 Cruachan was one of the first reversible pumped @-@ storage systems , where the same turbines are used as both pumps and generators . Previous pumped @-@ storage systems used separate pumps with a network of pipes to return water to the upper reservoir , making them much more expensive to build than conventional hydroelectric systems . Cruachan is predated by the smaller 232 megawatts ( 311 @,@ 000 hp ) Lünerseewerk ( de ) of 1958 and the 360 megawatts ( 480 @,@ 000 hp ) Ffestiniog Power Station of 1963 . It is one of four pumped storage schemes in the UK . 
