UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, DC 20549

FORM 8-K/A

(Amendment No. 1)

CURRENT REPORT PURSUANT

TO SECTION 13 OR 15(D) OF THE

SECURITIES EXCHANGE ACT OF 1934

Date of report (Date of earliest event reported)  December 14, 2012

NRG Energy, Inc.

(Exact Name of Registrant as Specified in Its Charter)

Delaware

(State or Other Jurisdiction of Incorporation)

609-524-4500

(Registrant’s Telephone Number, Including Area Code)

Not Applicable

(Former Name or Former Address, if Changed Since Last Report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

o            Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

o            Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

o            Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

o            Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Introductory Note

As previously reported, on December 14, 2012, NRG Energy, Inc. (“NRG” or the “Company”) completed the previously announced merger contemplated by that certain Agreement and Plan of Merger, dated as of July 20, 2012, by and among NRG, GenOn Energy, Inc. (“GenOn”) and Plus Merger Corporation, a wholly-owned subsidiary of NRG. This Current Report on Form 8-K/A (the “Form 8-K/A”) amends the Current Report on Form 8-K filed by NRG with the Securities and Exchange Commission on December 14, 2012 to include the financial statements of GenOn and the pro forma financial information required by Items 9.01(a) and 9.01(b), respectively, and to include the exhibits under Item 9.01(d) of this Form 8-K/A.

Section 9 — Financial Statements and Exhibits

Item 9.01. Financial Statements and Exhibits.

(a)  Financial Statements of Businesses Acquired.

The audited consolidated financial statements of GenOn as of December 31, 2011 and 2010, and for each of the three years in the period ended December 31, 2011, and the unaudited consolidated financial statements of GenOn as of September 30, 2012 and for the three and nine months ended September 30, 2012 and 2011 are attached to this Form 8-K/A as Exhibit 99.1 and Exhibit 99.2, respectively, and are incorporated herein by reference.

(b)  Pro Forma Financial Information.

The unaudited pro forma condensed combined consolidated financial statements and explanatory notes relating to NRG’s acquisition of GenOn are attached as Exhibit 99.3 to this Form 8-K/A and are incorporated herein by reference.

(d)  Exhibits.

* * * * *

2

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

3

Exhibit 23.1

Consent of Independent Registered Public Accounting Firm

The Stockholder

GenOn Energy, Inc.:

We consent to the incorporation by reference in the registration statement (No. 333-185501) on Form S-8, (No. 333-182379) on Form S-8, (No. 333-171318) on Form S-8, (No. 333-151992) on Form S-8, (No. 333-135973) on Form S-8, (No. 333-114007) on Form S-8, (No. 333-123677) on Form S-3, (No. 333-183334) on Form S-4, (No. 333-178024) on Form S-4, (No. 333-175470) on Form S-4 and (No. 333-171323) on Form S-4 of NRG Energy, Inc. of our reports dated February 29, 2012, with respect to the consolidated balance sheets of GenOn Energy, Inc. and subsidiaries as of December 31, 2011 and 2010, and the related consolidated statements of operations, stockholders’ equity and comprehensive income (loss), cash flows, and the related financial statement schedules for each of the years in the three-year period ended December 31, 2011 and the effectiveness of internal control over financial reporting as of December 31, 2011, which reports appear in the Form 8-K/A of NRG Energy, Inc. dated March 1, 2013.

/s/ KPMG LLP

Houston, Texas

March 1, 2013

Exhibit 99.1

GenOn Energy, Inc.

Audited CONSOLIDATED Financial Statements

As of december 31, 2011 and 2010, and for each of the three years IN THE PERIOD ended december 31, 2011

Report of Independent Registered Public Accounting Firm

The Board of Directors and Stockholders

GenOn Energy, Inc.:

We have audited the accompanying consolidated balance sheets of GenOn Energy, Inc. and subsidiaries (the Company) as of December 31, 2011 and 2010, and the related consolidated statements of operations, stockholders’ equity and comprehensive income (loss), and cash flows for each of the years in the three-year period ended December 31, 2011. We also have audited the Company’s internal control over financial reporting at December 31, 2011, based on criteria established in Internal Control—Integrated Framework issued by the Committee of Sponsoring Organizations of the Treadway Commission (COSO). The Company’s management is responsible for these consolidated financial statements, for maintaining effective internal control over financial reporting, and for assessment of the effectiveness of internal control over financial reporting, included in Management’s Report on Internal Control over Financial Reporting within Item 9A. Our responsibility is to express an opinion on these consolidated financial statements and an opinion on the Company’s internal control over financial reporting based on our audits.

We conducted our audits in accordance with the standards of the Public Company Accounting Oversight Board (United States). Those standards require that we plan and perform the audits to obtain reasonable assurance about whether the financial statements are free of material misstatement and whether effective internal control over financial reporting was maintained in all material respects. Our audits of the consolidated financial statements included examining, on a test basis, evidence supporting the amounts and disclosures in the financial statements, assessing the accounting principles used and significant estimates made by management, and evaluating the overall financial statement presentation. Our audit of internal control over financial reporting included obtaining an understanding of internal control over financial reporting, assessing the risk that a material weakness exists, and testing and evaluating the design and operating effectiveness of internal control based on the assessed risk. Our audits also included performing such other procedures as we considered necessary in the circumstances. We believe that our audits provide a reasonable basis for our opinions.

