Which renewable-energy storage method pumps water uphill when electricity is plentiful and releases it through turbines later?

Pumped-storage hydroelectricity stores energy by pumping water uphill and later releasing it through turbines.

A pumped-storage plant has two reservoirs at different elevations. When electricity is abundant or inexpensive, pumps move water from the lower reservoir to the upper one. When demand rises, the water flows downhill through reversible pump-turbines, generating electricity much like a conventional hydropower station.

The method is often described as a giant rechargeable battery, although it stores energy mechanically as gravitational potential energy rather than chemically. It can respond quickly to changes in demand and help balance variable renewable sources such as wind and solar power. The plant consumes more electricity pumping water than it later returns, so its round-trip efficiency is below 100 percent.

Pumped storage is not itself a primary energy source: it shifts electricity through time. It can use electricity from renewable or non-renewable generators, depending on the grid. This distinguishes it from ordinary reservoir hydropower, where natural river inflows provide the main energy input.