Pumped Storage Hydropower

Pumped storage hydropower is a way to store electricity using water and two reservoirs at different heights. When there is extra electricity, it pumps water up to the higher reservoir. When electricity is needed, it lets the water flow back down through turbines to make power. It works like a giant, rechargeable battery made of water.

Why is it needed?

Solar power is plentiful at noon but disappears at night. Wind power rises and falls with the weather. But people need electricity in the evening peak, when solar is gone. Without storage, extra solar power at noon is wasted, and the evening needs costly or polluting plants. Pumped storage moves cheap daytime power to the evening. It also helps keep the grid stable.

How does it work?

1. Pumping mode: When power is cheap and extra (for example, sunny afternoons), the plant uses electricity to pump water from the lower reservoir to the upper one.
2. Storage: The water waits in the upper reservoir. Its height holds the stored energy.
3. Generating mode: When demand peaks, water flows down through the same machines, which now act as turbines, and electricity is produced.

The same machine works as a pump in one direction and a turbine in the other. It is called a reversible unit. Some energy is lost in each cycle. About 70 to 80% of the power used for pumping comes back as electricity. This is called round-trip efficiency. For example, India's Tehri pumped storage plant has a round-trip efficiency of about 79%.

Types of pumped storage

• On-river (open-loop): Uses reservoirs on a flowing river, often existing dams.
• Off-river (closed-loop): Two reservoirs built away from a river, filled once and then reused. They affect rivers less and can be built faster (about four years).

Official documents say on-stream for on-river and off-stream for off-river. They also list a middle type, off-stream open-loop: one reservoir sits on a river and the other sits away from it.

India's position and examples

Pumped storage is the world's most widely used form of large-scale energy storage. At the end of 2025, the world had about 159.8 GW, according to the International Renewable Energy Agency (IRENA). India ranked fourth with about 7.18 GW, behind China, Japan and the United States.

As of August 2026, India had 10 pumped storage projects in operation, with a total of about 7.43 GW. Another 11 projects of about 15.87 GW were under construction or being implemented. Examples:

• Pinnapuram (Andhra Pradesh): 1,680 MW (6 × 240 MW + 2 × 120 MW), built by Greenko in Kurnool district. It is an off-river closed-loop plant, and it was commissioned in 2025.
• Tehri PSP (Uttarakhand): 1,000 MW (4 × 250 MW), built by THDC. It is India's first variable speed pumped storage plant. It uses the Tehri and Koteshwar dams on the Bhagirathi as its upper and lower reservoirs. All four units were in commercial operation by April 2026.
• Srisailam (Telangana, left bank): 900 MW.
• Purulia (West Bengal): 900 MW.
• Nagarjuna Sagar (Telangana): about 705 MW.
• Kadamparai (Tamil Nadu): 400 MW.
• Bhira and Ghatghar (Maharashtra): 150 MW and 250 MW.

Government plans and policy

• In March 2019, the government declared large hydropower (above 25 MW) as a renewable energy source, which helps pumped storage too.
• In 2023, the Ministry of Power issued Guidelines to Promote Development of Pump Storage Projects. They suggest states ease land and tax costs and allow flexible ways to allot sites.
• In May 2023, the CEA notified the National Electricity Plan (2022-32). This is India's official plan for how much power and storage the country will need. It estimates that by 2031-32, India will need about 73.93 GW of energy storage, able to deliver about 411.4 GWh. Pumped storage makes up 26.69 GW (about 175 GWh) of this. Batteries make up 47.24 GW (about 236 GWh).
• In February 2025, the Ministry of Power notified Tariff-Based Competitive Bidding (TBCB) Guidelines for pumped storage. They set one clear, open way to buy storage from these plants.
• In January 2026, the Central Electricity Authority (CEA) released a Roadmap to 100 GW of Hydro Pumped Storage Projects. The target is about 100 GW by 2035-36. India's identified potential is about 267 GW, and over 75% of it is off-river closed-loop. Maharashtra has the largest identified potential (over 56 GW).
• As of September 2026, the CEA's count of identified potential had grown to about 345.38 GW across 320 projects. About 84% of it (288.71 GW) is off-stream. Maharashtra leads with 67.36 GW, followed by Gujarat with 33.36 GW.
• As of October 2026, the official plan shows 100.81 GW of projects to be commissioned by 2035-36. This would take India's total to about 105.56 GW.
• In November 2026, the Union Cabinet approved a Viability Gap Funding (VGF) scheme of ₹14,500 crore for 92 GWh of grid-scale energy storage. The scheme runs from 2026-27 to 2030-31. Total investment is estimated at about ₹97,600 crore.
• Pumped storage gets the largest share at 60 GWh. Batteries get 30 GWh, and other storage technologies get 2 GWh.
• Public and private discoms (the companies that supply electricity to homes and shops) can get VGF for pumped storage and batteries.
• Capacity is given out through tariff-based competitive bidding.
• The scheme aims to help meet an estimated need of about 411 GWh of storage by 2031-32.

Commonly confused concepts

• Pumped storage vs conventional hydropower: A normal hydro plant only generates electricity from river flow. Pumped storage mostly stores electricity made elsewhere; it uses more power than it gives back, but it gives it back when power is most valuable.
• Pumped storage vs battery storage (BESS): Batteries (like lithium-ion) are fast to build and suited for 2 to 4 hours of storage. Pumped storage costs more upfront but can store energy for 6 hours or more and lasts for decades.
• Open-loop vs closed-loop: Open-loop is connected to a flowing river. Closed-loop is not.
• Storage vs generation capacity: A plant's MW tells how much power it gives at once. MWh (or hours of storage) tells how long it can keep giving it.

Issues, criticism and the way forward

• High upfront cost and long build time: Big civil works like tunnels and dams take years and cost a lot.
• Environmental concerns: Projects in hills and forests can affect forests, wildlife corridors and local communities. The Purulia project faced criticism about its impact on elephant habitats. Environmental groups oppose relaxing impact studies for such projects.
• Suitable sites: Good sites need two reservoirs close together with a large height difference.
• Way forward: Prefer off-river closed-loop sites, speed up clearances without skipping safety checks, and use long-term contracts that pay for the storage service so that projects are financially viable.

Concepts to Know

• Peak demand: The time of day when electricity use is highest, in India usually the evening.
• Grid stability: Keeping the supply of electricity always equal to demand, so voltage and frequency stay steady and there are no blackouts.
• Variable speed unit: A pump-turbine whose speed can change. This lets the plant adjust its power more finely and help the grid better.
• Central Electricity Authority (CEA): India's main technical body for planning the power sector, under the Ministry of Power.
• Battery Energy Storage System (BESS): A large set of batteries connected to the grid to store and release electricity.
• Viability Gap Funding (VGF): Government money that covers part of a project's cost. Some useful projects cost too much to pay for themselves at a price buyers can afford. VGF fills that gap. It is like a relative paying part of your down payment so that your home-loan EMI becomes affordable.
• Tariff-based competitive bidding: An open contest where companies quote the price (tariff) at which they will provide a service. The buyer compares the quotes and picks the winner, as a housing society compares quotes from several painters.
• Gigawatt-hour (GWh): A unit of stored energy. 1 GWh equals 1,000 MWh. A plant giving 1 GW of power for 6 hours delivers 6 GWh.