A company’s internal control over financial reporting is a process designed to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles. A company’s internal control over financial reporting includes those policies and procedures that (1) pertain to the maintenance of records that, in reasonable detail, accurately and fairly reflect the transactions and dispositions of the assets of the company; (2) provide reasonable assurance that transactions are recorded as necessary to permit preparation of financial statements in accordance with generally accepted accounting principles, and that receipts and expenditures of the company are being made only in accordance with authorizations of management and directors of the company; and (3) provide reasonable assurance regarding prevention or timely detection of unauthorized acquisition, use, or disposition of the company’s assets that could have a material effect on the financial statements.

Because of its inherent limitations, internal control over financial reporting may not prevent or detect misstatements. Also, projections of any evaluation of effectiveness to future periods are subject to the risk that controls may become inadequate because of changes in conditions, or that the degree of compliance with the policies or procedures may deteriorate.

In our opinion, the consolidated financial statements referred to above present fairly, in all material respects, the financial position of GenOn Energy, Inc. and subsidiaries as of December 31, 2011 and 2010, and the results of their operations and their cash flows for each of the years in the three-year period ended December 31, 2011, in conformity with U.S. generally accepted accounting principles. Also in our opinion, the Company maintained, in all material respects, effective internal control over financial reporting as of December 31, 2011, based on criteria established in Internal Control—Integrated Framework issued by COSO.

/s/ KPMG LLP

Houston, Texas

February 29, 2012

F-1

GENON ENERGY, INC. AND SUBSIDIARIES

CONSOLIDATED STATEMENTS OF OPERATIONS

The accompanying notes are an integral part of these consolidated financial statements

F-2

GENON ENERGY, INC. AND SUBSIDIARIES

CONSOLIDATED BALANCE SHEETS

The accompanying notes are an integral part of these consolidated financial statements

F-3

GENON ENERGY, INC. AND SUBSIDIARIES

CONSOLIDATED STATEMENTS OF STOCKHOLDERS’ EQUITY

AND COMPREHENSIVE INCOME (LOSS)

The accompanying notes are an integral part of these consolidated financial statements

F-4

GENON ENERGY, INC. AND SUBSIDIARIES

CONSOLIDATED STATEMENTS OF CASH FLOWS

The accompanying notes are an integral part of these consolidated financial statements

F-5

GENON ENERGY, INC. AND SUBSIDIARIES

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS

December 31, 2011, 2010 and 2009

1. Description of Business and Accounting and Reporting Policies

Background

We are a wholesale generator with approximately 23,700 MW of net electric generating capacity located, in many cases, near major metropolitan load centers in the PJM, MISO, Northeast and Southeast regions, and California. We also operate integrated asset management and proprietary trading operations. See note 17 for a discussion of generating facilities in the Eastern PJM and Western PJM/MISO segments that we expect to deactivate between 2012 and 2015.

We were formed as a Delaware corporation in August 2000 by CenterPoint (then known as Reliant Energy, Incorporated) in connection with the planned separation of its regulated and unregulated operations. CenterPoint transferred substantially all of its unregulated businesses, including the name Reliant Energy, to the company now named GenOn Energy, Inc. In May 2001, Reliant Energy (then known as Reliant Resources, Inc.) became a publicly traded company and in September 2002, CenterPoint distributed its remaining ownership of Reliant Energy’s common stock to its stockholders. RRI Energy changed its name from Reliant Energy, Inc. effective May 2, 2009 in connection with the sale of its retail business. GenOn changed its name from RRI Energy, Inc. effective December 3, 2010 in connection with the Merger. “We,” “us,” “our” and “GenOn” refer to GenOn Energy, Inc. and, except where the context indicates otherwise, its subsidiaries, after giving effect to the Merger.

Merger of Mirant and RRI Energy

On December 3, 2010, Mirant and RRI Energy completed the Merger. Upon completion of the Merger, RRI Energy Holdings, Inc., a direct and wholly- owned subsidiary of RRI Energy merged with and into Mirant, with Mirant continuing as the surviving corporation and a wholly-owned subsidiary of RRI Energy. Each of Mirant and RRI Energy received legal opinions that the Merger qualified as a tax-free reorganization under the IRC. Upon the closing of the Merger, each issued and outstanding share of Mirant common stock, including grants of restricted common stock, automatically converted into 2.835 shares of common stock of RRI Energy based on the Exchange Ratio. Approximately 417 million shares of RRI Energy common stock were issued. Additionally, upon the closing of the Merger, RRI Energy was renamed GenOn. Mirant stock options and other equity awards converted upon completion of the Merger into stock options and equity awards with respect to GenOn common stock, after giving effect to the Exchange Ratio. See note 2 for additional information on the Merger and note 6 for the related debt transactions.

During the third and fourth quarters of 2011, we recorded revisions to the provisional allocation of the purchase price at December 3, 2010 and accordingly retroactively revised amounts in our consolidated balance sheet at December 31, 2010 and our consolidated statements of operations for 2010 and the nine months ended September 30, 2011. See note 2.

