109-4804-956b-9187d97720d0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationAwardTrancheTwoMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VestingDomain_2bbfa43f-b296-4e57-8c2e-c8e7848dc9da" xlink:to="loc_us-gaap_ShareBasedCompensationAwardTrancheTwoMember_ae95e9b3-b109-4804-956b-9187d97720d0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationAwardTrancheThreeMember_4289a278-87a8-41f4-aeca-83ebfcf0fb5a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationAwardTrancheThreeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VestingDomain_2bbfa43f-b296-4e57-8c2e-c8e7848dc9da" xlink:to="loc_us-gaap_ShareBasedCompensationAwardTrancheThreeMember_4289a278-87a8-41f4-aeca-83ebfcf0fb5a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_ShareBasedPaymentArrangementTrancheFourMember_44bd7f72-13f8-4817-ba91-43332badeb80" xlink:href="nrg-20201231.xsd#nrg_ShareBasedPaymentArrangementTrancheFourMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VestingDomain_2bbfa43f-b296-4e57-8c2e-c8e7848dc9da" xlink:to="loc_nrg_ShareBasedPaymentArrangementTrancheFourMember_44bd7f72-13f8-4817-ba91-43332badeb80" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_ShareBasedPaymentArrangementTrancheFiveMember_2cbcc18d-9046-404e-841a-46902e98c4f8" xlink:href="nrg-20201231.xsd#nrg_ShareBasedPaymentArrangementTrancheFiveMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VestingDomain_2bbfa43f-b296-4e57-8c2e-c8e7848dc9da" xlink:to="loc_nrg_ShareBasedPaymentArrangementTrancheFiveMember_2cbcc18d-9046-404e-841a-46902e98c4f8" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/StockBasedCompensationPerformanceStockUnitsDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#StockBasedCompensationPerformanceStockUnitsDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/StockBasedCompensationPerformanceStockUnitsDetails" xlink:type="extended" id="ic1a36ceeb076411c82b1c214acbd5c7e_StockBasedCompensationPerformanceStockUnitsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_e2a26ca1-6db1-4c38-a6b9-f0e754b319ee" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_220a5bfd-33cd-4604-ad7e-c337c815578c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_e2a26ca1-6db1-4c38-a6b9-f0e754b319ee" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_220a5bfd-33cd-4604-ad7e-c337c815578c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_dd5ffa8b-40d4-4649-a2e6-620492a9b5ac" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_220a5bfd-33cd-4604-ad7e-c337c815578c" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_dd5ffa8b-40d4-4649-a2e6-620492a9b5ac" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_9db4e810-47fb-4332-9895-a2e59b5563a5" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_220a5bfd-33cd-4604-ad7e-c337c815578c" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_9db4e810-47fb-4332-9895-a2e59b5563a5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_32705e7b-9b5c-461b-8188-11fe905a490d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_220a5bfd-33cd-4604-ad7e-c337c815578c" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_32705e7b-9b5c-461b-8188-11fe905a490d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_703c15ed-84a2-49ff-a42f-44d27e2bf52d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_220a5bfd-33cd-4604-ad7e-c337c815578c" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_703c15ed-84a2-49ff-a42f-44d27e2bf52d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_787b2054-4ab9-4b3d-abd8-a730e9ee215f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_03081522-22da-4a7b-9bcc-cfa32fc33728" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_e2a26ca1-6db1-4c38-a6b9-f0e754b319ee" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_03081522-22da-4a7b-9bcc-cfa32fc33728" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_d36749a2-2d25-4ba8-b691-28a221a0f312" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_03081522-22da-4a7b-9bcc-cfa32fc33728" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_d36749a2-2d25-4ba8-b691-28a221a0f312" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_8cf3f587-53ea-4e6e-bb15-284169082209" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_03081522-22da-4a7b-9bcc-cfa32fc33728" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_8cf3f587-53ea-4e6e-bb15-284169082209" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_45a7a5bb-3dc2-4e02-ada0-ef2140733f6d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_03081522-22da-4a7b-9bcc-cfa32fc33728" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_45a7a5bb-3dc2-4e02-ada0-ef2140733f6d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_6e7d1d1a-b9de-4811-8e3b-ab9894da2c02" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_03081522-22da-4a7b-9bcc-cfa32fc33728" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_6e7d1d1a-b9de-4811-8e3b-ab9894da2c02" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_8cc433ca-abf1-427e-ab7c-361ff0bb9e7b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage_66b5fd14-c8de-4c85-94fd-8ffcbba79106" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_03081522-22da-4a7b-9bcc-cfa32fc33728" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage_66b5fd14-c8de-4c85-94fd-8ffcbba79106" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract_719117f2-aa46-4614-9ad9-2df855e773f1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_e2a26ca1-6db1-4c38-a6b9-f0e754b319ee" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract_719117f2-aa46-4614-9ad9-2df855e773f1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate_88c3763b-2dae-4c28-b285-9ab9280ca32d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract_719117f2-aa46-4614-9ad9-2df855e773f1" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate_88c3763b-2dae-4c28-b285-9ab9280ca32d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1_397c4c1e-00d9-4153-b486-9e849bb69156" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract_719117f2-aa46-4614-9ad9-2df855e773f1" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1_397c4c1e-00d9-4153-b486-9e849bb69156" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate_a12f9d2f-4099-4bb2-904e-73f7d16936d2" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract_719117f2-aa46-4614-9ad9-2df855e773f1" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate_a12f9d2f-4099-4bb2-904e-73f7d16936d2" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_87ce4e31-4716-43ef-aad2-b51fd9f9bd92" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_e2a26ca1-6db1-4c38-a6b9-f0e754b319ee" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_87ce4e31-4716-43ef-aad2-b51fd9f9bd92" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_de2d81e0-cf33-4a6b-b89a-011fd73c13a0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_87ce4e31-4716-43ef-aad2-b51fd9f9bd92" xlink:to="loc_us-gaap_AwardTypeAxis_de2d81e0-cf33-4a6b-b89a-011fd73c13a0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_de2d81e0-cf33-4a6b-b89a-011fd73c13a0_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_de2d81e0-cf33-4a6b-b89a-011fd73c13a0" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_de2d81e0-cf33-4a6b-b89a-011fd73c13a0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_af68fddb-b722-49b0-8152-fadad0baa9fe" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_de2d81e0-cf33-4a6b-b89a-011fd73c13a0" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_af68fddb-b722-49b0-8152-fadad0baa9fe" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_PerformanceStockUnitsMember_086b0610-90d6-42fc-bfe8-496ef1359a1e" xlink:href="nrg-20201231.xsd#nrg_PerformanceStockUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_af68fddb-b722-49b0-8152-fadad0baa9fe" xlink:to="loc_nrg_PerformanceStockUnitsMember_086b0610-90d6-42fc-bfe8-496ef1359a1e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_RelativePerformanceStockUnitsMember_7efe46ef-988f-41d4-9a28-b3ade668beb2" xlink:href="nrg-20201231.xsd#nrg_RelativePerformanceStockUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_af68fddb-b722-49b0-8152-fadad0baa9fe" xlink:to="loc_nrg_RelativePerformanceStockUnitsMember_7efe46ef-988f-41d4-9a28-b3ade668beb2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_MarketStockUnitMember_e2f62447-fb7e-4d8b-b003-908dd8a259ff" xlink:href="nrg-20201231.xsd#nrg_MarketStockUnitMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_af68fddb-b722-49b0-8152-fadad0baa9fe" xlink:to="loc_nrg_MarketStockUnitMember_e2f62447-fb7e-4d8b-b003-908dd8a259ff" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardDateAxis_ebb3eba8-d645-4778-9688-bfdd635083da" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AwardDateAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_87ce4e31-4716-43ef-aad2-b51fd9f9bd92" xlink:to="loc_us-gaap_AwardDateAxis_ebb3eba8-d645-4778-9688-bfdd635083da" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardDateDomain_ebb3eba8-d645-4778-9688-bfdd635083da_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AwardDateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardDateAxis_ebb3eba8-d645-4778-9688-bfdd635083da" xlink:to="loc_us-gaap_AwardDateDomain_ebb3eba8-d645-4778-9688-bfdd635083da_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardDateDomain_afdb9d02-8155-42b2-aaa3-78233b87a6d7" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AwardDateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardDateAxis_ebb3eba8-d645-4778-9688-bfdd635083da" xlink:to="loc_us-gaap_AwardDateDomain_afdb9d02-8155-42b2-aaa3-78233b87a6d7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_GrantedIn2017Member_13ebf23c-ab86-4a69-9322-ceca5b57ed29" xlink:href="nrg-20201231.xsd#nrg_GrantedIn2017Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AwardDateDomain_afdb9d02-8155-42b2-aaa3-78233b87a6d7" xlink:to="loc_nrg_GrantedIn2017Member_13ebf23c-ab86-4a69-9322-ceca5b57ed29" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/StockBasedCompensationNonQualifiedStockOptionsDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#StockBasedCompensationNonQualifiedStockOptionsDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/StockBasedCompensationNonQualifiedStockOptionsDetails" xlink:type="extended" id="icc5e909fe815472a973796334617cc6f_StockBasedCompensationNonQualifiedStockOptionsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_5462a555-47af-4c24-be25-851e1bca6f1e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_b82f42f5-2303-4395-8fe1-075ebc0b3f17" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_5462a555-47af-4c24-be25-851e1bca6f1e" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_b82f42f5-2303-4395-8fe1-075ebc0b3f17" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_SharebasedCompensationArrangementbySharebasedPaymentAwardMaximumContractualTerm_ed47fbf1-c823-4376-932c-a9e46076d315" xlink:href="nrg-20201231.xsd#nrg_SharebasedCompensationArrangementbySharebasedPaymentAwardMaximumContractualTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_5462a555-47af-4c24-be25-851e1bca6f1e" xlink:to="loc_nrg_SharebasedCompensationArrangementbySharebasedPaymentAwardMaximumContractualTerm_ed47fbf1-c823-4376-932c-a9e46076d315" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_780edcdf-943e-4eeb-9c3d-fa6ebc9ec551" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_5462a555-47af-4c24-be25-851e1bca6f1e" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_780edcdf-943e-4eeb-9c3d-fa6ebc9ec551" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_717ddae5-c40e-4c9d-9bba-f76b51df73ad" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_780edcdf-943e-4eeb-9c3d-fa6ebc9ec551" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_717ddae5-c40e-4c9d-9bba-f76b51df73ad" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod_2bbead20-dd5c-4b2d-bd8c-fa29d1871217" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_780edcdf-943e-4eeb-9c3d-fa6ebc9ec551" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod_2bbead20-dd5c-4b2d-bd8c-fa29d1871217" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_f1fa5c0f-b683-4285-be8e-0e4aeff7c664" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_780edcdf-943e-4eeb-9c3d-fa6ebc9ec551" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_f1fa5c0f-b683-4285-be8e-0e4aeff7c664" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_0d07d0ab-af17-486b-9d3c-b59c5c69f3c1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber_2f9fb4ec-f8bf-497c-b097-613f0f49b335" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_780edcdf-943e-4eeb-9c3d-fa6ebc9ec551" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber_2f9fb4ec-f8bf-497c-b097-613f0f49b335" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward_95c4806c-99da-4dba-b145-dae489ce3b7b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_5462a555-47af-4c24-be25-851e1bca6f1e" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward_95c4806c-99da-4dba-b145-dae489ce3b7b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice_9ebcccfb-66bd-4380-a08d-fe974a4eeaed" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward_95c4806c-99da-4dba-b145-dae489ce3b7b" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice_9ebcccfb-66bd-4380-a08d-fe974a4eeaed" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice_9a5d7b2c-dd95-4968-adcb-6424f5092357" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward_95c4806c-99da-4dba-b145-dae489ce3b7b" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice_9a5d7b2c-dd95-4968-adcb-6424f5092357" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice_0f470701-cdad-402d-b732-65a3a51a179b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward_95c4806c-99da-4dba-b145-dae489ce3b7b" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice_0f470701-cdad-402d-b732-65a3a51a179b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice_7ca72618-6aaa-4c70-adca-77b1e1f35511" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice_64901f50-fcc8-4455-9472-ccbac85c5c0a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward_95c4806c-99da-4dba-b145-dae489ce3b7b" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice_64901f50-fcc8-4455-9472-ccbac85c5c0a" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAdditionalDisclosuresAbstract_0c2eb01d-9cfb-46e1-b0a9-51af6f6e300b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAdditionalDisclosuresAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_5462a555-47af-4c24-be25-851e1bca6f1e" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAdditionalDisclosuresAbstract_0c2eb01d-9cfb-46e1-b0a9-51af6f6e300b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2_2fa544e8-a775-446a-9f0f-17c780bf0937" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAdditionalDisclosuresAbstract_0c2eb01d-9cfb-46e1-b0a9-51af6f6e300b" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2_2fa544e8-a775-446a-9f0f-17c780bf0937" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1_8066058f-a6a2-4463-9caf-b4be260ca1ef" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAdditionalDisclosuresAbstract_0c2eb01d-9cfb-46e1-b0a9-51af6f6e300b" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1_8066058f-a6a2-4463-9caf-b4be260ca1ef" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue_d8063ce9-1dba-4a33-b11c-46f7e9676b75" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAdditionalDisclosuresAbstract_0c2eb01d-9cfb-46e1-b0a9-51af6f6e300b" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue_d8063ce9-1dba-4a33-b11c-46f7e9676b75" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1_c09fa901-d414-47a4-b62e-4d56a6989274" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAdditionalDisclosuresAbstract_0c2eb01d-9cfb-46e1-b0a9-51af6f6e300b" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1_c09fa901-d414-47a4-b62e-4d56a6989274" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_be4d489d-10d0-42ce-9bd2-80dee45f98aa" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_5462a555-47af-4c24-be25-851e1bca6f1e" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_be4d489d-10d0-42ce-9bd2-80dee45f98aa" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_dbfe6f9b-69f7-4510-9249-8bb7e71a8d14" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_be4d489d-10d0-42ce-9bd2-80dee45f98aa" xlink:to="loc_us-gaap_AwardTypeAxis_dbfe6f9b-69f7-4510-9249-8bb7e71a8d14" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_dbfe6f9b-69f7-4510-9249-8bb7e71a8d14_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_dbfe6f9b-69f7-4510-9249-8bb7e71a8d14" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_dbfe6f9b-69f7-4510-9249-8bb7e71a8d14_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_b592725b-8425-4646-b60f-aaf5cca2009e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_dbfe6f9b-69f7-4510-9249-8bb7e71a8d14" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_b592725b-8425-4646-b60f-aaf5cca2009e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_NonQualifiedStockOptionsMember_87269358-7bb5-449d-883d-4e1b4e9b8c18" xlink:href="nrg-20201231.xsd#nrg_NonQualifiedStockOptionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_b592725b-8425-4646-b60f-aaf5cca2009e" xlink:to="loc_nrg_NonQualifiedStockOptionsMember_87269358-7bb5-449d-883d-4e1b4e9b8c18" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/StockBasedCompensationIntrinsicValueofOptionsExercisedandCashReceivedDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#StockBasedCompensationIntrinsicValueofOptionsExercisedandCashReceivedDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/StockBasedCompensationIntrinsicValueofOptionsExercisedandCashReceivedDetails" xlink:type="extended" id="i5c308cce9be14135b452bae50e999050_StockBasedCompensationIntrinsicValueofOptionsExercisedandCashReceivedDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_6ecd72d2-d75e-41db-8351-a7edd4f62c42" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue_7a528a89-2226-4a90-9eb3-eb06c1db5f99" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_6ecd72d2-d75e-41db-8351-a7edd4f62c42" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue_7a528a89-2226-4a90-9eb3-eb06c1db5f99" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromStockOptionsExercised_f20b7514-a1ae-4d8c-a03b-3d4319a939d7" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ProceedsFromStockOptionsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_6ecd72d2-d75e-41db-8351-a7edd4f62c42" xlink:to="loc_us-gaap_ProceedsFromStockOptionsExercised_f20b7514-a1ae-4d8c-a03b-3d4319a939d7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_d7215878-543e-4d12-8739-9007d973807f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_6ecd72d2-d75e-41db-8351-a7edd4f62c42" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_d7215878-543e-4d12-8739-9007d973807f" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_d2521577-189f-4cd9-be24-1ef6e342e856" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_d7215878-543e-4d12-8739-9007d973807f" xlink:to="loc_us-gaap_AwardTypeAxis_d2521577-189f-4cd9-be24-1ef6e342e856" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_d2521577-189f-4cd9-be24-1ef6e342e856_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_d2521577-189f-4cd9-be24-1ef6e342e856" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_d2521577-189f-4cd9-be24-1ef6e342e856_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_725a351e-e99d-42c5-a6e0-697258b76668" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_d2521577-189f-4cd9-be24-1ef6e342e856" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_725a351e-e99d-42c5-a6e0-697258b76668" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_NonQualifiedStockOptionsMember_eac86db7-d2b0-42b8-94d4-78c9bd1797bb" xlink:href="nrg-20201231.xsd#nrg_NonQualifiedStockOptionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_725a351e-e99d-42c5-a6e0-697258b76668" xlink:to="loc_nrg_NonQualifiedStockOptionsMember_eac86db7-d2b0-42b8-94d4-78c9bd1797bb" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/StockBasedCompensationSupplementalInformationDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#StockBasedCompensationSupplementalInformationDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/StockBasedCompensationSupplementalInformationDetails" xlink:type="extended" id="i1e39244e0e264935abfd7c35ec12e7d4_StockBasedCompensationSupplementalInformationDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_53312fc6-0dcb-4512-8820-749c92bcb4ff" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation_6b4fb71b-138b-4edb-bf63-04ba3995b223" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_53312fc6-0dcb-4512-8820-749c92bcb4ff" xlink:to="loc_us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation_6b4fb71b-138b-4edb-bf63-04ba3995b223" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_30eba2de-376b-4838-aff0-b162609dccf1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AllocatedShareBasedCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_53312fc6-0dcb-4512-8820-749c92bcb4ff" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_30eba2de-376b-4838-aff0-b162609dccf1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense_a4db50af-2c7e-472