Capitol Power Plant Evolution
In 1950 the steam boilers were replaced with modern coal-fired steam generators. The original refrigeration equipment was replaced, doubling the plant's air-conditioning capacity. At the same time the plant's electricity generating capacity had reached its limit and it was therefore decided to abandon production and transfer loads to the local electrical utility, PEPCO.
Another expansion of the Power Plant was authorized in 1958 to accommodate the latest enlargement of the Capitol, the construction of an additional House office building, and other projects. Additional air-conditioning capacity was also provided. In anticipation of the construction of the Library of Congress James Madison Memorial Building another enlargement was authorized in 1970. Construction of the Capitol Visitor Center prompted the plant's expansion in the early 21st Century.