Basis of Presentation

The consolidated financial statements of GenOn and its wholly-owned subsidiaries have been prepared in accordance with GAAP from records maintained by us. All significant intercompany accounts and transactions have been eliminated in consolidation.

In connection with the Merger, former Mirant stockholders received approximately 54% of the voting interest in the combined company. Although RRI Energy was the legal acquirer, the Merger is

F-6

GENON ENERGY, INC. AND SUBSIDIARIES

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (Continued)

December 31, 2011, 2010 and 2009

1. Description of Business and Accounting and Reporting Policies (Continued)

accounted for as a reverse acquisition whereby Mirant is treated as the accounting acquirer and RRI Energy is treated as the acquired company for financial reporting purposes. As such, our consolidated financial statements include the results of the combined entities for the periods from December 3, 2010, and include the results of Mirant through December 2, 2010. Our consolidated results of operations in 2010 include operating revenues from RRI Energy of $168 million and a net loss of $60 million after the Merger. The consolidated financial statements presented herein for periods ended prior to the closing of the Merger (and any other financial information presented herein with respect to such pre-merger dates, unless otherwise specified) are the consolidated financial statements and other financial information of Mirant.

At December 31, 2011 and 2010, substantially all of our subsidiaries are wholly-owned and located in the United States. We did not consolidate five power generating facilities, which are under operating leases (see note 10); a 50% equity investment in a cogeneration facility; and a VIE, for which we are not the primary beneficiary (see note 13 for further discussion of MC Asset Recovery).

Use of Estimates

The preparation of consolidated financial statements in conformity with GAAP requires management to make various estimates and assumptions that affect the reported amounts of assets and liabilities, disclosures of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenues and expenses during the period. Actual results could differ from those estimates. Our significant estimates include:

·                  estimating the fair value of assets acquired and liabilities assumed in connection with the Merger;

·                  estimating the fair value of certain derivative contracts;

·                  estimating future taxable income in evaluating the deferred tax asset valuation allowance;

·                  estimating the useful lives of long-lived assets;

·                  estimating future costs and the valuation of asset retirement obligations;

·                  estimating future cash flows in determining impairments of long-lived assets and definite-lived intangible assets;

·                  estimating the fair value and expected return on plan assets, discount rates and other actuarial assumptions used in estimating pension and other postretirement benefit plan liabilities; and

·                  estimating losses to be recorded for contingent liabilities.

We evaluate events that occur after the balance sheet date and through the date the financial statements are issued for potential recognition or disclosure. Based on the evaluation, we determined that there were no material subsequent events for recognition or disclosure other than those disclosed herein.

F-7

GENON ENERGY, INC. AND SUBSIDIARIES

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (Continued)

December 31, 2011, 2010 and 2009

1. Description of Business and Accounting and Reporting Policies (Continued)

Revenue Recognition

We recognize revenue when earned and collection is probable. We earn revenue from the following sources: (a) power generation revenues, (b) contracted and capacity revenues, (c) fuel sales and proprietary trading revenues and (d) power hedging revenues.

Power Generation Revenues.  We recognize revenue from the sale of electricity from our generating facilities. Sales of energy primarily are based on economic dispatch, or “as-ordered” by an ISO or RTO, based on member participation agreements, but without an underlying contractual commitment. ISO and RTO revenues and revenues from sales of energy based on economic-dispatch are recorded on the basis of MWh delivered, at the relevant day-ahead or real-time prices. Additionally, we include revenue from the sale of steam in power generation revenues.

Contracted and Capacity Revenues.  We recognize revenue received from providing ancillary services and revenue received from an ISO or RTO based on auction results or negotiated contract prices for making installed generation capacity available to meet system reliability requirements. In addition, when a long-term electric power agreement conveys to the buyer of the electric power the right to control the generating capacity of our facility, that agreement is evaluated to determine if it is a lease of the generating facility rather than a sale of electric power. Operating lease revenue for our generating facilities is normally recorded as capacity revenue.

Power Hedging Revenues.  We recognize revenue from contracts for the sale of both power and natural gas used to hedge power prices as well as for hedges to capture the incremental value related to the geographic location of our physical assets.

Fuel Sales and Proprietary Trading Revenues.  We recognize revenue from the sale of fuel oil and natural gas and revenues associated with fuel oil management and proprietary trading activities.

The following table reflects our revenues by type:

In accordance with accounting guidance related to derivative financial instruments, physical transactions or revenues from the sale of generated electricity to ISOs and RTOs are recorded on a gross basis in the consolidated statements of operations. Financial transactions, or the buying and selling of energy for trading purposes, are recorded on a net basis in the consolidated statements of operations.

F-8

GENON ENERGY, INC. AND SUBSIDIARIES

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (Continued)

December 31, 2011, 2010 and 2009

1. Description of Business and Accounting and Reporting Policies (Continued)

Cost of Fuel, Electricity and Other Products

Cost of fuel, electricity and other products on our consolidated statements of operations includes the costs of goods produced and sold through the combustion process, including the costs associated with handling and disposal of ash, natural gas transportation and services rendered during a reporting period. Cost of fuel, electricity and other products also includes purchased emissions allowances for CO2, SO2 and NOx and the settlements of and changes in fair value of derivative financial instruments used to hedge fuel economically. Additionally, cost of fuel, electricity and other products includes lower of cost or market inventory adjustments. Cost of fuel, electricity and other products excludes depreciation and amortization. Gross margin is total operating revenues less cost of fuel, electricity and other products.

