# Pumped hydro storage

Pumping water uphill when power is spare and running it back through turbines when needed; the largest grid store in the world.

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

Storage · Mechanical · No. 78

- Storage
- Duration: Hours to days
 Storage · Mechanical · Foundation · Energy

Over 90% of the world's stored energy sits as water in hilltop lakes, in plants that can run for a century.

Chart: Illustration: Pumped hydro storage

##### Where it comes from

Chart: Map of where it comes from

Reversible machines pump water uphill when power is cheap and let it run back to generate; China's Tiantai plant uses a 724 m drop.

##### Three things to know

1. About 80% of the electricity used to pump water uphill comes back when it falls through the turbines.
2. Adding hours is cheap: a 24-hour plant costs USD 143/kWh against USD 263/kWh for a 10-hour one (2021 data).
3. Each plant is a 6 to 8 year civil project, and the hardest part is finding hills, water and land.

##### The journey

1. 1 **Spare power**Cheap midday solar or night wind
2. 2 **Pumping**Water lifted to the upper reservoir
3. 3 **Holding**Stored as height, for hours to days
4. 4 **Release**Water falls back through pump-turbines
5. 5 **Grid**Evening peaks, reserves and multi-day lulls
 Covered in [Making electricity: thermal, nuclear, hydro, wind and solarEnergy](https://www.materialinsights.org/learn/energy/making-electricity/)[Storing energy: from fuel stocks to batteriesEnergy](https://www.materialinsights.org/learn/energy/storing-energy/)[Energy transitions and climateEnergy](https://www.materialinsights.org/learn/energy/energy-transitions-climate/)

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## Other sections

- [Overview](https://www.materialinsights.org/energy/e_pumped_hydro/overview/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)