How Pumped Storage Hydropower Works

How Does Pumped Storage Hydropower Work?

Pumped storage hydropower (PSH) is one of the most-common and well-established types of energy storage technologies. It currently accounts for 96% of all utility-scale energy storage capacity in the United States. PSH facilities store and generate electricity by moving water between two reservoirs at different elevations. This energy storage is vital to grid reliability. Today, the U.S. pumped storage hydropower fleet includes about 22 gigawatts of electricity-generating capacity and 550 gigawatt-hours of energy storage with facilities in every region of the country.

PSH is also the dominant commercialized technology for long-duration storage, which makes it increasingly valuable as the power system evolves.

How Exactly is Electricity Generated?

As demonstrated in the animation, PSH plants operate much like conventional hydropower plants, except PSH has the ability to use the same water over and over again. When power from the plant is needed, water flows from the upper reservoir 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.