Derivatives and Hedging Activities

In connection with the business of generating electricity, we are exposed to energy commodity price risk associated with the acquisition of fuel and emissions allowances needed to generate electricity, the price of electricity produced and sold, and the fair value of fuel inventories. Through our asset management activities, we enter into a variety of exchange-traded and OTC energy and energy-related derivative financial instruments, such as forward contracts, futures contracts, option contracts and financial swap agreements to manage exposure to commodity price risks. These contracts have varying terms and durations, which range from a few days to years, depending on the instrument. Our proprietary trading activities also utilize similar derivative contracts in markets where we have a physical presence to attempt to generate incremental gross margin. Our fuel oil management activities use derivative financial instruments to hedge economically the fair value of physical fuel oil inventories, optimize the approximately two million barrels of storage capacity that we own, and attempt to profit from market opportunities related to timing and/or differences in the pricing of various products. The open positions in our trading activities comprising proprietary trading and fuel oil management activities expose us to risks associated with changes in energy commodity prices.

Derivative financial instruments are recorded in the consolidated balance sheets at fair value, except for derivative contracts that qualify for and for which we have elected the normal purchase or normal sale exceptions, which are not reflected in the consolidated balance sheet or results of operations prior to accrual of the settlement. We present our derivative contract assets and liabilities on a gross basis (regardless of master netting arrangements with the same counterparty). Cash collateral amounts are also presented on a gross basis.

If certain criteria are met, a derivative financial instrument may be designated as a fair value hedge or cash flow hedge. In the fourth quarter of 2010, GenOn Marsh Landing entered into interest rate protection agreements (interest rate swaps) in connection with its project financing, which have been designated as cash flow hedges. GenOn Marsh Landing entered into the interest rate swaps to reduce the risks with respect to the variability of the interest rates for the term loans. With the exception of these interest rate swaps, we did not have any other derivative financial instruments designated as fair value or cash flow hedges for accounting purposes during 2011, 2010, or 2009.

The changes in fair value of cash flow hedges are deferred in accumulated other comprehensive loss, net of tax, to the extent the contracts are, or have been, effective as hedges, until the forecasted

F-9

GENON ENERGY, INC. AND SUBSIDIARIES

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (Continued)

December 31, 2011, 2010 and 2009

1. Description of Business and Accounting and Reporting Policies (Continued)

transactions affect earnings. We record the ineffective portion of changes in fair value of cash flow hedges immediately into earnings.

Derivative financial instruments designated as cash flow hedges must have a high correlation between price movements in the derivative and the hedged item. If and when an acceptable level of correlation no longer exists, hedge accounting ceases and changes in fair value are recognized in our results of operations. If it becomes probable that a forecasted transaction will not occur, we immediately recognize the related deferred gains or losses in our results of operations. Changes in fair value of the associated hedging instrument are then recognized immediately in earnings for the remainder of the contract term unless a new hedging relationship is designated.

For our derivative financial instruments that have not been designated as cash flow hedges for accounting purposes, changes in such instruments’ fair values are recognized currently in earnings. Our derivative financial instruments are categorized based on the business objective the instrument is expected to achieve: asset management or trading, which includes proprietary trading and fuel oil management. For asset management activities, changes in fair value and settlement of derivative financial instruments used to hedge electricity economically are reflected in operating revenues and changes in fair value and settlement of derivative financial instruments used to hedge fuel economically are reflected in cost of fuel, electricity and other products in the consolidated statements of operations. Changes in the fair value and settlements of derivative financial instruments for proprietary trading and fuel oil management activities are recorded on a net basis as operating revenue in the consolidated statements of operations.

We also consider risks associated with interest rates, counterparty credit and our own non-performance risk when valuing derivative financial instruments. The nominal value of the derivative contract assets and liabilities is discounted to account for time value using a LIBOR forward interest rate curve based on the tenor of the transactions being valued. See note 4.

Concentration of Revenues

During 2011, we had $2.3 billion in revenues from PJM, which represented 62% of consolidated revenues. The revenues generated from this counterparty are included in the Eastern PJM, Western PJM/MISO and Energy Marketing segments. During 2010, we had $1.5 billion in revenues from PJM, which represented 64% of consolidated revenues. The revenues generated from this counterparty are included in the Eastern PJM, Western PJM/MISO and Energy Marketing segments. During 2009, we had $1.0 billion in revenues from PJM, which represented 43% of consolidated revenues. The revenues generated from this counterparty are primarily included in the Eastern PJM segment. Additionally, during 2009 we had $332 million in revenues from another counterparty, which represented 14% of consolidated revenues. The revenues generated from this counterparty are included in the Eastern PJM, Energy Marketing and Other Operations segments.

