The Capitol Power Plant is the Capitol Complex's centralized provider of utility services not available from other sources. The Capitol Power Plant also houses several functions related to the Legislative Branch Telecommunications Network, Security, and also provides dedicated space for satellite communication dishes providing electronic feeds to the CATV system. The Capitol Power Plant employees operate and maintain a central steam plant rated at 620,000 pounds per hour that provides steam for heating, and a central refrigeration plant rated at approximately 35,000 tons capacity that provides chilled water for air conditioning, and all the tunnel distribution and metering systems associated with delivering these utilities.

The Architect of the Capitol performs his duties in connection with the plant under authority of the Act of March 4, 1911 (36 Stat. 1414). The Plant itself has been in operation since December 1, 1910. Heating and air conditioning are provided for several Legislative Branch clients within the Capitol complex: the United States Capitol Building, the Senate Office Buildings and the Senate Garage, the House Office Buildings and Underground Garages, and the Library of Congress Buildings. Heating is also provided for the United States Botanic Garden. The Capitol Power Plant also provides steam and chilled water on a reimbursable basis for heating and air conditioning to several other clients, some of whom are not Legislative Branch entities. Among these, heating is provided for the Government Printing Office and Postal Square, and heating and air conditioning are provided for the Folger Shakespeare Library, Union Station complex, the United States Supreme Court Building, and the Thurgood Marshall Federal Judiciary Building. Fees collected from these clients fully reimburse the Capitol Power Plant's operating and capitalized costs for providing steam and chilled water. It is estimated that $3,985,000 will be collected in fiscal year 2000 and $4,400,000 will be collected in fiscal year 2001.

All electrical energy used throughout the Capitol complex is purchased from the local public utility. Approximately one-half of the electrical load at the Capitol Power Plant has been purchased since September 1950, and the remaining one-half load since September 1951 when generation of all electrical energy at the Capitol Power Plant was discontinued. The energy purchased for all buildings and grounds under the jurisdiction of the Architect of the Capitol is now 60-cycle alternating current, having been converted from 25-cycle alternating current during the period 1951-1963 under funds allowed for such purpose by Congress.