1 EXHIBIT 21 TRIGEN ENERGY CORPORATION & SUBSIDIARIES U.S. CORPORATIONS INCORPORATED - ---------------------------------------------------------------------------- --------------- Baltimore Thermal Development Corporation................................... Maryland Catalyst Steam Corporation.................................................. Delaware Ewing Power Systems, Inc. .................................................. Delaware Ohio Thermal Energy Corporation............................................. Ohio Philadelphia Steam Development Corporation.................................. Pennsylvania Philadelphia Thermal Development Corporation................................ Pennsylvania Philadelphia Thermal Services Corporation................................... Pennsylvania Philadelphia United Power Corporation....................................... Delaware St. Louis Thermal Development Corporation................................... Missouri Trenton Energy Corporation.................................................. Delaware Trigen Building Services Corporation........................................ Delaware Trigen Development Corporation.............................................. Delaware Trigen Energy Corporation................................................... Delaware Trigen Energia, Inc. ....................................................... Delaware Trigen Fuels Corporation.................................................... Delaware Trigen Insulation Corporation............................................... Delaware Trigen Lindbergh Corp....................................................... Delaware Trigen M/I Corporation...................................................... Delaware Trigen Services Corporation................................................. Delaware Trigen Solutions, Inc....................................................... Delaware Trigen-Baltimore Energy Corporation......................................... Maryland Trigen-Boston Energy Corporation............................................ Delaware Trigen-Chicago Energy Corporation........................................... Delaware Trigen-Colorado Energy Corporation.......................................... Delaware Trigen-Kansas City Energy Corporation....................................... Delaware Trigen-Missouri Energy Corporation.......................................... Delaware Trigen-Nassau Energy Corporation............................................ Delaware Trigen-New England Energy Corporation....................................... Delaware Trigen-Oklahoma City Energy Corporation..................................... Delaware Trigen-Oklahoma Energy Corporation.......................................... Delaware Trigen-Philadelphia Energy Corporation...................................... Pennsylvania Trigen-Schuylkill Cogeneration, Inc......................................... Pennsylvania Trigen-St. Louis Energy Corporation......................................... Missouri Trigen-Tulsa Energy Corporation............................................. Delaware Tulsa Cold Storage, Inc..................................................... Delaware United Thermal Corporation.................................................. Delaware United Thermal Development Corporation...................................... Delaware United Thermal Services Corp................................................ Delaware CANADIAN CORPORATIONS Trigen Energy Canada, Inc................................................... Canada Trigen-London District Energy Corporation................................... Canada PARTNERSHIPS Baltimore Steam Company..................................................... Maryland Trigen-Nations Energy Company LLLP.......................................... Colorado Trigen-Trenton Energy Company LP............................................ Delaware