Coal Supplier Concentration Risk

Our coal supply comes primarily from the Northern Appalachian and Central Appalachian coal regions. We enter into contracts of varying tenors to secure appropriate quantities of fuel that meet the varying specifications of our generating facilities. For the coal-fired generating facilities, we purchase

F-10

GENON ENERGY, INC. AND SUBSIDIARIES

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (Continued)

December 31, 2011, 2010 and 2009

1. Description of Business and Accounting and Reporting Policies (Continued)

most of our coal from a small number of suppliers under contracts with terms of varying lengths, some of which extend to 2014 and one that extends to 2020. Excluding the Keystone and Conemaugh generating facilities (which are not 100% owned by us) and excluding the Seward generating facility (which burns waste coal supplied by an all-requirements contract), we had exposure to three counterparties at December 31, 2011 and 2010, that each represented an exposure of more than 10% of our total coal commitments, by volume, and in aggregate represented approximately 62% and 76% of our total coal commitments at December 31, 2011 and 2010, respectively. At December 31, 2011 and 2010, the single largest counterparty represented an exposure of 38% and 52%, respectively, of these total coal commitments, by volume.

Coal Transportation Concentration Risk

The coal to operate our coal-fired facilities is delivered primarily by train and we have a limited number of railroads transporting such coal. For 2011, one railroad represented 66% of our coal transportation costs and another railroad represented 22% of our coal transportation costs.

Concentration of Labor Subject to Collective Bargaining Agreements

At December 31, 2011, 50% of our employees are subject to collective bargaining agreements. Of those employees subject to collective bargaining agreements, 33% are represented by IBEW Local 459 in the Western PJM/MISO segment and 30% are represented by IBEW Local 1900 in the Eastern PJM segment. Less than five percent of our employees are subject to a collective bargaining agreement that will expire in 2012. We intend to negotiate the renewal of this agreement and do not anticipate any disruptions to our operations.

Cash and Cash Equivalents

We consider all short-term investments with an original maturity of three months or less to be cash equivalents. At December 31, 2011 and 2010, except for amounts held in bank accounts to cover current payables, all of our cash and cash equivalents were invested in AAA-rated United States Treasury money market funds.

F-11

GENON ENERGY, INC. AND SUBSIDIARIES

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (Continued)

December 31, 2011, 2010 and 2009

1. Description of Business and Accounting and Reporting Policies (Continued)

Funds on Deposit

Funds on deposit are included in current and noncurrent assets in the consolidated balance sheets. Funds on deposit include the following:

(1)                                 Includes $32 million related to the Potomac River settlement. See note 5.

(2)                                 Represents cash under surety bonds posted primarily with the Pennsylvania Department of Environmental Protection related to environmental obligations.

(3)                                 Represents cash reserved in respect of interlocutory liens related to the scrubber contract litigation. See note 16.

(4)                                 Represents cash-collateralized letters of credit to support the Marsh Landing development project.

(5)                                 Represents deposits with the State of Pennsylvania to guarantee our obligations related to future closures of coal ash landfill sites and with the State of New Jersey to satisfy our obligations under the Industrial Site Recovery Act. See note 16 for our obligations related to ash landfill sites and site contamination remediation.

(6)                                 See note 6 for discussion of the related debt.

Inventories

Inventories consist primarily of materials and supplies, fuel oil, coal and purchased emissions allowances. Inventory is generally stated at the lower of cost or market value and is expensed on a weighted average cost basis. Fuel inventory is removed from the inventory account as it is used in the

F-12

GENON ENERGY, INC. AND SUBSIDIARIES

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (Continued)

December 31, 2011, 2010 and 2009

1. Description of Business and Accounting and Reporting Policies (Continued)

generation of electricity or sold to third parties, including sales related to our fuel oil management, natural gas transportation and storage activities. Materials and supplies are removed from the inventory account when they are used for repairs, maintenance or capital projects. Purchased emissions allowances are removed from inventory and charged to cost of fuel, electricity and other products in the consolidated statements of operations as they are utilized for emissions volumes.

Inventories were comprised of the following:

During 2011, 2010 and 2009, we recorded $13 million, $22 million and $32 million, respectively, for lower of average cost or market valuation adjustments in cost of fuel, electricity and other products.

Property, Plant and Equipment

Property, plant and equipment are recorded at cost, which includes materials, labor, associated payroll-related and overhead costs and the cost of financing construction. The cost of routine maintenance and repairs, such as inspections and corrosion removal, and the replacement of minor items of property are charged to expense as incurred. Certain expenditures incurred during a major maintenance outage of a generating facility are capitalized, including the replacement of major component parts and labor and overhead incurred to install the parts. Depreciation of the recorded cost of depreciable property, plant and equipment is determined using primarily composite rates. Leasehold improvements are depreciated over the shorter of the expected life of the related equipment or the lease term. Upon the retirement or sale of property, plant and equipment, the cost of such assets and the related accumulated depreciation are removed from the consolidated balance sheets. No gain or loss is recognized for ordinary retirements in the normal course of business since the composite depreciation rates used by us take into account the effect of interim retirements.