d-9790-8bfd58d916e5" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_53312fc6-0dcb-4512-8820-749c92bcb4ff" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense_a4db50af-2c7e-472d-9790-8bfd58d916e5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_177fd45e-7655-471c-a301-f303f59dd640" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_53312fc6-0dcb-4512-8820-749c92bcb4ff" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_177fd45e-7655-471c-a301-f303f59dd640" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_49093d76-e42d-4e56-b5d3-a80d8f0f7c0b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_53312fc6-0dcb-4512-8820-749c92bcb4ff" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_49093d76-e42d-4e56-b5d3-a80d8f0f7c0b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_4b05686d-0758-49ac-9c6c-0dede37adb45" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_53312fc6-0dcb-4512-8820-749c92bcb4ff" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_4b05686d-0758-49ac-9c6c-0dede37adb45" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_6ffb8dde-7a41-4dee-94d5-be85c7cbb811" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_53312fc6-0dcb-4512-8820-749c92bcb4ff" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_6ffb8dde-7a41-4dee-94d5-be85c7cbb811" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_849dcaf3-b561-4c6e-a2fb-33bdbc702480" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_6ffb8dde-7a41-4dee-94d5-be85c7cbb811" xlink:to="loc_us-gaap_AwardTypeAxis_849dcaf3-b561-4c6e-a2fb-33bdbc702480" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_849dcaf3-b561-4c6e-a2fb-33bdbc702480_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_849dcaf3-b561-4c6e-a2fb-33bdbc702480" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_849dcaf3-b561-4c6e-a2fb-33bdbc702480_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_4ef45266-fcdb-4ee6-af58-16dca6f1f6ee" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_849dcaf3-b561-4c6e-a2fb-33bdbc702480" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_4ef45266-fcdb-4ee6-af58-16dca6f1f6ee" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_aef3f6ad-fb6d-40ed-ad06-7f093e53061d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_4ef45266-fcdb-4ee6-af58-16dca6f1f6ee" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_aef3f6ad-fb6d-40ed-ad06-7f093e53061d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_DeferredStockUnitsMember_1c3d1fdd-6ee7-4dd2-b729-73ebdd169738" xlink:href="nrg-20201231.xsd#nrg_DeferredStockUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_4ef45266-fcdb-4ee6-af58-16dca6f1f6ee" xlink:to="loc_nrg_DeferredStockUnitsMember_1c3d1fdd-6ee7-4dd2-b729-73ebdd169738" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_MarketStockUnitMember_9b80410c-7b15-4645-8bb2-bc9d46667649" xlink:href="nrg-20201231.xsd#nrg_MarketStockUnitMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_4ef45266-fcdb-4ee6-af58-16dca6f1f6ee" xlink:to="loc_nrg_MarketStockUnitMember_9b80410c-7b15-4645-8bb2-bc9d46667649" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_RelativePerformanceStockUnitsMember_87a72dbe-5466-4877-9bfd-a9875830410b" xlink:href="nrg-20201231.xsd#nrg_RelativePerformanceStockUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_4ef45266-fcdb-4ee6-af58-16dca6f1f6ee" xlink:to="loc_nrg_RelativePerformanceStockUnitsMember_87a72dbe-5466-4877-9bfd-a9875830410b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_PhantomRestrictedStockUnitsPRSUsMember_b95754b2-cd1a-4653-a3f0-865997249cff" xlink:href="nrg-20201231.xsd#nrg_PhantomRestrictedStockUnitsPRSUsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_4ef45266-fcdb-4ee6-af58-16dca6f1f6ee" xlink:to="loc_nrg_PhantomRestrictedStockUnitsPRSUsMember_b95754b2-cd1a-4653-a3f0-865997249cff" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/RelatedPartyTransactions" xlink:type="simple" xlink:href="nrg-20201231.xsd#RelatedPartyTransactions"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/RelatedPartyTransactions" xlink:type="extended" id="icc8871831d4a4756bfa6c23bfb3b99cd_RelatedPartyTransactions"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/RelatedPartyTransactionsTables" xlink:type="simple" xlink:href="nrg-20201231.xsd#RelatedPartyTransactionsTables"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/RelatedPartyTransactionsTables" xlink:type="extended" id="ia17520384fa04bad8c4c6b364acf9ffa_RelatedPartyTransactionsTables"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/RelatedPartyTransactionsSummaryofMaterialRelatedPartyTransactionsWithThirdPartyAffiliatesDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#RelatedPartyTransactionsSummaryofMaterialRelatedPartyTransactionsWithThirdPartyAffiliatesDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/RelatedPartyTransactionsSummaryofMaterialRelatedPartyTransactionsWithThirdPartyAffiliatesDetails" xlink:type="extended" id="i57bfefc127814e7985087cd4fb312a36_RelatedPartyTransactionsSummaryofMaterialRelatedPartyTransactionsWithThirdPartyAffiliatesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_445c9ac0-14f2-482f-8e58-197aed3342fb" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RelatedPartyTransactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromRelatedParties_43b23fc9-884a-404c-8218-a22e08cc4c21" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RevenueFromRelatedParties"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_445c9ac0-14f2-482f-8e58-197aed3342fb" xlink:to="loc_us-gaap_RevenueFromRelatedParties_43b23fc9-884a-404c-8218-a22e08cc4c21" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_af7cb576-559d-400b-b42e-7174078c1e4e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_445c9ac0-14f2-482f-8e58-197aed3342fb" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_af7cb576-559d-400b-b42e-7174078c1e4e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_5beb805b-64f7-42f5-b6ab-9979e9bdf7ca" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_af7cb576-559d-400b-b42e-7174078c1e4e" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_5beb805b-64f7-42f5-b6ab-9979e9bdf7ca" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_5beb805b-64f7-42f5-b6ab-9979e9bdf7ca_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_5beb805b-64f7-42f5-b6ab-9979e9bdf7ca" xlink:to="loc_us-gaap_RelatedPartyDomain_5beb805b-64f7-42f5-b6ab-9979e9bdf7ca_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_bedcef9a-4a52-4421-9358-6eecf9dfaa1e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_5beb805b-64f7-42f5-b6ab-9979e9bdf7ca" xlink:to="loc_us-gaap_RelatedPartyDomain_bedcef9a-4a52-4421-9358-6eecf9dfaa1e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_GladstonePowerStationMember_5852a473-d586-40b5-b0a8-9fe8c6b493bb" xlink:href="nrg-20201231.xsd#nrg_GladstonePowerStationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_bedcef9a-4a52-4421-9358-6eecf9dfaa1e" xlink:to="loc_nrg_GladstonePowerStationMember_5852a473-d586-40b5-b0a8-9fe8c6b493bb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_GenConnEnergyLlcMember_d617965f-fe93-4baa-8604-5e64cc8ca76c" xlink:href="nrg-20201231.xsd#nrg_GenConnEnergyLlcMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_bedcef9a-4a52-4421-9358-6eecf9dfaa1e" xlink:to="loc_nrg_GenConnEnergyLlcMember_d617965f-fe93-4baa-8604-5e64cc8ca76c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_IvanpahCreditAgreementMember_3bf9a6c0-a901-4bdf-be8c-c47ace31b3d6" xlink:href="nrg-20201231.xsd#nrg_IvanpahCreditAgreementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_bedcef9a-4a52-4421-9358-6eecf9dfaa1e" xlink:to="loc_nrg_IvanpahCreditAgreementMember_3bf9a6c0-a901-4bdf-be8c-c47ace31b3d6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_MidwaySunsetCogenerationCompanyMember_592760e1-2879-4693-81a1-fdb01c1129c1" xlink:href="nrg-20201231.xsd#nrg_MidwaySunsetCogenerationCompanyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_bedcef9a-4a52-4421-9358-6eecf9dfaa1e" xlink:to="loc_nrg_MidwaySunsetCogenerationCompanyMember_592760e1-2879-4693-81a1-fdb01c1129c1" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/RelatedPartyTransactionsServiceAgreementandTransitionServiceAgreementwithGeOnDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#RelatedPartyTransactionsServiceAgreementandTransitionServiceAgreementwithGeOnDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/RelatedPartyTransactionsServiceAgreementandTransitionServiceAgreementwithGeOnDetails" xlink:type="extended" id="id6093062dba94ee3b260a5fad1cc2f59_RelatedPartyTransactionsServiceAgreementandTransitionServiceAgreementwithGeOnDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_212ab99d-1a51-4ea1-9309-fd65221361ed" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RelatedPartyTransactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionSellingGeneralAndAdministrativeExpensesFromTransactionsWithRelatedParty_93c2bc45-c08f-4f01-89ea-732eee8c0da4" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RelatedPartyTransactionSellingGeneralAndAdministrativeExpensesFromTransactionsWithRelatedParty"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_212ab99d-1a51-4ea1-9309-fd65221361ed" xlink:to="loc_us-gaap_RelatedPartyTransactionSellingGeneralAndAdministrativeExpensesFromTransactionsWithRelatedParty_93c2bc45-c08f-4f01-89ea-732eee8c0da4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_3ec454aa-f188-4d7c-b809-1dc713bca501" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_212ab99d-1a51-4ea1-9309-fd65221361ed" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_3ec454aa-f188-4d7c-b809-1dc713bca501" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_56fd2fe8-49e0-4011-9729-7479d5483ed2" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_3ec454aa-f188-4d7c-b809-1dc713bca501" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_56fd2fe8-49e0-4011-9729-7479d5483ed2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_56fd2fe8-49e0-4011-9729-7479d5483ed2_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_56fd2fe8-49e0-4011-9729-7479d5483ed2" xlink:to="loc_us-gaap_RelatedPartyDomain_56fd2fe8-49e0-4011-9729-7479d5483ed2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_bcee38e2-9d4d-41ad-82c5-f920cd840811" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_56fd2fe8-49e0-4011-9729-7479d5483ed2" xlink:to="loc_us-gaap_RelatedPartyDomain_bcee38e2-9d4d-41ad-82c5-f920cd840811" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_AffiliatedEntityMember_16b6a526-9dc3-43d3-aee3-8fbff417fe9f" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_AffiliatedEntityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_bcee38e2-9d4d-41ad-82c5-f920cd840811" xlink:to="loc_srt_AffiliatedEntityMember_16b6a526-9dc3-43d3-aee3-8fbff417fe9f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionAxis_78f671e8-ed7f-4bf6-9576-d3f7f8708b6b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RelatedPartyTransactionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_3ec454aa-f188-4d7c-b809-1dc713bca501" xlink:to="loc_us-gaap_RelatedPartyTransactionAxis_78f671e8-ed7f-4bf6-9576-d3f7f8708b6b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain_78f671e8-ed7f-4bf6-9576-d3f7f8708b6b_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RelatedPartyTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis_78f671e8-ed7f-4bf6-9576-d3f7f8708b6b" xlink:to="loc_us-gaap_RelatedPartyTransactionDomain_78f671e8-ed7f-4bf6-9576-d3f7f8708b6b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain_2ce9b3a2-b395-4682-837b-4581ce8c1332" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RelatedPartyTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis_78f671e8-ed7f-4bf6-9576-d3f7f8708b6b" xlink:to="loc_us-gaap_RelatedPartyTransactionDomain_2ce9b3a2-b395-4682-837b-4581ce8c1332" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_TransitionServicesAgreementMember_0e950b36-4fe7-4456-b03d-88ee409f4e96" xlink:href="nrg-20201231.xsd#nrg_TransitionServicesAgreementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionDomain_2ce9b3a2-b395-4682-837b-4581ce8c1332" xlink:to="loc_nrg_TransitionServicesAgreementMember_0e950b36-4fe7-4456-b03d-88ee409f4e96" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringPlanAxis_b04e140f-155b-4932-9693-ba92d8e00306" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RestructuringPlanAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_3ec454aa-f188-4d7c-b809-1dc713bca501" xlink:to="loc_us-gaap_RestructuringPlanAxis_b04e140f-155b-4932-9693-ba92d8e00306" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringPlanDomain_b04e140f-155b-4932-9693-ba92d8e00306_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RestructuringPlanDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RestructuringPlanAxis_b04e140f-155b-4932-9693-ba92d8e00306" xlink:to="loc_us-gaap_RestructuringPlanDomain_b04e140f-155b-4932-9693-ba92d8e00306_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringPlanDomain_b3043d73-c2f1-42e4-84f2-b264babb09a7" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RestructuringPlanDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RestructuringPlanAxis_b04e140f-155b-4932-9693-ba92d8e00306" xlink:to="loc_us-gaap_RestructuringPlanDomain_b3043d73-c2f1-42e4-84f2-b264babb09a7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_RestructuringSupportAgreementMember_e5508f99-6cd4-483d-ba8e-6f4a4d16cf4e" xlink:href="nrg-20201231.xsd#nrg_RestructuringSupportAgreementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringPlanDomain_b3043d73-c2f1-42e4-84f2-b264babb09a7" xlink:to="loc_nrg_RestructuringSupportAgreementMember_e5508f99-6cd4-483d-ba8e-6f4a4d16cf4e" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/CommitmentsandContingencies" xlink:type="simple" xlink:href="nrg-20201231.xsd#CommitmentsandContingencies"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/CommitmentsandContingencies" xlink:type="extended" id="i46da88b937c7426180aabc55b2ce01dc_CommitmentsandContingencies"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/CommitmentsandContingenciesTables" xlink:type="simple" xlink:href="nrg-20201231.xsd#CommitmentsandContingenciesTables"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/CommitmentsandContingenciesTables" xlink:type="extended" id="i248390a53ce44d3e9e084b69bee2a29d_CommitmentsandContingenciesTables"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/CommitmentsandContingenciesTransportationandPurchasedPowerCommitmentsDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#CommitmentsandContingenciesTransportationandPurchasedPowerCommitmentsDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/CommitmentsandContingenciesTransportationandPurchasedPowerCommitmentsDetails" xlink:type="extended" id="i11f6130b0e404174a5d215f49b4ca191_CommitmentsandContingenciesTransportationandPurchasedPowerCommitmentsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_nrg_CommitmentAndContingencyLineItems_702e65b0-fcdc-48aa-8136-aeee23348820" xlink:href="nrg-20201231.xsd#nrg_CommitmentAndContingencyLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_LongTermPurchaseCommitmentPeriodExpense_0400ec52-8101-4b11-9e87-8b3b67e3cca7" xlink:href="nrg-20201231.xsd#nrg_LongTermPurchaseCommitmentPeriodExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_CommitmentAndContingencyLineItems_702e65b0-fcdc-48aa-8136-aeee23348820" xlink:to="loc_nrg_LongTermPurchaseCommitmentPeriodExpense_0400ec52-8101-4b11-9e87-8b3b67e3cca7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnrecordedUnconditionalPurchaseObligationAbstract_b43750e0-355e-47cf-9e39-56a3a18e15f9" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_UnrecordedUnconditionalPurchaseObligationAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nrg_CommitmentAndContingencyLineItems_702e65b0-fcdc-48aa-8136-aeee23348820" xlink:to="loc_us-gaap_UnrecordedUnconditionalPurchaseObligationAbstract_b43750e0-355e-47cf-9e39-56a3a18e15f9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnrecordedUnconditionalPurchaseObligationBalanceOnFirstAnniversary_d7852444-6175-4cf0-b080-72f39d06869f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_UnrecordedUnconditionalPurchaseObligationBalanceOnFirstAnniversary"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnrecordedUnconditionalPurchaseObligationAbstract_b43750e0-355e-47cf-9e39-56a3a18e15f9" xlink:to="loc_us-gaap_UnrecordedUnconditionalPurchaseObligationBalanceOnFirstAnniversary_d7852444-6175-4cf0-b080-72f39d06869f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnrecordedUnconditionalPurchaseObligationBalanceOnSecondAnniversary_8c9e6842-41a9-45f0-918c-c426ecdd029f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_UnrecordedUnconditionalPurchaseObligationBalanceOnSecondAnniversary"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnrecordedUnconditionalPurchaseObligationAbstract_b43750e0-355e-47cf-9e39-56a3a18e15f9" xlink:to="loc_us-gaap_UnrecordedUnconditionalPurchaseObligationBalanceOnSecondAnniversary_8c9e6842-41a9-45f0-918c-c426ecdd029f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnrecordedUnconditionalPurchaseObligationBalanceOnThirdAnniversary_f9e49608-2b0b-4770-9617-ab72190e0087" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_UnrecordedUnconditionalPurchaseObligationBalanceOnThirdAnniversary"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnrecordedUnconditionalPurchaseObligationAbstract_b43750e0-355e-47cf-9e39-56a3a18e15f9" xlink:to="loc_us-gaap_UnrecordedUnconditionalPurchaseObligationBalanceOnThirdAnniversary_f9e49608-2b0b-4770-9617-ab72190e0087" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnrecordedUnconditionalPurchaseObligationBalanceOnFourthAnniversary_b8de37d6-7995-48f0-964b-a81e7835c133" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_UnrecordedUnconditionalPurchaseObligationBalanceOnFourthAnniversary"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnrecordedUnconditionalPurchaseObligationAbstract_b43750e0-355e-47cf-9e39-56a3a18e15f9" xlink:to="loc_us-gaap_UnrecordedUnconditionalPurchaseObligationBalanceOnFourthAnniversary_b8de37d6-7995-48f0-964b-a81e7835c133" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnrecordedUnconditionalPurchaseObligationBalanceOnFifthAnniversary_32724c0b-266d-4bda-8034-86912d31e970" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_UnrecordedUnconditionalPurchaseObligationBalanceOnFifthAnniversary"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnrecordedUnconditionalPurchaseObligationAbstract_b43750e0-355e-47cf-9e39-56a3a18e15f9" xlink:to="loc_us-gaap_UnrecordedUnconditionalPurchaseObligationBalanceOnFifthAnniversary_32724c0b-266d-4bda-8034-86912d31e970" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnrecordedUnconditionalPurchaseObligationDueAfterFiveYears_4a998f94-f032-47b7-aa6c-9976f520ffb7" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_UnrecordedUnconditionalPurchaseObligationDueAfterFiveYears"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnrecordedUnconditionalPurchaseObligationAbstract_b43750e0-355e-47cf-9e39-56a3a18e15f9" xlink:to="loc_us-gaap_UnrecordedUnconditionalPurchaseObligationDueAfterFiveYears_4a998f94-f032-47b7-aa6c-9976f520ffb7" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnrecordedUnconditionalPurchaseObligationBalanceSheetAmount_6fcc1d82-45df-4d5f-9b88-a8a19edc183b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_UnrecordedUnconditionalPurchaseObligationBalanceSheetAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnrecordedUnconditionalPurchaseObligationAbstract_b43750e0-355e-47cf-9e39-56a3a18e15f9" xlink:to="loc_us-gaap_UnrecordedUnconditionalPurchaseObligationBalanceSheetAmount_6fcc1d82-45df-4d5f-9b88-a8a19edc183b" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_LongTermPurchaseCommitmentPeriodExpense_ba338487-e981-4db1-bb58-de8ddb06805c" xlink:href="nrg-20201231.xsd#nrg_LongTermPurchaseCommitmentPeriodExpense"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_CommitmentAndContingencyTable_deb9b495-4fad-49d3-8658-5e7426ee93bf" xlink:href="nrg-20201231.xsd#nrg_CommitmentAndContingencyTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_nrg_CommitmentAndContingencyLineItems_702e65b0-fcdc-48aa-8136-aeee23348820" xlink:to="loc_nrg_CommitmentAndContingencyTable_deb9b495-4fad-49d3-8658-5e7426ee93bf" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermPurchaseCommitmentByCategoryOfItemPurchasedAxis_ec80373b-aac9-4ae9-ae5d-40816366fd17" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongTermPurchaseCommitmentByCategoryOfItemPurchasedAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_nrg_CommitmentAndContingencyTable_deb9b495-4fad-49d3-8658-5e7426ee93bf" xlink:to="loc_us-gaap_LongTermPurchaseCommitmentByCategoryOfItemPurchasedAxis_ec80373b-aac9-4ae9-ae5d-40816366fd17" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermPurchaseCommitmentCategoryOfItemPurchasedDomain_ec80373b-aac9-4ae9-ae5d-40816366fd17_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongTermPurchaseCommitmentCategoryOfItemPurchasedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentByCategoryOfItemPurchasedAxis_ec80373b-aac9-4ae9-ae5d-40816366fd17" xlink:to="loc_us-gaap_LongTermPurchaseCommitmentCategoryOfItemPurchasedDomain_ec80373b-aac9-4ae9-ae5d-40816366fd17_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermPurchaseCommitmentCategoryOfItemPurchasedDomain_deb6c030-1a46-4a99-9452-6ae5aa0c0efc" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongTermPurchaseCommitmentCategoryOfItemPurchasedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentByCategoryOfItemPurchasedAxis_ec80373b-aac9-4ae9-ae5d-40816366fd17" xlink:to="loc_us-gaap_LongTermPurchaseCommitmentCategoryOfItemPurchasedDomain_deb6c030-1a46-4a99-9452-6ae5aa0c0efc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_CoalGasAndTransportationCommitmentsMember_d568e6b1-55cc-422d-946d-c1f1653691b1" xlink:href="nrg-20201231.xsd#nrg_CoalGasAndTransportationCommitmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentCategoryOfItemPurchasedDomain_deb6c030-1a46-4a99-9452-6ae5aa0c0efc" xlink:to="loc_nrg_CoalGasAndTransportationCommitmentsMember_d568e6b1-55cc-422d-946d-c1f1653691b1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_RenewablePurchasedPowerAgreementsMember_823d17e4-0df1-4c3b-b48e-b2b140b9bbe3" xlink:href="nrg-20201231.xsd#nrg_RenewablePurchasedPowerAgreementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentCategoryOfItemPurchasedDomain_deb6c030-1a46-4a99-9452-6ae5aa0c0efc" xlink:to="loc_nrg_RenewablePurchasedPowerAgreementsMember_823d17e4-0df1-4c3b-b48e-b2b140b9bbe3" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/CommitmentsandContingenciesNarrativeDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#CommitmentsandContingenciesNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/CommitmentsandContingenciesNarrativeDetails" xlink:type="extended" id="ia5e0f3d6367a4e4a8e785507fcc0df92_CommitmentsandContingenciesNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingenciesLineItems_aa8837ad-f817-442c-9877-8ed4cd2f9f66" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LossContingenciesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_NuclearInsurancePerIncidentCoverageLimit_90c33837-fd58-43d6-af7e-09d940c9d0db" xlink:href="nrg-20201231.xsd#nrg_NuclearInsurancePerIncidentCoverageLimit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_aa8837ad-f817-442c-9877-8ed4cd2f9f66" xlink:to="loc_nrg_NuclearInsurancePerIncidentCoverageLimit_90c33837-fd58-43d6-af7e-09d940c9d0db" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_NuclearInsuranceRequirementPerSite_c3fe7ecb-85a5-4aed-8214-9683ec6e7fc6" xlink:href="nrg-20201231.xsd#nrg_NuclearInsuranceRequirementPerSite"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_aa8837ad-f817-442c-9877-8ed4cd2f9f66" xlink:to="loc_nrg_NuclearInsuranceRequirementPerSite_c3fe7ecb-85a5-4aed-8214-9683ec6e7fc6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_NuclearInsuranceFinancialProtectionPoolValue_fff592f3-2d0d-4ed1-b4c0-00cf9460d807" xlink:href="nrg-20201231.xsd#nrg_NuclearInsuranceFinancialProtectionPoolValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_aa8837ad-f817-442c-9877-8ed4cd2f9f66" xlink:to="loc_nrg_NuclearInsuranceFinancialProtectionPoolValue_fff592f3-2d0d-4ed1-b4c0-00cf9460d807" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_NuclearInsuranceFinancialProtectionPoolMaximumAssessment_833eedef-4151-405f-95ae-4b37d1ec7fec" xlink:href="nrg-20201231.xsd#nrg_NuclearInsuranceFinancialProtectionPoolMaximumAssessment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_aa8837ad-f817-442c-9877-8ed4cd2f9f66" xlink:to="loc_nrg_NuclearInsuranceFinancialProtectionPoolMaximumAssessment_833eedef-4151-405f-95ae-4b37d1ec7fec" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_NuclearInsuranceFinancialProtectionPoolMaximumAssessmentAdministrativeFeeAsAPercent_ffecaef1-d331-4630-87e5-968838ec0f80" xlink:href="nrg-20201231.xsd#nrg_NuclearInsuranceFinancialProtectionPoolMaximumAssessmentAdministrativeFeeAsAPercent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_aa8837ad-f817-442c-9877-8ed4cd2f9f66" xlink:to="loc_nrg_NuclearInsuranceFinancialProtectionPoolMaximumAssessmentAdministrativeFeeAsAPercent_ffecaef1-d331-4630-87e5-968838ec0f80" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_NuclearInsuranceFinancialProtectionPoolMaximumAnnualAssessment_7f5ead08-3378-476f-bb07-c46425b12f82" xlink:href="nrg-20201231.xsd#nrg_NuclearInsuranceFinancialProtectionPoolMaximumAnnualAssessment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_aa8837ad-f817-442c-9877-8ed4cd2f9f66" xlink:to="loc_nrg_NuclearInsuranceFinancialProtectionPoolMaximumAnnualAssessment_7f5ead08-3378-476f-bb07-c46425b12f82" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_FortyFourPercentMaximumAssessment_8b0d88c1-50f3-4c7a-acb4-d1686807ee13" xlink:href="nrg-20201231.xsd#nrg_FortyFourPercentMaximumAssessment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_aa8837ad-f817-442c-9877-8ed4cd2f9f66" xlink:to="loc_nrg_FortyFourPercentMaximumAssessment_8b0d88c1-50f3-4c7a-acb4-d1686807ee13" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_NuclearInsuranceFinancialProtectionPoolNuclearOperatorMaximumAnnualAssessment_7bc8da38-76a7-4ff0-9762-27ffc83bf6ed" xlink:href="nrg-20201231.xsd#nrg_NuclearInsuranceFinancialProtectionPoolNuclearOperatorMaximumAnnualAssessment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_aa8837ad-f817-442c-9877-8ed4cd2f9f66" xlink:to="loc_nrg_NuclearInsuranceFinancialProtectionPoolNuclearOperatorMaximumAnnualAssessment_7bc8da38-76a7-4ff0-9762-27ffc83bf6ed" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_NuclearInsuranceFinancialProtectionPoolNuclearOperatorTotalAssessment_d6758827-cff4-467d-99f9-ee7b6f246fab" xlink:href="nrg-20201231.xsd#nrg_NuclearInsuranceFinancialProtectionPoolNuclearOperatorTotalAssessment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_aa8837ad-f817-442c-9877-8ed4cd2f9f66" xlink:to="loc_nrg_NuclearInsuranceFinancialProtectionPoolNuclearOperatorTotalAssessment_d6758827-cff4-467d-99f9-ee7b6f246fab" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_MutualPropertyInsuranceTotalPropertyCoverage_f3c04c4a-9b85-4fb6-b834-275b9636519c" xlink:href="nrg-20201231.xsd#nrg_MutualPropertyInsuranceTotalPropertyCoverage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_aa8837ad-f817-442c-9877-8ed4cd2f9f66" xlink:to="loc_nrg_MutualPropertyInsuranceTotalPropertyCoverage_f3c04c4a-9b85-4fb6-b834-275b9636519c" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_MutualPropertyInsuranceAdditionalBlanketPolicyPropertyCoverage_38b375ce-19dc-4500-bfc2-f5308d170567" xlink:href="nrg-20201231.xsd#nrg_MutualPropertyInsuranceAdditionalBlanketPolicyPropertyCoverage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_aa8837ad-f817-442c-9877-8ed4cd2f9f66" xlink:to="loc_nrg_MutualPropertyInsuranceAdditionalBlanketPolicyPropertyCoverage_38b375ce-19dc-4500-bfc2-f5308d170567" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_MutualPropertyInsuranceIndividualMaximumPropertyCoverageLimit_39d91e5e-78af-41dc-a7ae-ac451b912e97" xlink:href="nrg-20201231.xsd#nrg_MutualPropertyInsuranceIndividualMaximumPropertyCoverageLimit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_aa8837ad-f817-442c-9877-8ed4cd2f9f66" xlink:to="loc_nrg_MutualPropertyInsuranceIndividualMaximumPropertyCoverageLimit_39d91e5e-78af-41dc-a7ae-ac451b912e97" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_MutualLostRevenueInsuranceMaximumWeeklyRecovery_fedce43e-cc00-4d68-85ca-d4375a097e01" xlink:href="nrg-20201231.xsd#nrg_MutualLostRevenueInsuranceMaximumWeeklyRecovery"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_aa8837ad-f817-442c-9877-8ed4cd2f9f66" xlink:to="loc_nrg_MutualLostRevenueInsuranceMaximumWeeklyRecovery_fedce43e-cc00-4d68-85ca-d4375a097e01" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_AdditionalMutualLostRevenueInsuranceWeeklyMaximum_0286b8d1-af58-46f7-bcfb-3dc960155733" xlink:href="nrg-20201231.xsd#nrg_AdditionalMutualLostRevenueInsuranceWeeklyMaximum"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_aa8837ad-f817-442c-9877-8ed4cd2f9f66" xlink:to="loc_nrg_AdditionalMutualLostRevenueInsuranceWeeklyMaximum_0286b8d1-af58-46f7-bcfb-3dc960155733" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_IndustryMutualInsuranceCompanyMultiplier_5e3b3216-caf7-4efe-bbd6-5a270df7712d" xlink:href="nrg-20201231.xsd#nrg_IndustryMutualInsuranceCompanyMultiplier"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_aa8837ad-f817-442c-9877-8ed4cd2f9f66" xlink:to="loc_nrg_IndustryMutualInsuranceCompanyMultiplier_5e3b3216-caf7-4efe-bbd6-5a270df7712d" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_Periodofretrospectivepremiumadjustments_3ff7ee4f-22cb-41b5-9cda-57e996cf4328" xlink:href="nrg-20201231.xsd#nrg_Periodofretrospectivepremiumadjustments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_aa8837ad-f817-442c-9877-8ed4cd2f9f66" xlink:to="loc_nrg_Periodofretrospectivepremiumadjustments_3ff7ee4f-22cb-41b5-9cda-57e996cf4328" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_NumberOfYearsBoardOfDirectorsOfIndustryMutualInsuranceCompanyCanAdjustPolicyAfterPolicyExpires_df14b349-8b9a-47f9-88fd-a1d729df5bc2" xlink:href="nrg-20201231.xsd#nrg_NumberOfYearsBoardOfDirectorsOfIndustryMutualInsuranceCompanyCanAdjustPolicyAfterPolicyExpires"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_aa8837ad-f817-442c-9877-8ed4cd2f9f66" xlink:to="loc_nrg_NumberOfYearsBoardOfDirectorsOfIndustryMutualInsuranceCompanyCanAdjustPolicyAfterPolicyExpires_df14b349-8b9a-47f9-88fd-a1d729df5bc2" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_NumberOfFacilities_55deb42b-4302-434a-b557-a4df4d7aaed0" xlink:href="nrg-20201231.xsd#nrg_NumberOfFacilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_aa8837ad-f817-442c-9877-8ed4cd2f9f66" xlink:to="loc_nrg_NumberOfFacilities_55deb42b-4302-434a-b557-a4df4d7aaed0" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingencyPendingClaimsNumber_28f7f4d9-8832-4c87-8700-86821cceecdc" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LossContingencyPendingClaimsNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_aa8837ad-f817-442c-9877-8ed4cd2f9f66" xlink:to="loc_us-gaap_LossContingencyPendingClaimsNumber_28f7f4d9-8832-4c87-8700-86821cceecdc" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingenciesTable_269012b6-b05d-4460-b69b-513c47877228" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LossContingenciesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LossContingenciesLineItems_aa8837ad-f817-442c-9877-8ed4cd2f9f66" xlink:to="loc_us-gaap_LossContingenciesTable_269012b6-b05d-4460-b69b-513c47877228" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingenciesByNatureOfContingencyAxis_03566c5d-5b1b-41c7-8fb7-31f55f531a72" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LossContingenciesByNatureOfContingencyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_269012b6-b05d-4460-b69b-513c47877228" xlink:to="loc_us-gaap_LossContingenciesByNatureOfContingencyAxis_03566c5d-5b1b-41c7-8fb7-31f55f531a72" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingencyNatureDomain_03566c5d-5b1b-41c7-8fb7-31f55f531a72_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LossContingencyNatureDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LossContingenciesByNatureOfContingencyAxis_03566c5d-5b1b-41c7-8fb7-31f55f531a72" xlink:to="loc_us-gaap_LossContingencyNatureDomain_03566c5d-5b1b-41c7-8fb7-31f55f531a72_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingencyNatureDomain_c4a4803a-9aec-4a3d-95e8-0bf328c2be0e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LossContingencyNatureDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LossContingenciesByNatureOfContingencyAxis_03566c5d-5b1b-41c7-8fb7-31f55f531a72" xlink:to="loc_us-gaap_LossContingencyNatureDomain_c4a4803a-9aec-4a3d-95e8-0bf328c2be0e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_NuclearEventMember_2ce09b40-137e-4fc5-856e-01d8dfb1aa3e" xlink:href="nrg-20201231.xsd#nrg_NuclearEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingencyNatureDomain_c4a4803a-9aec-4a3d-95e8-0bf328c2be0e" xlink:to="loc_nrg_NuclearEventMember_2ce09b40-137e-4fc5-856e-01d8dfb1aa3e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_NonnuclearEventMember_4f7633f1-a313-4d50-94e9-e0326c5f21ba" xlink:href="nrg-20201231.xsd#nrg_NonnuclearEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingencyNatureDomain_c4a4803a-9aec-4a3d-95e8-0bf328c2be0e" xlink:to="loc_nrg_NonnuclearEventMember_4f7633f1-a313-4d50-94e9-e0326c5f21ba" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_6bedf7b9-db2d-419b-b608-b08211a442d5" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_269012b6-b05d-4460-b69b-513c47877228" xlink:to="loc_srt_RangeAxis_6bedf7b9-db2d-419b-b608-b08211a442d5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_6bedf7b9-db2d-419b-b608-b08211a442d5_default" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_6bedf7b9-db2d-419b-b608-b08211a442d5" xlink:to="loc_srt_RangeMember_6bedf7b9-db2d-419b-b608-b08211a442d5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_baf6fbd2-d965-48ab-bc13-213a91d9e262" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_6bedf7b9-db2d-419b-b608-b08211a442d5" xlink:to="loc_srt_RangeMember_baf6fbd2-d965-48ab-bc13-213a91d9e262" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_9494b04b-82a1-46c6-961b-9bce44a77b47" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_baf6fbd2-d965-48ab-bc13-213a91d9e262" xlink:to="loc_srt_MaximumMember_9494b04b-82a1-46c6-961b-9bce44a77b47" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_e4e42d77-4e58-46d5-9879-68748e6d3592" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_baf6fbd2-d965-48ab-bc13-213a91d9e262" xlink:to="loc_srt_MinimumMember_e4e42d77-4e58-46d5-9879-68748e6d3592" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseAxis_4b64068c-ec62-4c47-a009-e9a6fe99c61e" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_LitigationCaseAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_269012b6-b05d-4460-b69b-513c47877228" xlink:to="loc_srt_LitigationCaseAxis_4b64068c-ec62-4c47-a009-e9a6fe99c61e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseTypeDomain_4b64068c-ec62-4c47-a009-e9a6fe99c61e_default" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_LitigationCaseTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_LitigationCaseAxis_4b64068c-ec62-4c47-a009-e9a6fe99c61e" xlink:to="loc_srt_LitigationCaseTypeDomain_4b64068c-ec62-4c47-a009-e9a6fe99c61e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseTypeDomain_f9ce28d8-830d-4cd8-bf6c-b0bc52714cb9" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_LitigationCaseTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_LitigationCaseAxis_4b64068c-ec62-4c47-a009-e9a6fe99c61e" xlink:to="loc_srt_LitigationCaseTypeDomain_f9ce28d8-830d-4cd8-bf6c-b0bc52714cb9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_SierraClubEtAlVMidwestGenerationLLCMember_56afb61d-2c2b-4e22-baf0-5ee376ff355e" xlink:href="nrg-20201231.xsd#nrg_SierraClubEtAlVMidwestGenerationLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_LitigationCaseTypeDomain_f9ce28d8-830d-4cd8-bf6c-b0bc52714cb9" xlink:to="loc_nrg_SierraClubEtAlVMidwestGenerationLLCMember_56afb61d-2c2b-4e22-baf0-5ee376ff355e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_XOOMEnergyLitigationMember_09c116ba-475a-4b08-aecf-d4fe94f7d76e" xlink:href="nrg-20201231.xsd#nrg_XOOMEnergyLitigationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_LitigationCaseTypeDomain_f9ce28d8-830d-4cd8-bf6c-b0bc52714cb9" xlink:to="loc_nrg_XOOMEnergyLitigationMember_09c116ba-475a-4b08-aecf-d4fe94f7d76e" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/RegulatoryMatters" xlink:type="simple" xlink:href="nrg-20201231.xsd#RegulatoryMatters"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/RegulatoryMatters" xlink:type="extended" id="if150d10618144756a2130719aa8cbdcb_RegulatoryMatters"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/RegulatoryMattersDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#RegulatoryMattersDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/RegulatoryMattersDetails" xlink:type="extended" id="if53cf5725adc4396b808513446fca993_RegulatoryMattersDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventLineItems_df69d060-31b2-41fa-beb8-f54da458c3a2" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LitigationSettlementAmountAwardedToOtherParty_eb4d5305-50b5-42e7-88c3-aad7ab7b0058" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LitigationSettlementAmountAwardedToOtherParty"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_df69d060-31b2-41fa-beb8-f54da458c3a2" xlink:to="loc_us-gaap_LitigationSettlementAmountAwardedToOtherParty_eb4d5305-50b5-42e7-88c3-aad7ab7b0058" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTable_3a322340-333c-45d2-8959-0c8bb6bd1fc4" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SubsequentEventLineItems_df69d060-31b2-41fa-beb8-f54da458c3a2" xlink:to="loc_us-gaap_SubsequentEventTable_3a322340-333c-45d2-8959-0c8bb6bd1fc4" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_6657957d-b1f6-4456-ac95-f474c7434794" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_3a322340-333c-45d2-8959-0c8bb6bd1fc4" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_6657957d-b1f6-4456-ac95-f474c7434794" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_6657957d-b1f6-4456-ac95-f474c7434794_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_6657957d-b1f6-4456-ac95-f474c7434794" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_6657957d-b1f6-4456-ac95-f474c7434794_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_d226ef55-571c-4202-9247-1c1dd10c7340" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_6657957d-b1f6-4456-ac95-f474c7434794" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_d226ef55-571c-4202-9247-1c1dd10c7340" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_0ee71fe0-cf17-40b5-880e-9aefa8d82712" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_d226ef55-571c-4202-9247-1c1dd10c7340" xlink:to="loc_us-gaap_SubsequentEventMember_0ee71fe0-cf17-40b5-880e-9aefa8d82712" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/EnvironmentalMatters" xlink:type="simple" xlink:href="nrg-20201231.xsd#EnvironmentalMatters"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/EnvironmentalMatters" xlink:type="extended" id="i3820e4551d204f09a9142c8cc5dc906f_EnvironmentalMatters"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/CashFlowInformation" xlink:type="simple" xlink:href="nrg-20201231.xsd#CashFlowInformation"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/CashFlowInformation" xlink:type="extended" id="ic2ceb323f728437bacfe2d287bbead56_CashFlowInformation"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/CashFlowInformationTables" xlink:type="simple" xlink:href="nrg-20201231.xsd#CashFlowInformationTables"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/CashFlowInformationTables" xlink:type="extended" id="i0a3304bac771407a990ee3151ec7e7a3_CashFlowInformationTables"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/CashFlowInformationDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#CashFlowInformationDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/CashFlowInformationDetails" xlink:type="extended" id="i4f439eb73c5447d4a1ab8db96a8c2324_CashFlowInformationDetails"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/Guarantees" xlink:type="simple" xlink:href="nrg-20201231.xsd#Guarantees"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/Guarantees" xlink:type="extended" id="i321fab87168044fd88ef177c02282126_Guarantees"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/GuaranteesTables" xlink:type="simple" xlink:href="nrg-20201231.xsd#GuaranteesTables"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/GuaranteesTables" xlink:type="extended" id="i0660f109aaa54106aab9f1da083a33b6_GuaranteesTables"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/GuaranteesScheduleofMaximumPotentialExposureDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#GuaranteesScheduleofMaximumPotentialExposureDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/GuaranteesScheduleofMaximumPotentialExposureDetails" xlink:type="extended" id="ic9726b04e33c46a0895bbfafadc09a78_GuaranteesScheduleofMaximumPotentialExposureDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GuaranteeObligationsLineItems_3e609f35-f42b-4196-95fd-ddf9d988186f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GuaranteeObligationsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_GuaranteeMaturityLessThanOneYear_48e628e8-327c-4017-b01c-3c1d4df85359" xlink:href="nrg-20201231.xsd#nrg_GuaranteeMaturityLessThanOneYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GuaranteeObligationsLineItems_3e609f35-f42b-4196-95fd-ddf9d988186f" xlink:to="loc_nrg_GuaranteeMaturityLessThanOneYear_48e628e8-327c-4017-b01c-3c1d4df85359" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_GuaranteeMaturityBetweenOneToThreeYears_11fae3d2-ea9c-4937-bb95-d3ba3ed1e242" xlink:href="nrg-20201231