EXHIBIT NO. 21 LIST OF SUBSIDIARIES OF UIL HOLDINGS CORPORATION STATE OR JURISDICTION OF INCORPORATION OR NAME UNDER WHICH NAME OF SUBSIDIARY ORGANIZATION SUBSIDIARY DOES BUSINESS ------------------ --------------------- ------------------------ The United Illuminating Company (1) Connecticut The United Illuminating Company United Resources, Inc. (1) Connecticut United Resources, Inc. Xcelecom, Inc. (2) Connecticut Xcelecom, Inc. American Payment Systems, Inc. (2) Connecticut American Payment Systems, Inc. United Bridgeport Energy, Inc. (2) Connecticut United Bridgeport Energy, Inc. United Capital Investments, Inc. (2) Connecticut United Capital Investments, Inc. McPhee Electric Ltd., LLC (3) Connecticut McPhee Electric Ltd., LLC McPhee Utility Power and Signal, Ltd. (3) Connecticut McPhee Utility Power and Signal, Ltd. Thermal Energies, Inc. (3) Connecticut Thermal Energies, Inc. Allan Electric Co., Inc. (3) New Jersey Allan Electric Co., Inc. Brite-Way Electrical Contractors, Inc. (3) New Jersey Brite-Way Electrical Contractors, Inc. The DataStore, Incorporated (3) New Jersey The DataStore Incorporated Orlando Diefenderfer Electrical Contractors, Inc. (3) Pennsylvania Orlando Diefenderfer Electrical Contractors, Inc. Johnson Electric Co., Inc.(3) Connecticut Johnson Electric Co., Inc. M. J. Daly & Sons, Inc. (3) Connecticut M. J. Daly & Sons, Inc. 4Front Systems, Inc. (3) North Carolina 4Front Systems, Inc. APS Card Services, Inc. (4) Connecticut APS Card Services, Inc. CellCards of Illinois, LLC (4) Illinois CellCards of Illinois, LLC Souwestcon Properties, Inc. (5) Connecticut Souwestcon Properties, Inc. JBL Electric, Inc. (6) New Jersey JBL Electric, Inc. J. E. Richards, Incorporated (3) Maryland J. E. Richards, Incorporated Richards Electric, Incorporated (3) Maryland Richards Electric, Incorporated - ---------------------- (1) Subsidiary of UIL Holdings Corporation (2) Subsidiary of United Resources, Inc. (3) Subsidiary of Xcelecom, Inc. (4) Subsidiary of American Payments Systems, Inc. (5) Subsidiary of United Capital Investments, Inc. (6) Subsidiary of Allan Electric Co., Inc.