Pumped hydro is a method of storing energy by moving water between two reservoirs at different elevations. During periods of low electricity demand, excess energy is used to pump water from the lower reservoir to the upper one. This process converts electrical energy into gravitational potential energy. When electricity demand is high, the stored water is released back down to the lower reservoir, passing through turbines that generate electricity. This system helps balance supply and demand, making it a valuable tool for integrating renewable energy sources like solar and wind into the power grid.