.xsd#nrg_GuaranteeMaturityBetweenOneToThreeYears"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GuaranteeObligationsLineItems_3e609f35-f42b-4196-95fd-ddf9d988186f" xlink:to="loc_nrg_GuaranteeMaturityBetweenOneToThreeYears_11fae3d2-ea9c-4937-bb95-d3ba3ed1e242" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_GuaranteeMaturityBetweenThreeToFiveYears_36c64603-5fb3-478e-92fa-dc7ef51f5b63" xlink:href="nrg-20201231.xsd#nrg_GuaranteeMaturityBetweenThreeToFiveYears"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GuaranteeObligationsLineItems_3e609f35-f42b-4196-95fd-ddf9d988186f" xlink:to="loc_nrg_GuaranteeMaturityBetweenThreeToFiveYears_36c64603-5fb3-478e-92fa-dc7ef51f5b63" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_GuaranteeMaturityGreaterThanFiveYears_60eeac9b-500f-4c10-ac8a-cd0b3bfff0b0" xlink:href="nrg-20201231.xsd#nrg_GuaranteeMaturityGreaterThanFiveYears"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GuaranteeObligationsLineItems_3e609f35-f42b-4196-95fd-ddf9d988186f" xlink:to="loc_nrg_GuaranteeMaturityGreaterThanFiveYears_60eeac9b-500f-4c10-ac8a-cd0b3bfff0b0" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_GuaranteeObligationsEstimatedExposure_fa57f7c9-10ef-4f32-8412-87a745702882" xlink:href="nrg-20201231.xsd#nrg_GuaranteeObligationsEstimatedExposure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GuaranteeObligationsLineItems_3e609f35-f42b-4196-95fd-ddf9d988186f" xlink:to="loc_nrg_GuaranteeObligationsEstimatedExposure_fa57f7c9-10ef-4f32-8412-87a745702882" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfGuaranteeObligationsTable_709f3d0e-bab3-46f9-9617-d988aac0b216" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfGuaranteeObligationsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_GuaranteeObligationsLineItems_3e609f35-f42b-4196-95fd-ddf9d988186f" xlink:to="loc_us-gaap_ScheduleOfGuaranteeObligationsTable_709f3d0e-bab3-46f9-9617-d988aac0b216" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GuaranteeObligationsByNatureAxis_b0a6b04b-0d3d-4a4e-b944-b174cead964b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GuaranteeObligationsByNatureAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfGuaranteeObligationsTable_709f3d0e-bab3-46f9-9617-d988aac0b216" xlink:to="loc_us-gaap_GuaranteeObligationsByNatureAxis_b0a6b04b-0d3d-4a4e-b944-b174cead964b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GuaranteeObligationsNatureDomain_b0a6b04b-0d3d-4a4e-b944-b174cead964b_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GuaranteeObligationsNatureDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_GuaranteeObligationsByNatureAxis_b0a6b04b-0d3d-4a4e-b944-b174cead964b" xlink:to="loc_us-gaap_GuaranteeObligationsNatureDomain_b0a6b04b-0d3d-4a4e-b944-b174cead964b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GuaranteeObligationsNatureDomain_bc0bcc27-9aa8-4026-a67c-fdac91c86969" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GuaranteeObligationsNatureDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_GuaranteeObligationsByNatureAxis_b0a6b04b-0d3d-4a4e-b944-b174cead964b" xlink:to="loc_us-gaap_GuaranteeObligationsNatureDomain_bc0bcc27-9aa8-4026-a67c-fdac91c86969" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_LettersOfCreditAndSuretyBondsMember_85136000-15ee-4873-aeca-9d35ce5ae89f" xlink:href="nrg-20201231.xsd#nrg_LettersOfCreditAndSuretyBondsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GuaranteeObligationsNatureDomain_bc0bcc27-9aa8-4026-a67c-fdac91c86969" xlink:to="loc_nrg_LettersOfCreditAndSuretyBondsMember_85136000-15ee-4873-aeca-9d35ce5ae89f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_AssetSalesGuaranteeObligationsMember_f1121ca0-03cc-4234-9810-5a1da141fdf6" xlink:href="nrg-20201231.xsd#nrg_AssetSalesGuaranteeObligationsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GuaranteeObligationsNatureDomain_bc0bcc27-9aa8-4026-a67c-fdac91c86969" xlink:to="loc_nrg_AssetSalesGuaranteeObligationsMember_f1121ca0-03cc-4234-9810-5a1da141fdf6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GuaranteeTypeOtherMember_1bab2fea-a1d3-4f1a-947c-c6b28b8a2e83" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GuaranteeTypeOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GuaranteeObligationsNatureDomain_bc0bcc27-9aa8-4026-a67c-fdac91c86969" xlink:to="loc_us-gaap_GuaranteeTypeOtherMember_1bab2fea-a1d3-4f1a-947c-c6b28b8a2e83" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/GuaranteesNarrativeDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#GuaranteesNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/GuaranteesNarrativeDetails" xlink:type="extended" id="i3e00201efce549029c38243dc75817d8_GuaranteesNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GuaranteeObligationsLineItems_c4102cf8-e291-4e35-9662-e336e1eeb9e7" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GuaranteeObligationsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_GuaranteeObligationsEstimatedExposure_0095731b-5c50-4645-b33c-5924c0fbc9a4" xlink:href="nrg-20201231.xsd#nrg_GuaranteeObligationsEstimatedExposure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GuaranteeObligationsLineItems_c4102cf8-e291-4e35-9662-e336e1eeb9e7" xlink:to="loc_nrg_GuaranteeObligationsEstimatedExposure_0095731b-5c50-4645-b33c-5924c0fbc9a4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_GuaranteeObligationsLettersofCreditandSuretyBondsMaximumExpirationPeriod_b64a1823-a38e-4728-8484-653e626a6984" xlink:href="nrg-20201231.xsd#nrg_GuaranteeObligationsLettersofCreditandSuretyBondsMaximumExpirationPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GuaranteeObligationsLineItems_c4102cf8-e291-4e35-9662-e336e1eeb9e7" xlink:to="loc_nrg_GuaranteeObligationsLettersofCreditandSuretyBondsMaximumExpirationPeriod_b64a1823-a38e-4728-8484-653e626a6984" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GuaranteeObligationsCurrentCarryingValue_0124efec-697c-406a-a7b7-af5873c02165" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GuaranteeObligationsCurrentCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GuaranteeObligationsLineItems_c4102cf8-e291-4e35-9662-e336e1eeb9e7" xlink:to="loc_us-gaap_GuaranteeObligationsCurrentCarryingValue_0124efec-697c-406a-a7b7-af5873c02165" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfGuaranteeObligationsTable_517f6aa9-86b3-4266-ab09-5115b5199706" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfGuaranteeObligationsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_GuaranteeObligationsLineItems_c4102cf8-e291-4e35-9662-e336e1eeb9e7" xlink:to="loc_us-gaap_ScheduleOfGuaranteeObligationsTable_517f6aa9-86b3-4266-ab09-5115b5199706" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GuaranteeObligationsByNatureAxis_218488dc-4199-4778-a8cd-6e23a26cc4a7" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GuaranteeObligationsByNatureAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfGuaranteeObligationsTable_517f6aa9-86b3-4266-ab09-5115b5199706" xlink:to="loc_us-gaap_GuaranteeObligationsByNatureAxis_218488dc-4199-4778-a8cd-6e23a26cc4a7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GuaranteeObligationsNatureDomain_218488dc-4199-4778-a8cd-6e23a26cc4a7_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GuaranteeObligationsNatureDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_GuaranteeObligationsByNatureAxis_218488dc-4199-4778-a8cd-6e23a26cc4a7" xlink:to="loc_us-gaap_GuaranteeObligationsNatureDomain_218488dc-4199-4778-a8cd-6e23a26cc4a7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GuaranteeObligationsNatureDomain_7075b0bc-777c-49e4-ba46-61d8ccd87dfb" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GuaranteeObligationsNatureDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_GuaranteeObligationsByNatureAxis_218488dc-4199-4778-a8cd-6e23a26cc4a7" xlink:to="loc_us-gaap_GuaranteeObligationsNatureDomain_7075b0bc-777c-49e4-ba46-61d8ccd87dfb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_LettersOfCreditAndSuretyBondsMember_540f89bc-5810-4e7b-a7a1-18d163e2eb37" xlink:href="nrg-20201231.xsd#nrg_LettersOfCreditAndSuretyBondsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GuaranteeObligationsNatureDomain_7075b0bc-777c-49e4-ba46-61d8ccd87dfb" xlink:to="loc_nrg_LettersOfCreditAndSuretyBondsMember_540f89bc-5810-4e7b-a7a1-18d163e2eb37" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_AssetSalesGuaranteeObligationsMember_e66e7522-e5f2-4225-ad94-c5e9dbfb12fb" xlink:href="nrg-20201231.xsd#nrg_AssetSalesGuaranteeObligationsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GuaranteeObligationsNatureDomain_7075b0bc-777c-49e4-ba46-61d8ccd87dfb" xlink:to="loc_nrg_AssetSalesGuaranteeObligationsMember_e66e7522-e5f2-4225-ad94-c5e9dbfb12fb" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/JointlyOwnedPlants" xlink:type="simple" xlink:href="nrg-20201231.xsd#JointlyOwnedPlants"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/JointlyOwnedPlants" xlink:type="extended" id="iecaaa1c3e4ee4086987adaa869774a0c_JointlyOwnedPlants"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/JointlyOwnedPlantsTables" xlink:type="simple" xlink:href="nrg-20201231.xsd#JointlyOwnedPlantsTables"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/JointlyOwnedPlantsTables" xlink:type="extended" id="icb6365f0ba2a435384438e56d5a40f34_JointlyOwnedPlantsTables"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/JointlyOwnedPlantsDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#JointlyOwnedPlantsDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/JointlyOwnedPlantsDetails" xlink:type="extended" id="i4130692d446c4bc793588d7526b476ef_JointlyOwnedPlantsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_JointlyOwnedUtilityPlantInterestsLineItems_1f50991e-4ee8-42e0-81d5-53fda98a4640" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_JointlyOwnedUtilityPlantInterestsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_JointlyOwnedUtilityPlantProportionateOwnershipShare_b1428fc8-75f2-4b42-898d-623383163b52" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_JointlyOwnedUtilityPlantProportionateOwnershipShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_JointlyOwnedUtilityPlantInterestsLineItems_1f50991e-4ee8-42e0-81d5-53fda98a4640" xlink:to="loc_us-gaap_JointlyOwnedUtilityPlantProportionateOwnershipShare_b1428fc8-75f2-4b42-898d-623383163b52" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_JointlyOwnedUtilityPlantGrossOwnershipAmountOfPlantInService_5b8769fd-9bc3-495d-8258-a8c28309e05b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