AOC, Capitol Power Plant
Capitol Power Plant is a natural gas-fired combustion turbine facility with 7.5 MW of nameplate capacity in the District of Columbia. It is owned and operated by the Architect of the Capitol, the federal legislative-branch agency responsible for the U.S. Capitol campus. The plant has supplied steam and chilled water to the U.S. Capitol, the Supreme Court, the Library of Congress and roughly twenty other buildings on Capitol Hill since December 1910, though it stopped generating grid electricity for the complex in 1951. Between 2009 and the early 2010s the plant phased out coal in favor of natural gas as its primary fuel. In 2018 it commissioned a 7.5 MW natural-gas cogeneration (combined heat and power) unit, a $57 million project built for a 20-year payback that lifted the plant's combined efficiency to roughly 75%. No whole-plant or unit retirement is scheduled; the single gas turbine, CTG1, that came online in August 2018 remains the plant's only generator today.