Impairment of Long-Lived Assets

We evaluate long-lived assets, such as property, plant and equipment and purchased intangible assets subject to amortization, for impairment whenever events or changes in circumstances indicate that the carrying amount of the asset may not be recoverable. Such evaluations are performed in accordance with the accounting guidance related to evaluating long-lived assets for impairment. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset to the estimated undiscounted future net cash flows expected to be generated by the asset. If the carrying amount of an

F-13

GENON ENERGY, INC. AND SUBSIDIARIES

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (Continued)

December 31, 2011, 2010 and 2009

1. Description of Business and Accounting and Reporting Policies (Continued)

asset exceeds its estimated undiscounted future net cash flows, an impairment charge is recognized as the amount by which the carrying amount of the asset exceeds its fair value. See note 5.

Capitalization of Interest Cost

We capitalize interest on projects during their construction period. We determine which debt instruments represent a reasonable measure of the cost of financing construction in terms of interest costs incurred that otherwise could have been avoided. These debt instruments and associated interest costs are included in the calculation of the weighted average interest rate used for determining the capitalization rate. Once a project is placed in service, capitalized interest, as a component of the total cost of the construction, is depreciated over the estimated useful life of the asset constructed.

During 2011, 2010 and 2009, we incurred the following interest costs:

The amounts of capitalized interest above include interest accrued. During 2011, 2010 and 2009, cash paid for interest was $396 million, $250 million and $192 million, respectively, of which $14 million, $6 million and $68 million, respectively, were capitalized.

Environmental Costs

We expense environmental expenditures related to existing conditions that do not have future economic benefit. We capitalize environmental expenditures for which there is a future economic benefit. We record liabilities for expected future costs, on an undiscounted basis, related to environmental assessments and/or remediation when they are probable and can be reasonably estimated. In determining the liabilities, we refer to currently available information, including relevant past experience, remedial objectives, available technologies and applicable laws and regulations. We record reimbursements or recoveries of environmental remediation costs in income when received, or when receipt of recovery is highly probable.

Development Costs

We capitalize project development costs for generating facilities once it is probable that the project will be completed. These costs include professional fees, permits and other third party costs directly associated with the development of a new project. The capitalized costs are depreciated over the life of the asset or charged to operating expense if the completion of the project is deemed no longer probable. Project development costs are expensed when incurred until the probable threshold is met. We began capitalizing project development costs related to the Marsh Landing generating facility upon signing the PPA with PG&E on September 2, 2009. At December 31, 2011 and 2010, we have

F-14

GENON ENERGY, INC. AND SUBSIDIARIES

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (Continued)

December 31, 2011, 2010 and 2009

1. Description of Business and Accounting and Reporting Policies (Continued)

capitalized $8 million and $5 million, respectively, of project development costs related to the Marsh Landing generating facility.

Operating Leases

We lease various assets under non-cancelable leasing arrangements, including generating facilities, office space and other equipment. The rent expense associated with leases that qualify as operating leases is recognized on a straight-line basis over the lease term within operations and maintenance expense in the consolidated statements of operations. Our most significant operating leases are GenOn Mid-Atlantic’s leases of a 100% interest in the Dickerson and Morgantown baseload units and REMA’s leases of a 16.45% interest in the Conemaugh facility, a 16.67% interest in the Keystone facility and a 100% interest in the Shawville facility. See note 10.

Intangible Assets

Intangible assets relate primarily to acquired contracts, granted emissions allowances, trading rights and development rights. Intangible assets with definite useful lives are amortized on a straight-line basis to their estimated residual values over their respective useful lives ranging up to 30 years. See note 5.

Debt Issuance Costs

Debt issuance costs are capitalized and amortized as interest expense under the effective interest method over the term of the related debt. The unamortized balance of debt issuance costs is included in other noncurrent assets on the consolidated balance sheets. Changes in debt issuance costs are as follows:

(1)                                 See note 6.

(2)                                 Amounts are considered a portion of the net carrying value of the related debt and are expensed when accelerated as a component of debt extinguishments.

Income Taxes and Deferred Tax Asset Valuation Allowance

Income taxes are accounted for under the asset and liability method. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases and operating loss and tax credit carryforwards. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period that includes the enactment date.

F-15

GENON ENERGY, INC. AND SUBSIDIARIES

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (Continued)

December 31, 2011, 2010 and 2009

1. Description of Business and Accounting and Reporting Policies (Continued)

The guidance related to accounting for income taxes requires that a valuation allowance be established when it is more-likely-than-not that all or a portion of a deferred tax asset will not be realized. The ultimate realization of deferred tax assets is dependent upon the generation of future taxable income of the appropriate character during the periods in which those temporary differences are deductible. In making this determination, management considers all available positive and negative evidence affecting specific deferred tax assets, including our past and anticipated future performance, the reversal of deferred tax liabilities and the implementation of tax planning strategies.

At December 31, 2011, our deferred tax assets reduced by a valuation allowance are completely offset by our deferred tax liabilities. Objective positive evidence is necessary to support a conclusion that a valuation allowance is not needed for all or a portion of deferred tax assets when significant negative evidence exists. We think that future sources of taxable income, the reversal of taxable temporary differences and implemented tax planning strategies will be sufficient to realize deferred tax assets for which no valuation allowance has been established.

