Pumped Storage

A clean energy storage method that moves water between reservoirs at different elevations to store and generate electricity.

Pumped storage is a utility-scale energy storage method that moves water between two reservoirs at different elevations to store and generate electricity. During periods of low electricity demand or high renewable energy generation, excess grid power is used to pump water from the lower reservoir to the upper reservoir. When electricity demand peaks or renewable output drops, the stored water is released downhill through turbines, generating electricity to supply the grid. For clean energy and infrastructure investors, pumped storage represents a mature, highly efficient technology essential for balancing grid volatility caused by intermittent wind and solar power. It provides grid stability, load balancing, and peaking capacity. Investors typically evaluate companies involved in the construction, turbine manufacturing, or ownership and operation of these capital-intensive, long-duration assets. While pumped storage projects offer predictable, long-term cash flows often backed by government contracts or regulated rates, they require massive upfront capital expenditure and face lengthy regulatory approval processes. Investors must monitor construction timelines, environmental compliance risks, and the round-trip efficiency of the facility, which measures how much energy is recovered relative to how much was used to pump the water.

A pumped storage facility uses 100 megawatt-hours (MWh) of off-peak electricity to pump water to its upper reservoir. When the water is released during peak hours, the turbines generate 80 MWh of electricity. The round-trip efficiency of this facility is calculated as 80 MWh / 100 MWh = 80%.