The largest pumped storage facility in the country is the Bath County Pumped Storage Station in the Allegheny Mountains, on the state line between Virginia and West Virginia. On the surface, it looks like other pumped storage projects, with a medium sized 265-acre upper reservoir, connected by buried penstocks to a power station, located on the shore of lower reservoir, made by damming a creek. The difference is inside the power plant, which has six pump/turbines, each with a capacity exceeding 500 megawatts, more than twice a typical size, enabling the plant to produce as much as 3,003 megawatts, making it the tenth largest electrical generating station in the USA, of any kind. The upper reservoir is 1,200 feet above the power station, and its water level sinks 100 feet over the ten hours it takes to drain through the turbines into the lower reservoir. It takes 11 hours to pump the water back up. The plant is 80% efficient, meaning 20% more power is used to pump the water back up. Construction started in the late 1970s, and the plant opened in 1985, costing more than four billion in today’s dollars. It was the largest pumped storage facility in the world until 2021, when a 3,600-megawatt plant opened in China.
