PSH plants operate much like conventional hydropower plants, except PSH has the ability to use the same water over and over again. To generate electricity when power from the plant is needed, water flows from the upper reservoir, because of gravity, through turbine(s) that rotate generator(s) to produce electricity. The water then flows into the lower reservoir where it remains until electricity demand lowers. When this occurs, the turbines spin backward to pump the water back into the upper reservoir so it can once again be used to generate electricity when needed.