Earnings per Share

Basic earnings per share is calculated by dividing net income/loss applicable to common stockholders by the weighted average number of common shares outstanding. Diluted earnings per share is computed using the weighted average number of shares of common stock and dilutive potential common shares, including common shares from warrants, restricted stock units and stock options using the treasury stock method. Share amounts used in calculating earnings per share reflect Mirant’s historical activity through December 2, 2010 retroactively adjusted to give effect to the Exchange Ratio and includes the combined entities for the periods from December 3, 2010.

Fair Value of Financial Instruments

The accounting guidance related to the disclosure about fair value of financial instruments requires the disclosure of the fair value of all financial instruments that are not otherwise recorded at fair value in the financial statements. At December 31, 2011 and 2010, financial instruments recorded at contractual amounts that approximate fair value include certain funds on deposit, accounts receivable, notes and other receivables, and accounts payable and accrued liabilities. The fair values of such items are not materially sensitive to shifts in market interest rates because of the short term to maturity of these instruments. See note 4.

Recently Adopted Accounting Guidance

Fair Value Measurement and Disclosure.  We adopted FASB accounting guidance for the quarter ended March 31, 2011 that requires a reconciliation for Level 3 fair value measurements, including presenting separately the amounts of purchases, issuances and settlements on a gross basis. See note 4.

New Accounting Guidance Not Yet Adopted at December 31, 2011

Fair Value Measurement and Disclosure.  In May 2011, the FASB issued new fair value measurement and disclosure guidance. The new standard does not extend the use of fair value but rather provides guidance about how fair value should be determined and requires additional

F-16

GENON ENERGY, INC. AND SUBSIDIARIES

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (Continued)

December 31, 2011, 2010 and 2009

1. Description of Business and Accounting and Reporting Policies (Continued)

disclosures. The guidance is not expected to have a material effect on our fair value measurements, but will require disclosure of the following:

·                  quantitative information about the unobservable inputs used in a fair value measurement that is categorized within Level 3 of the fair value hierarchy;

·                  for those fair value measurements categorized within Level 3 of the fair value hierarchy, both the valuation processes used and the sensitivity of the fair value measurement to changes in unobservable inputs and the interrelationships between those unobservable inputs, if any; and

·                  the categorization by level of the fair value hierarchy for items that are not measured at fair value in the statement of financial position but for which the fair value is required to be disclosed.

We will present the additional disclosures as required in our Form 10-Q for the quarter ended March 31, 2012.

Comprehensive Income.  In June 2011, the FASB issued guidance that revises the manner in which companies present comprehensive income in their financial statements. The guidance requires companies to report the components of comprehensive income in either (a) a continuous statement of comprehensive income or (b) two separate but consecutive statements. The guidance does not change the items that must be reported in comprehensive income. We will update our presentation as required in our Form 10-Q for the quarter ended March 31, 2012.

Balance Sheet Offsetting.  In December 2011, the FASB issued updated guidance to provide enhanced disclosures such that users of the financial statements will be able to better evaluate the effect or potential effect of netting arrangements on the statement of financial position. The guidance requires improved information about financial instruments and derivative instruments that are either offset according to specific guidance or subject to an enforceable master netting agreement or similar arrangement. The disclosures will provide both net and gross information for these assets and liabilities. Although we do not currently elect to offset assets and liabilities within the scope of the guidance, expanded disclosures will be required starting for the quarter ended March 31, 2013, along with retrospective presentation of prior periods.

2. Merger

On December 3, 2010, Mirant and RRI Energy completed the Merger. The Merger resulted in significant cost savings, a generation fleet with diversity and a significant presence in PJM and California, and a balance sheet with adequate liquidity.

Because the Merger is accounted for as a reverse acquisition with Mirant as the accounting acquirer (see note 1, “Basis of Presentation” section), the purchase price was computed based on shares of Mirant common stock that would have been issued to RRI Energy’s stockholders on the date of the Merger to give RRI Energy an equivalent ownership interest in Mirant as it had in the

F-17

GENON ENERGY, INC. AND SUBSIDIARIES

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (Continued)

December 31, 2011, 2010 and 2009

2. Merger (Continued)

combined company (approximately 46%). The purchase price was calculated as follows (in millions, except closing stock price):

The Merger is accounted for under the acquisition method of accounting for business combinations. Accordingly, we have conducted an assessment of the net assets acquired and recognized amounts for identifiable assets acquired and liabilities assumed at their estimated acquisition date fair values, while transaction and integration costs associated with the acquisition are expensed as incurred. We finalized our assessment of fair value during 2011, and adjusted for information that was previously not available to us. The final allocation of the purchase price as of December 3, 2010 is as follows (in millions):

(1)         The valuations of the acquired long-lived assets were primarily based on the income approach, and in particular, discounted cash flow analyses. The income approach was employed for the generating facilities because of the differing age, geographic location, market conditions, asset life, equipment condition and status of environmental controls of the assets. The discounted cash flows incorporated information based on observable market prices to the extent available and long-term prices derived from proprietary fundamental market modeling. For the generating facilities that were not valued using the income approach, the cost approach was used. The market approach was considered, but

F-18

GENON ENERGY, INC. AND SUBSIDIARIES

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (Continued)

December 31, 2011, 2010 and 2009

2. Merger (Continued)

was ultimately given no weighting because of many of the factors listed as the primary reasons for application of the income approach as well as a lack of proximity of the observed transactions to the valuation date.

