# Pumped hydro storage: Overview

How hilltop lakes became the world's biggest battery

Source page: https://www.materialinsights.org/energy/e_pumped_hydro/overview/

How hilltop lakes became the world's biggest battery What this tile covers Pumping water uphill when power is spare and running it back through turbines when needed; the largest grid store in the world. Share of use.05% share of world stored energy (2025)

Share of the world's stored energy (energy capacity held, TWh, latest year 2019 to 2026) across the forms with figures, about 22,551 TWh; fuel stocks dominate. Battery and other stores count capacity, not state of charge (calculated) The IEA put reservoir storage (1,500 TWh) at about 170 times the energy held by pumped storage, about 8.8 TWh around 2020, when capacity was about 160 GW. Scaling by capacity to 201 GW at end 2025 (IHA) gives about 11.1 TWh, assuming similar storage hours per GW. Of 22,551 TWh. Source: [Year of the water battery: global pumped storage capacity surpasses 200 GW (2026 World Hydropower Outlook)](https://www.hydropower.org/news/year-of-the-water-battery-global-pumped-storage-capacity-surpasses-200-gw), International Hydropower Association.

#### Key facts

| **Duration** | Hours to days |
|---|---|
| **Chain** | Electrical → pump → gravitational → turbine → electrical |

#### Included from the reference tables

- Pumped hydro, including underground and seabed variants

#### Linked to the material world
[H₂O Water](https://www.materialinsights.org/commodities/water/)

#### Also in Mechanical
[Grv Gravity storage](https://www.materialinsights.org/energy/e_gravity/)[Fly Flywheels and small mechanical stores](https://www.materialinsights.org/energy/e_flywheels/)[CAES Compressed-air and CO2 storage](https://www.materialinsights.org/energy/e_caes/)[LAES Liquid air storage](https://www.materialinsights.org/energy/e_liquid_air/)

Explore paths from here
 More on this tile in the tabs above: science and technology, engineering and performance, economics, impact and additionality, what to track.

## Other sections

- [Summary](https://www.materialinsights.org/energy/e_pumped_hydro/index.md)
- [Correlation](https://www.materialinsights.org/energy/e_pumped_hydro/correlation/index.md)
- [Science and technology](https://www.materialinsights.org/energy/e_pumped_hydro/sg-sci/index.md)
- [Engineering and performance](https://www.materialinsights.org/energy/e_pumped_hydro/sg-eng/index.md)
- [Economics](https://www.materialinsights.org/energy/e_pumped_hydro/sg-econ/index.md)
- [Impact and additionality](https://www.materialinsights.org/energy/e_pumped_hydro/sg-impact/index.md)
- [What to track](https://www.materialinsights.org/energy/e_pumped_hydro/tracking/index.md)
- [Relationships](https://www.materialinsights.org/energy/e_pumped_hydro/links/index.md)