[TRIGEN ENERGY CORPORATION LETTERHEAD]

                                                     February 28, 2000

Dear Stockholder:

    On January 19, 2000,  Trigen Energy Corporation (the "Company"), Elyo
("Parent"), a societe anonyme organized and existing under the laws of the
Republic of France, and T Acquisition Corp. ("Purchaser"), a Delaware
corporation and an indirect wholly owned subsidiary of Parent, entered into a
merger agreement providing for the acquisition of any and all of the Common
Stock, par value $0.01 per share, of the Company at $23.50 cash per share.

    The Purchaser has today commenced a cash tender offer for any and all of
the issued and outstanding shares of Common Stock of the Company at a price
of $23.50 net per share.  The merger agreement provides that, following the
tender offer, Purchaser will merge with and into the Company and any
remaining shares of Common Stock of the Company will be converted into the
right to receive $23.50 per share in cash, without interest.

    At a meeting on January 19, 2000, your Board of Directors (the "Board")
by unanimous vote of all directors, based on, among other things, the
unanimous recommendation of a Special Committee comprised of independent
directors, (i) determined that the merger is advisable and that the terms of
the offer and the merger, the merger agreement and the consummation of the
transactions contemplated thereby are fair to, and in the best interests of,
the Company and its stockholders, (ii) approved the offer and the merger and
approved and adopted the merger agreement, and (iii) recommended the offer
to, and the approval and adoption of the merger agreement and the
transactions contemplated thereby by, the stockholders of the Company.

    In arriving at its recommendation, the Board gave careful consideration
to the factors described in the enclosed tender offer materials and Schedule
14D-9, including, among other things, the opinion of Credit Suisse First
Boston Corporation, the Special Committee's financial advisor, that as of
January 19, 2000, and based on and subject to the matters described in the
opinion, the price per share of $23.50 to be received in the offer and the
merger, taken together, by the holders of shares of Trigen common stock is
fair, from a financial point of view, to the holders of shares of Trigen
common stock, other than Elyo and its affiliates.

    Enclosed for your consideration are copies of the tender offer materials
and the Company's Schedule 14D-9, which are being filed today with the
Securities and Exchange Commission.  These documents should be read
carefully.

                                    Sincerely,

                                    ___________________________________
                                    Richard E. Kessel, President &
                                    Chief Executive Officer