(2)         The gain on bargain purchase was recorded in other income in the consolidated statement of operations during 2010.

(3)         The acquisition is treated as a nontaxable merger for federal income tax purposes and there is no tax deductible goodwill resulting from the Merger.

The above allocation of the purchase price includes revisions to the provisional allocation that was reported at September 30, 2011, June 30, 2011, March 31, 2011 and December 31, 2010 primarily for property, plant and equipment, intangible assets and long-term liabilities related to out-of-market contracts and asset retirement obligations, which reduced the gain on bargain purchase recognized during 2010 by $183 million. Our consolidated balance sheet at December 31, 2010 has been retroactively amended for the revisions to the provisional allocation as follows:

Our results of operations have been retroactively amended for the revisions to the provisional allocation as follows: (a) for the nine months ended September 30, 2011, our net loss increased by $7 million and (b) for the year ended December 31, 2010, the gain on bargain purchase decreased by $183 million and the net loss increased by the same amount. The impacts on our results of operations for 2010, other than the gain on bargain purchase, as a result of the revisions to the provisional allocation were not material.

F-19

GENON ENERGY, INC. AND SUBSIDIARIES

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (Continued)

December 31, 2011, 2010 and 2009

2. Merger (Continued)

Because the fair value of the net assets acquired exceeds the purchase price, the Merger is being accounted for as a bargain purchase in accordance with acquisition accounting guidance. The gain on the bargain purchase is primarily a result of differences between the long-term fundamental value of the generating facilities and the effect of the near-term view of the equity markets on the price of Mirant common stock at the close of the Merger, specifically as a result of the following:

·                  dark spreads (the difference between power prices and coal fuel costs) have decreased significantly in recent years as a result of natural gas prices that are lower compared to recent years and increased coal prices that are affected by international demand;

·                  uncertainty related to the nature and timing of environmental regulation, including carbon legislation; and

·                  certain generating facilities owned by RRI Energy prior to the Merger being located in markets experiencing lower demand for electricity as a result of economic conditions but forecasted to have long-term declining reserve margins.

We are subject to material contingencies, some of which may involve substantial amounts, relating to (a) pending natural gas litigation, (b) environmental matters, (c) the CenterPoint indemnity, (d) the Texas franchise tax audit and (e) income tax contingencies. For information regarding these contingencies, see notes 7 and 16. As a result of the number of variables and assumptions involved in assessing the possible outcome of these matters, sufficient information does not exist to reasonably estimate the fair value or a range of outcomes for these contingent liabilities, except as disclosed in notes 7 and 16. Unless otherwise noted in notes 7 and 16, we cannot predict the outcome of the matters. These material contingencies have been evaluated in accordance with the accounting guidance for contingencies, and no amounts for these matters have been recorded at the date of the Merger because the recognition criteria have not been met, except as denoted in notes 7 and 16. See note 10 for information regarding guarantees and indemnifications.

In connection with the Merger, we incurred stock issuance costs of an insignificant amount, which were recorded as an increase in additional paid-in capital in stockholders’ equity as of the date of the Merger and incurred debt issuance costs of $68 million, which are included in other noncurrent assets in the consolidated balance sheet. For information regarding debt issuance costs, see note 1. For information regarding Merger-related costs, see note 3.

The unaudited pro forma results give effect to the Merger as if it had occurred on January 1, 2010 and 2009, as applicable. The unaudited pro forma financial information is not necessarily indicative of either future results of operations or results that might have been achieved had the acquisition been

F-20

GENON ENERGY, INC. AND SUBSIDIARIES

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (Continued)

December 31, 2011, 2010 and 2009

2. Merger (Continued)

consummated as of January 1, 2010 or January 1, 2009, as applicable. The unaudited pro forma results for 2010 and 2009 are as follows:

The unaudited pro forma information primarily includes the following adjustments, among others:

·                  amortization of fair value adjustments related to energy-related contracts;

·                  additional fuel expense related to fair value adjustments of fuel inventories;

·                  effects of fair value adjustments of property, plant and equipment;

·                  effects of fair value adjustments of debt and the issuance of a new revolving credit facility, new senior secured term loan and new senior unsecured notes; and

·                  adjustments to income taxes for a zero percent rate applied to the pro forma adjustments and historical federal and state deferred tax expense (benefit).

The unaudited pro-forma results exclude:

·                  transaction costs of $86 million (including amounts incurred prior to the close of the Merger) because these costs reflect non-recurring charges directly related to the Merger;

·                  $35 million of severance related to the Merger (see note 3) and $18 million of other Merger-related costs;

·                  write-off of $9 million of unamortized debt issuance costs for the debt refinanced, cash premiums and other transaction costs of the debt refinanced;

·                  $24 million of expense related to the accelerated vesting of stock-based compensation of former Mirant employees upon the completion of the Merger;

·                  the gain on bargain purchase; and

·                  cost savings from operating efficiencies or synergies that could result from the Merger.

F-21

GENON ENERGY, INC. AND SUBSIDIARIES

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (Continued)

December 31, 2011, 2010 and 2009