OFFER TO PURCHASE FOR CASH ANY AND ALL OUTSTANDING SHARES OF COMMON STOCK OF TRIGEN ENERGY CORPORATION AT $23.50 NET PER SHARE BY T ACQUISITION CORP. AN INDIRECT WHOLLY OWNED SUBSIDIARY OF ELYO AN INDIRECT WHOLLY OWNED SUBSIDIARY OF SUEZ LYONNAISE DES EAUX THE OFFER AND WITHDRAWAL RIGHTS WILL EXPIRE AT 12:00 MIDNIGHT, NEW YORK CITY TIME, ON FRIDAY, MARCH 24, 2000, UNLESS THE OFFER IS EXTENDED. To Brokers, Dealers, Commercial Banks, Trust Companies and Other Nominees: February 28, 2000 We are writing to you in connection with the offer by T Acquisition Corp., a Delaware corporation ("Purchaser") and an indirect wholly owned subsidiary of Elyo, a SOCIETE ANONYME organized and existing under the laws of the Republic of France ("Parent") and an indirect wholly owned subsidiary of Suez Lyonnaise des Eaux, a SOCIETE ANONYME organized and existing under the laws of the Republic of France ("Suez Lyonnaise"), to purchase any and all outstanding shares of Common Stock, par value $0.01 per share (the "Shares"), of Trigen Energy Corporation, a Delaware corporation (the "Company"), at a price of $23.50 per Share, net to the seller in cash, without interest thereon, upon the terms and subject to the conditions set forth in the Offer to Purchase, dated February 28, 2000 (the "Offer to Purchase"), and in the related Letter of Transmittal (which, together with any amendments or supplements thereto, collectively constitute the "Offer") enclosed herewith. The Offer is being made in connection with the Agreement and Plan of Merger, dated as of January 19, 2000 (the "Merger Agreement"), among Parent, Purchaser and the Company. Holders of Shares whose certificates for such Shares (the "Certificates") are not immediately available or who cannot deliver their Certificates and all other required documents to Harris Trust Company of New York (the "Depositary") or complete the procedures for book-entry transfer prior to the Expiration Date (as defined under "THE TENDER OFFER--Terms of the Offer" of the Offer to Purchase) must tender their Shares according to the guaranteed delivery procedures set forth under "THE TENDER OFFER--Procedures for Tendering Shares" of the Offer to Purchase. Please furnish copies of the enclosed materials to those of your clients for whose accounts you hold Shares in your name or in the name of your nominee. Enclosed herewith for your information and for forwarding to your clients are copies of the following documents: 1. The Offer to Purchase, dated February 28, 2000. 2. The Letter of Transmittal to tender Shares for your use and for the information of your clients. Facsimile copies of the Letter of Transmittal may be used to tender Shares. 3. A letter to stockholders of the Company from Richard E. Kessel, President and Chief Executive Officer of the Company, together with a Solicitation/Recommendation Statement on Schedule 14D-9 filed by the Company with the Securities and Exchange Commission and mailed to the stockholders of the Company. 4. The Notice of Guaranteed Delivery for Tender of Shares to be used to accept the Offer if the guaranteed delivery procedures set forth under "THE TENDER OFFER--Procedures for Tendering Shares" of the Offer to Purchase are to be followed. 5. A printed form of a letter which may be sent to your clients for whose accounts you hold Shares registered in your name, with space provided for obtaining such clients' instructions with regard to the Offer. 6. Guidelines of the Internal Revenue Service for Certification of Taxpayer Identification Number on Substitute Form W-9. 7. A return envelope addressed to the Depositary. YOUR PROMPT ACTION IS REQUESTED. WE URGE YOU TO CONTACT YOUR CLIENTS AS PROMPTLY AS POSSIBLE. PLEASE NOTE THAT THE OFFER AND WITHDRAWAL RIGHTS WILL EXPIRE AT 12:00 MIDNIGHT, NEW YORK CITY TIME, ON FRIDAY, MARCH 24, 2000, UNLESS THE OFFER IS EXTENDED. Please note the following: 1. The tender price is $23.50 per Share, net to the seller in cash, without interest. 2. The Offer is being made for any and all of the outstanding Shares. There is no minimum number of Shares required to be tendered. 