LONDON — Utilities and governments are reviving pumped hydro projects worldwide in 2025 to store renewable electricity for the evening peak as grids strain under rising demand. By pumping water uphill when power is plentiful and releasing it through turbines when prices spike, the plants act as durable “water batteries,” Dec. 22, 2025.
Why pumped hydro is back in the spotlight
Pumped hydro is not new, but the business case is. As solar floods grids at midday and wind output swings, operators are looking for storage that can run for hours, recharge daily and keep working for decades without relying on scarce minerals.
The International Energy Agency recently called pumped-storage hydro the world’s largest form of electricity storage, saying it has the capacity to hold “30 times more power than batteries.”
Big numbers, bigger pipeline
Momentum is accelerating in Asia and spreading elsewhere. The IEA’s Renewables 2025 outlook forecasts annual additions of pumped-storage hydropower will double to 16.5 gigawatts by 2030, with China accounting for more than 60% of the growth.
The International Hydropower Association’s 2025 World Hydropower Outlook says global hydropower capacity grew 24.6 gigawatts in 2024, including 8.4 gigawatts of pumped storage. It estimates the pumped-storage development pipeline at about 600 gigawatts, a sign developers are treating long-duration storage as core grid infrastructure.
What makes pumped hydro a different kind of grid battery
Pumped hydro stores electricity as gravity, not chemicals. Water is moved uphill when electricity is cheap, then released through turbines to generate power later — a mechanical cycle that can pair with renewables and provide flexibility as dispatchable fossil plants retire.
In the United States, the U.S. Department of Energy says pumped storage makes up 96% of utility-scale energy storage, underscoring how much of today’s storage still depends on reservoirs and elevation.
Building new plants, though, is slow and politically charged. Permitting can take years, costs run high upfront, and local opposition often centers on land and water impacts.
Developers are trying to widen the map. British startup RheEnergise is testing a system that uses a denser mineral-based fluid instead of water; its CEO, Stephen Crosher, told WIRED that in the pilot plant “you want it to be really runny.” The pitch: more potential sites, smaller reservoirs and faster build times.
The “water battery” metaphor has been around for years. A 2018 International Hydropower Association paper, “The world’s water battery”, said pumped storage dominated installed global energy storage capacity at the time. A 2019 IEA note, asking whether pumped storage would expand more quickly than stationary battery storage, projected 26 gigawatts of pumped-storage growth over 2018-23.
Now, with major renewable buildouts colliding with reliability concerns, pumped hydro is being pulled from the margins to the center of grid planning — if governments can speed approvals and markets can pay for storage built to last.
