1

                        [NRG ENERGY, INC. LETTERHEAD]

 
 
                                               DAVID H. PETERSON
                                               Chairman, President and CEO
 
                                                                 October 9, 1998
 
Dear Fellow Stockholder:
 
     We need your help to reverse the disastrous slide in value of our common
investment in Cogeneration Corporation of America.
 
     NRG is the largest stockholder of COGEN and has seen the value of its
investment decline by approximately 60% in the past year. Reluctantly, we have
concluded that A CHANGE IN MANAGEMENT IS ESSENTIAL IF OUR INVESTMENT IS TO BE
SALVAGED.
 
     NRG is seeking to remove Robert Sherman from his position as a COGEN
director and as Chief Executive Officer. Following Mr. Sherman's removal, NRG's
nominees to the COGEN board are committed to seek the most qualified person
available to provide the kind of effective leadership COGEN needs.
 
     NRG put at risk over $100 million to enable COGEN to emerge from its
Chapter 11 bankruptcy proceeding and still holds approximately $28,000,000 of
COGEN common stock. NRG is committed to COGEN's success.
 
     Please read the enclosed proxy materials carefully and indicate your
approval of Mr. Sherman's removal on the enclosed proxy and consent cards and
return them in the enclosed envelopes as soon as possible.
 
                                          Very truly yours,
 

                                          /s/ DAVID H. PETERSON
                                          David H. Peterson