3. Tendering stockholders will not be obligated to pay brokerage fees or commissions or, except as set forth in Instruction 6 of the Letter of Transmittal, stock transfer taxes on the transfer of Shares pursuant to the Offer. However, federal income tax backup withholding at a rate of 31% may be required unless an exemption is available or unless the required taxpayer identification information is provided. See "Important Tax Information" of the Letter of Transmittal. 4. The special committee of the independent directors of the board of directors of the Company (the "Company Board") has unanimously recommended that the Company Board approve the Offer and the Merger (as defined in the Offer to Purchase) and approve and adopt the Merger Agreement. The Company Board has determined that the Merger is advisable and in the best interests of the stockholders of the Company, and has approved the Merger. The Company Board has also approved the Offer and recommended the Offer to the Company's stockholders. 5. Notwithstanding any other provision of the Offer, payment for Shares accepted for payment pursuant to the Offer will in all cases be made only after timely receipt by the Depositary of (a) Certificates pursuant to the procedures set forth under "THE TENDER OFFER--Procedures for Tendering Shares" of the Offer to Purchase or a timely Book-Entry Confirmation (as defined in the Offer to Purchase) with respect to such Shares, (b) a properly completed and duly executed Letter of Transmittal (or a manually signed facsimile thereof) with any required signature guarantees or an Agent's Message (as defined in the Offer to Purchase) in connection with a book-entry delivery of Shares, and (c) any other documents required by the Letter of Transmittal. Accordingly, tendering stockholders may be paid at different times depending upon when Certificates for Shares or Book-Entry Confirmations are actually received by the Depositary. In order to take advantage of the Offer, (i) a properly completed and duly executed Letter of Transmittal (or a manually signed facsimile thereof) with any required signature guarantees or an Agent's Message in connection with a book-entry delivery of Shares, and any other documents required by the Letter of Transmittal should be sent to the Depositary and (ii) Certificates representing the tendered Shares or a timely Book-Entry Confirmation should be delivered to the Depositary in accordance with the instructions set forth in the Letter of Transmittal and the Offer to Purchase. 2 If holders of Shares wish to tender, but it is impracticable for them to forward their Certificates or other required documents or complete the procedures for book-entry transfer prior to the Expiration Date, a tender may be effected by following the guaranteed delivery procedures specified under "THE TENDER OFFER--Procedures for Tendering Shares" of the Offer to Purchase. None of Suez Lyonnaise, Parent or Purchaser or any officer, director, agent or other representative of Purchaser, Parent or Suez Lyonnaise will pay any fees or commissions to any broker, dealer or other person (other than the Depositary and Morrow & Co., Inc. (the "Information Agent") as described in the Offer to Purchase) for soliciting tenders of Shares pursuant to the Offer. Purchaser will, however, upon request, reimburse you for customary mailing and handling expenses incurred by you in forwarding any of the enclosed materials to your clients. Purchaser will pay or cause to be paid any transfer taxes payable on the transfer of Shares to it, except as otherwise provided in Instruction 6 of the Letter of Transmittal. Any inquiries you may have with respect to the Offer should be addressed to the Information Agent or the Dealer Manager at their respective addresses and telephone number set forth on the back cover of the Offer to Purchase. Additional copies of the enclosed materials may be obtained from the Information Agent or from brokers, dealers, commercial banks or trust companies. Very truly yours, T ACQUISITION CORP. NOTHING CONTAINED HEREIN OR IN THE ENCLOSED DOCUMENTS SHALL CONSTITUTE YOU OR ANY OTHER PERSON THE AGENT OF SUEZ LYONNAISE, PARENT, PURCHASER, THE DEPOSITARY, THE INFORMATION AGENT, OR ANY AFFILIATE OF ANY OF THEM, OR AUTHORIZE YOU OR ANY OTHER PERSON TO MAKE ANY STATEMENT OR USE ANY DOCUMENT ON BEHALF OF ANY OF THEM IN CONNECTION WITH THE OFFER OTHER THAN THE ENCLOSED DOCUMENTS AND THE STATEMENTS CONTAINED THEREIN. 3