EXHIBIT 21 12/31/98 Trigen Energy Corporation And Subsidiaries U.S. Corporations Incorporated Baltimore Thermal Development Corporation Maryland Catalyst Steam Corporation Delaware Philadelphia United Power Corporation Delaware Philadelphia Thermal Development Corporation Pennsylvania Philadelphia Steam Development Corporation Pennsylvania Philadelphia Thermal Services Corporation Pennsylvania St. Louis Thermal Development Corporation Missouri Trenton Energy Corporation Delaware Tulsa Cold Storage, Inc. Delaware Trigen-Alabama Energy Corporation Delaware Trigen-Baltimore Energy Corporation Maryland Trigen-BioPwer, Inc. North Carolina Trigen-Boston Energy Corporation Delaware Trigen Building Services Corporations Delaware Trigen-Chicago Energy Corporation Delaware Trigen-College Park Energy Corporation Maryland Trigen-Colorado Energy Corporation Delaware Trigen Development Corporation Delaware Trigen Energia, Inc. Delaware Trigen Energy Corporation Delaware Trigen-Ewing Power, Inc. Delaware The Trigen Foundation Delaware Trigen Fuels Corporation Delaware Trigen-Glen Cove Energy Corporation Delaware Trigen-Golden Energy Corporation Delaware Trigen Insulation Corporation Delaware Trigen-Kansas City Energy Corporation Delaware Trigen Lindbergh Corporation Delaware Trigen-Mid-Atlantic Development Corporation Delaware Trigen M/I Corporation Delaware Trigen-Missouri Energy Corporation Delaware Trigen-Nassau Energy Corporation Delaware Trigen National Capital, Inc. Delaware Trigen-New England Energy Corporation Delaware Trigen-New Jersey Development Corporation Delaware Trigen-Oklahoma Energy Corporation Delaware Trigen-Oklahoma City Energy Corporation Delaware Trigen-Philadelphia Energy Corporation Pennsylvania Trigen Power Resources, Inc. Delaware Trigen-Schuylkill Cogeneration, Inc. Pennsylvania Trigen Services Corporation Delaware Trigen Services Of Baltimore, Inc. Delaware Trigen Services Of Florida, Inc. Delaware Trigen Services Of Illinois, Inc. Delaware Trigen Services Of Missouri, Inc. Delaware Trigen Services Of Ohio, Inc. Delaware Trigen Services Of St. Paul, Inc. Delaware Trigen Solutions, Inc. Delaware Trigen-St. Louis Energy Corporation Missouri Trigen-Tulsa Energy Corporation Delaware United Thermal Corporation Delaware United Thermal Development Corporation Delaware United Thermal Services Corporation Delaware Canadian Corporations - --------------------- 3003252 Nova Scotia Limited Nova Scotia Trigen Energy Canada Inc. Canada Partnerships - ------------ Baltimore Steam Company Maryland Gray's Ferry Cogeneration Partnership Ohio Valley Coke & Energy LLC Delaware Thermal Science Technologies LLC Delaware Trigen-Barford Company LLC Delaware Trigen-Cinergy Solutions LLC Delaware Trigen-Cinergy Solutions of Baltimore LLC Delaware Trigen-Cinergy Solutions Of Boca Raton, LLC Delaware Trigen-Cinergy Solutions Of Cincinnati LLC Ohio Trigen-Cinergy Solutions of College Park LLC Delaware Trigen-Cinergy Solutions Of Illinois L.L.C. Delaware Trigen-Cinergy Solutions Of Orlando LLC Delaware Trigen-Cinergy Solutions Of St. Paul LLC Delaware Trigen-Cinergy Solutions Of Tuscola, LLC Delaware Trigen-HQ Energy Services LLC Delaware Trigen-Nations Energy Company, LLLP Colorado Trigen-Peoples District Energy Company LLP Illinois Trigen-Trenton Energy Company, L.P. Delaware Canadian Partnerships - --------------------- NSP Trigen Incorporated Nova Scotia