Originally constructed in 1896, Foyers was the first large-scale commercial hydro-electric scheme in the UK. It was converted in 1975 to focus primarily on pumped storage, & with a soon-to-be-upgraded capacity of 305 MW, Foyers is one of 4 pumped storage power stations in the UK (the others being Cruachan, Dinorwig & Ffestiniog). Pumped storage turbines can be brought from a standstill to full power output in less than two minutes, which makes these power stations extremely responsive to demand.