High Quality Content by WIKIPEDIA articles! The Ffestiniog Power Station is a 360 MW pumped-storage hydroelectricity scheme near Ffestiniog, in Gwynedd, north-west Wales, United Kingdom. The power station at the lower reservoir has four water turbines, which can generate 360 megawatts of electricity within 60 seconds of the need arising. The station, commissioned in 1963, was the first major pumped storage system in the UK. The upper reservoir is Llyn Stwlan which discharges 27 m3/s (953 cu ft/s) of water to the turbine generators at the power station on the bank of Tan-y-Grisiau reservoir.