_JointlyOwnedUtilityPlantGrossOwnershipAmountOfPlantInService"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_JointlyOwnedUtilityPlantInterestsLineItems_1f50991e-4ee8-42e0-81d5-53fda98a4640" xlink:to="loc_us-gaap_JointlyOwnedUtilityPlantGrossOwnershipAmountOfPlantInService_5b8769fd-9bc3-495d-8258-a8c28309e05b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfPlantAccumulatedDepreciation_2b5d55a4-bc57-4d53-b300-0ec2bb51b462" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfPlantAccumulatedDepreciation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_JointlyOwnedUtilityPlantInterestsLineItems_1f50991e-4ee8-42e0-81d5-53fda98a4640" xlink:to="loc_us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfPlantAccumulatedDepreciation_2b5d55a4-bc57-4d53-b300-0ec2bb51b462" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfConstructionWorkInProgress_a3f01877-5b6c-49b8-a304-421eb07fdb15" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfConstructionWorkInProgress"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_JointlyOwnedUtilityPlantInterestsLineItems_1f50991e-4ee8-42e0-81d5-53fda98a4640" xlink:to="loc_us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfConstructionWorkInProgress_a3f01877-5b6c-49b8-a304-421eb07fdb15" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_JointlyOwnedUtilityPlantInterestsTable_942089a4-cabb-469b-b90e-68822315c3c1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_JointlyOwnedUtilityPlantInterestsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_JointlyOwnedUtilityPlantInterestsLineItems_1f50991e-4ee8-42e0-81d5-53fda98a4640" xlink:to="loc_us-gaap_JointlyOwnedUtilityPlantInterestsTable_942089a4-cabb-469b-b90e-68822315c3c1" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_JointlyOwnedUtilityPlantAxis_784afa75-713d-4faa-b3ab-137cd685c13d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_JointlyOwnedUtilityPlantAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_JointlyOwnedUtilityPlantInterestsTable_942089a4-cabb-469b-b90e-68822315c3c1" xlink:to="loc_us-gaap_JointlyOwnedUtilityPlantAxis_784afa75-713d-4faa-b3ab-137cd685c13d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_JointlyOwnedUtilityPlantDomain_784afa75-713d-4faa-b3ab-137cd685c13d_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_JointlyOwnedUtilityPlantDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_JointlyOwnedUtilityPlantAxis_784afa75-713d-4faa-b3ab-137cd685c13d" xlink:to="loc_us-gaap_JointlyOwnedUtilityPlantDomain_784afa75-713d-4faa-b3ab-137cd685c13d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_JointlyOwnedUtilityPlantDomain_580ed6e0-ace5-4025-a238-420528891752" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_JointlyOwnedUtilityPlantDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_JointlyOwnedUtilityPlantAxis_784afa75-713d-4faa-b3ab-137cd685c13d" xlink:to="loc_us-gaap_JointlyOwnedUtilityPlantDomain_580ed6e0-ace5-4025-a238-420528891752" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_SouthTexasProjectUnits1And2Member_2cab5c04-445c-4a24-a4c7-540a99dab4d1" xlink:href="nrg-20201231.xsd#nrg_SouthTexasProjectUnits1And2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_JointlyOwnedUtilityPlantDomain_580ed6e0-ace5-4025-a238-420528891752" xlink:to="loc_nrg_SouthTexasProjectUnits1And2Member_2cab5c04-445c-4a24-a4c7-540a99dab4d1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nrg_CedarBayouUnit4Member_d749945c-610a-488d-9c4e-be8aae190a99" xlink:href="nrg-20201231.xsd#nrg_CedarBayouUnit4Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_JointlyOwnedUtilityPlantDomain_580ed6e0-ace5-4025-a238-420528891752" xlink:to="loc_nrg_CedarBayouUnit4Member_d749945c-610a-488d-9c4e-be8aae190a99" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/SCHEDULEIIVALUATIONANDQUALIFYINGACCOUNTS" xlink:type="simple" xlink:href="nrg-20201231.xsd#SCHEDULEIIVALUATIONANDQUALIFYINGACCOUNTS"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/SCHEDULEIIVALUATIONANDQUALIFYINGACCOUNTS" xlink:type="extended" id="if437abd992ca416a8f17f2c13cae089d_SCHEDULEIIVALUATIONANDQUALIFYINGACCOUNTS"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/SCHEDULEIIVALUATIONANDQUALIFYINGACCOUNTSTables" xlink:type="simple" xlink:href="nrg-20201231.xsd#SCHEDULEIIVALUATIONANDQUALIFYINGACCOUNTSTables"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/SCHEDULEIIVALUATIONANDQUALIFYINGACCOUNTSTables" xlink:type="extended" id="i7800c12c609041be957b388933a365e5_SCHEDULEIIVALUATIONANDQUALIFYINGACCOUNTSTables"/>
  <link:roleRef roleURI="http://www.nrgenergy.com/role/SCHEDULEIIVALUATIONANDQUALIFYINGACCOUNTSDetails" xlink:type="simple" xlink:href="nrg-20201231.xsd#SCHEDULEIIVALUATIONANDQUALIFYINGACCOUNTSDetails"/>
  <link:definitionLink xlink:role="http://www.nrgenergy.com/role/SCHEDULEIIVALUATIONANDQUALIFYINGACCOUNTSDetails" xlink:type="extended" id="ic6340c6c444b48c18ef63578be67fdb3_SCHEDULEIIVALUATIONANDQUALIFYINGACCOUNTSDetails">
    <link:loc xlink:type="locator" xlink:label="loc_srt_ValuationAndQualifyingAccountsDisclosureLineItems_bc281cfa-c761-468f-ae91-12bf146e89d1" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ValuationAndQualifyingAccountsDisclosureLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MovementInValuationAllowancesAndReservesRollForward_c142f7a2-fd3e-4e5e-8cfa-93c66d5280e3" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_MovementInValuationAllowancesAndReservesRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ValuationAndQualifyingAccountsDisclosureLineItems_bc281cfa-c761-468f-ae91-12bf146e89d1" xlink:to="loc_us-gaap_MovementInValuationAllowancesAndReservesRollForward_c142f7a2-fd3e-4e5e-8cfa-93c66d5280e3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationAllowancesAndReservesBalance_ff6ccc7d-3535-48b8-9cf5-788879034847" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ValuationAllowancesAndReservesBalance"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MovementInValuationAllowancesAndReservesRollForward_c142f7a2-fd3e-4e5e-8cfa-93c66d5280e3" xlink:to="loc_us-gaap_ValuationAllowancesAndReservesBalance_ff6ccc7d-3535-48b8-9cf5-788879034847" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationAllowancesAndReservesChargedToCostAndExpense_2b48c2e9-3176-4fea-9903-603212cd5718" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ValuationAllowancesAndReservesChargedToCostAndExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MovementInValuationAllowancesAndReservesRollForward_c142f7a2-fd3e-4e5e-8cfa-93c66d5280e3" xlink:to="loc_us-gaap_ValuationAllowancesAndReservesChargedToCostAndExpense_2b48c2e9-3176-4fea-9903-603212cd5718" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationAllowancesAndReservesChargedToOtherAccounts_fbe3e576-9e54-4923-b853-61551cb001f0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ValuationAllowancesAndReservesChargedToOtherAccounts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MovementInValuationAllowancesAndReservesRollForward_c142f7a2-fd3e-4e5e-8cfa-93c66d5280e3" xlink:to="loc_us-gaap_ValuationAllowancesAndReservesChargedToOtherAccounts_fbe3e576-9e54-4923-b853-61551cb001f0" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationAllowancesAndReservesDeductions_f8bc8db8-1fde-4272-b13d-cda3ca0e70c0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ValuationAllowancesAndReservesDeductions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MovementInValuationAllowancesAndReservesRollForward_c142f7a2-fd3e-4e5e-8cfa-93c66d5280e3" xlink:to="loc_us-gaap_ValuationAllowancesAndReservesDeductions_f8bc8db8-1fde-4272-b13d-cda3ca0e70c0" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationAllowancesAndReservesBalance_d7bc285a-8ba0-40e0-9198-580fc980d965" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ValuationAllowancesAndReservesBalance"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ValuationAndQualifyingAccountsDisclosureTable_85372de8-9eda-4c1f-8268-6f1a4df351f7" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ValuationAndQualifyingAccountsDisclosureTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_srt_ValuationAndQualifyingAccountsDisclosureLineItems_bc281cfa-c761-468f-ae91-12bf146e89d1" xlink:to="loc_srt_ValuationAndQualifyingAccountsDisclosureTable_85372de8-9eda-4c1f-8268-6f1a4df351f7" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationAllowancesAndReservesTypeAxis_ae5c7669-25d9-40d2-ba45-f3a84f77eafd" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ValuationAllowancesAndReservesTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_srt_ValuationAndQualifyingAccountsDisclosureTable_85372de8-9eda-4c1f-8268-6f1a4df351f7" xlink:to="loc_us-gaap_ValuationAllowancesAndReservesTypeAxis_ae5c7669-25d9-40d2-ba45-f3a84f77eafd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationAllowancesAndReservesDomain_ae5c7669-25d9-40d2-ba45-f3a84f77eafd_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ValuationAllowancesAndReservesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ValuationAllowancesAndReservesTypeAxis_ae5c7669-25d9-40d2-ba45-f3a84f77eafd" xlink:to="loc_us-gaap_ValuationAllowancesAndReservesDomain_ae5c7669-25d9-40d2-ba45-f3a84f77eafd_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationAllowancesAndReservesDomain_9c2c86fd-9679-42b8-b24c-a8b005a3e135" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ValuationAllowancesAndReservesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ValuationAllowancesAndReservesTypeAxis_ae5c7669-25d9-40d2-ba45-f3a84f77eafd" xlink:to="loc_us-gaap_ValuationAllowancesAndReservesDomain_9c2c86fd-9679-42b8-b24c-a8b005a3e135" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllowanceForCreditLossMember_f51c79de-08f5-49e9-b75d-c81ac817a174" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AllowanceForCreditLossMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ValuationAllowancesAndReservesDomain_9c2c86fd-9679-42b8-b24c-a8b005a3e135" xlink:to="loc_us-gaap_AllowanceForCreditLossMember_f51c79de-08f5-49e9-b75d-c81ac817a174" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationAllowanceOfDeferredTaxAssetsMember_c0021d16-5c8b-4fad-b581-1ee6decdbd0a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ValuationAllowanceOfDeferredTaxAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ValuationAllowancesAndReservesDomain_9c2c86fd-9679-42b8-b24c-a8b005a3e135" xlink:to="loc_us-gaap_ValuationAllowanceOfDeferredTaxAssetsMember_c0021d16-5c8b-4fad-b581-1ee6decdbd0a" xlink:type="arc" order="1"/>
  </link:definitionLink>
</link:linkbase>
