Plant today, he would not recognize it. Since 1910, the plant has undergone
numerous changes, such as the addition of three refrigeration plants to cool
congressional facilities during the hot and humid Washington summers, the
decommissioning of electric generation and the expansion of fuel capacity.
State-of-the-Art From the Start
The need for a central heating and electric plant became apparent in the beginning of the 20th century when planning began for the
first House office building (known today as the Cannon House Office
Building). Prior to the central plant’s construction, the Capitol and other
buildings each had their own “power plant,” but it was determined that a
central power plant would be much more efficient in meeting the increasing energy demands as new congressional office buildings were constructed. Congress authorized the Capitol Power Plant’s construction with the
passage of the Act of April 28, 1904.
The plant was built on public land close to the Anacostia River
and conveniently located near railroad tracks so deliveries could be
easily made. At the time, the idea of a central power plant was a new and
popular concept. Woods decided to use the most modern technology
available, making Congress a leader in the country with its own state-of-the-art central plant. What Woods did not know was the extent of the
future growth of the Capitol complex and how the demand generated
by that growth would require the plant to expand and evolve.
For example, in the 1930s, air conditioning was quickly becoming an
indispensable part of life on Capitol Hill. In 1935, Congress appropriated
funds for the installation of central refrigeration equipment to circulate
chilled water throughout the various buildings, thereby providing central
air conditioning. This allowed Congress to work during the hottest months
of the year for the first time. Constructed from 1936 to 1938, the centralized chilled-water plant at the Capitol Power Plant was the first large-scale
refrigeration facility of its type in the world and the largest district cooling
system in the United States. While authentic construction documents are
no longer available, a 1937 article in The New York Times reported that the
original contract was awarded to York Ice Machinery Corp. According to
1955 records, the original equipment included six 800-ton, 100 HP, 6,600
Volt, 275 RPM synchronous-motor electrically driven chillers.
At the time it was placed in service, the Capitol Power
Plant’s district cooling system was the largest in the
The Capitol Power Plant Today
Today, the Capitol Power Plant provides steam to 23 buildings
and chilled water to 20 buildings located across the Capitol complex,
representing nearly 18 million sq ft of space. In addition to the U.S.
Courtesy Architect of the Capitol.
With the design capacity to generate 620,000 lb/hr of steam and 40,200 tons
of refrigeration, the Capitol Power Plant is the single largest contributor to
energy reduction in congressional facilities.
Capitol and the House and Senate office buildings, the plant serves the
U.S. Supreme Court, the Library of Congress buildings and U.S. Botanic
Garden, as well as other facilities on Capitol Hill that are not managed
by the Architect of the Capitol (AOC), the federal agency responsible
for the development and maintenance of the U.S. Capitol complex
buildings and grounds.
The energy used by the Capitol Power Plant represents almost
64 percent of the total energy consumed by facilities maintained by the
AOC. The plant has the design capacity to generate 620,000 lb/hr of
steam and 40,200 tons of refrigeration. The steam plant contains seven
natural gas-fired boilers to generate steam for heating. In addition, the
Capitol Power Plant operates seven electric-driven mechanical chillers
and four plate-and-frame heat exchangers (used for free cooling) to
produce chilled water for cooling.
Given the magnitude of the energy consumption at the Capitol
Power Plant, it is important to note that it is the single largest contributor to energy reduction in congressional facilities. To further increase its
energy efficiency, the AOC began a modernization project in 2003 to
expand the West Refrigeration Plant (completed in 1978) and decommission the East Refrigeration Plant (circa 1938). The chillers in use in
the East Refrigeration Plant had been operating since 1958, and were
clearly nearing the end of their useful lives. This project also was necessary to meet the increased load of the new Capitol Visitor Center and
other building additions, renovations and modernizations across the
By 2008, the AOC completed the expansion of the West Refrigeration
Plant, which included the addition of three 5,400-ton chillers with variable-speed pumping and free-cooling capabilities. The modernization project
also included the installation of a state-of-the-art distributed control system
in the heating plant to replace the vintage 1950s pneumatic controls.