Exhibit 21 TRIGEN ENERGY CORPORATION AND SUBSIDIARIES Baltimore Steam Company Baltimore Thermal Development Corporation Catalyst Steam Corporation Energy Equipment Leasing LLC Gray's Ferry Cogeneration Partnership 3003252 Nova Scotia Limited NSP Trigen Incorporated Ohio Thermal Energy Corp. Ohio Valley Coke & Energy LLC Owings Mills Energy Equipment Leasing LLC Philadelphia United Power Corporation Philadelphia Thermal Development Corporation Philadelphia Steam Development Corporation Philadelphia Thermal Services Corporation St. Louis Thermal Development Corporation Thermal Technologies, Inc. Trenton Energy Corporation Tulsa Cold Storage, Inc. Trigen Acquisitions Corp. Trigen-Alabama Energy Corporation Trigen-Baltimore Energy Corporation Trigen-Barford Company LLC Trigen-Biopower, Inc. Trigen-Boston Energy Corporation Trigen Building Services Corporation Trigen-Chicago Energy Corporation TRIGEN-CHOLLA LLC Trigen-Cinergy Solutions LLC TRIGEN-CINERGY SOLUTIONS OF ASHTABULA LLC TRIGEN-CINERGY SOLUTIONS OF BALTIMORE LLC Trigen-Cinergy Solutions of Boca Raton, LLC Trigen-Cinergy Solutions of Cincinnati LLC TRIGEN-CINERGY SOLUTIONS OF COLLEGE PARK LLC TRIGEN-CINERGY SOLUTIONS OF DANVILLE Trigen-Cinergy Solutions of Illinois LLC Trigen-Cinergy Solutions of Orlando LLC TRIGEN-CINERGY SOLUTIONS OF OWINGS MILLS LLC Trigen-Cinergy Solutions of Rochester LLC TRIGEN-CINERGY SOLUTIONS OF SAN DIEGO LLC TRIGEN-CINERGY SOLUTIONS OF SILVER GROVE LLC Trigen-Cinergy Solutions of The Southeast LLC Trigen-Cinergy Solutions of St. Paul LLC Trigen-Cinergy Solutions of Tuscola, LLC Trigen-College Park Energy Corporation Trigen-Colorado Energy Corporation TRIGEN-DELAWARE VALLEY ENERGY CORPORATION Trigen Development Corporation Trigen Energia, Inc. Trigen Energy Canada Inc. Trigen Energy Corporation Trigen-Ewing Power, Inc. The Trigen Foundation Trigen Fuels Corporation Trigen-Glen Cove Energy Corporation Trigen-Golden Energy Corporation Trigen-HQ Energy Services LLC Trigen Innovations, Inc. Trigen Insulation Corporation Trigen-Kansas City Energy Corporation Trigen Lindbergh Corporation Trigen-Maryland Energy Corporation Trigen-Maryland Steam Corporation Trigen-Mid-Atlantic Development Corporation Trigen M/I Corporation Trigen-Missouri Energy Corporation Trigen-Nassau Energy Corporation Trigen National Capital, Inc. Trigen-Nations Energy Company, LLLP Trigen-New England Energy Corporation Trigen-New Jersey Development Corporation Trigen-Oklahoma Energy Corporation Trigen-Oklahoma City Energy Corporation Thermal Science Technologies LLC Trigen-Peoples District Energy Company TRIGEN-PHILADELPHIA ENERGY CORPORATION Trigen Power Resources, Inc. Trigen-Schuylkill Cogeneration, Inc. Trigen Services Corporation Trigen Services of College Park, Inc. Trigen Services of Illinois, Inc. Trigen Services of San Diego, Inc. Trigen Energy Services, Inc. Trigen Solutions, Inc. Trigen-St. Louis Energy Corporation TRIGEN-SYRACUSE ENERGY CORPORATION Trigen-Trenton Energy Company, L.P. Trigen-Tulsa Energy Corporation United Thermal Corporation United Thermal Development Corporation United Thermal Services Corporation