This power station was put into service in 1965 and has a total capacity of 400 megawatts and an annual production of 450 units of electricity. The turbines are works of technological ingenuity and are reversible, being used to pump water from Loch Awe to the upper reservoir on the slopes of Ben Cruachan, which in turn feeds an underground power station in the heart of the mountain. A tunnel 1.5 km long leads to the machine room, hewn from the rock.