The Bath County Pumped Storage Station is a pumped storage hydroelectric power plant, which is described as the "largest battery in the world", with a maximum generation capacity of 3,003 MW, an average of 2,772 MW, and a total storage capacity of 24,000 MWh. The station is located in the northern corner of Bath County, Virginia, on the southeast side of the Eastern Continental Divide, which forms this section of the border between Virginia and West Virginia. The station consists of two reservoirs separated by about in elevation. It was the largest pumped-storage power station in the world until 2021, when it was surpassed by the Fengning Pumped Storage Power Station. Construction on the power station, with an original capacity of , began in March 1977 and was completed in December 1985 at a cost of $1.6 billion, Voith-Siemens upgraded the six turbines between 2004 and 2009, increasing power generation to 500.5 MW and pumping power to for each turbine. Bath County Station is jointly owned by Dominion Generation (60%) and FirstEnergy (40%), and managed by Dominion. It stores energy for PJM Interconnection, a regional transmission organization in 13 states and the District of Columbia. Design The upper and lower reservoirs are created by earth and rock-filled embankment dams. The upper reservoir dam is high, long and has a structural volume of . The upper reservoir on Little Back Creek has a surface area of and storage capacity of . The lower reservoir dam on Back Creek is high and in length. It has a structural volume of and creates a reservoir with a surface area of and storage capacity of . Connecting the upper reservoir to the power station are three water conduits between long. The conduits each lead to a shaft which bifurcates into two penstocks (for a total of six) before reaching the turbines. Each penstock is in diameter and between in length. Maximum static pressure from the top of the water delivery system to the turbines is . Method of operation Water is released from the upper reservoir during periods of high demand and is used to generate electricity. What makes this different from other hydroelectric dams is that during times of low demand, power is taken from coal, nuclear, and other power plants and is used to pump water from the lower to the upper reservoir. Although this plant uses more power than it generates,