Gravitational Potential Energy

The Hoover Dam holds back 35 billion cubic metres of water — enough to flood a small country several metres deep. That water isn't moving, but it stores an absolutely COLOSSAL amount of energy just by being high up. When water falls 180 metres through turbines, gravitational potential energy converts to kinetic, then to electrical. The dam generates 4 billion kilowatt-hours per year — enough for 1.3 million homes! All that power from water that was lifted by the Sun evaporating oceans millions of years ago. Height = stored energy, waiting to be released.