The following page lists all power stations that are larger than 1,000 in installed generating capacity, which are currently operational or under construction. Those power stations that are smaller than 1,000 MW, and those that are decommissioned or only at a planning/proposal stage may be found in regional lists, listed at the end of the page. A pumped-storage hydroelectricity generally consists of two water reservoirs at different heights, connected with each other. At times of low electrical demand, excess generation capacity is used to pump water into the upper reservoir. When there is higher demand, water is released back into the lower reservoir through a, generating electricity. Pumped storage plants usually use reversible turbine/generat.