Pumped-Storage hydro power facilities
"Pumped-storage" projects use off-peak electricity to pump water from a lower reservoir to an upper reservoir. During periods of high electrical demand, the water is released back to the lower reservoir to generate electricity. There are only about 40 pumped-storage facilities in the U.S., but some are very large. (Note: the Power Scorecard rates electricity from pumped storage on the basis of the electricity used to pump the water and the impacts of the storage operations.