Energy storage lets renewables provide 24/7 electricity. This guide ranks the main storage technologies by cost, duration, scale, and where each fits. Batteries dominate new deployment but the portfolio picture is richer than headlines suggest.
The storage menu
| Technology | Typical duration | Deployment status |
|---|---|---|
| Lithium ion battery | 1 to 6 hours | Dominant new deployment |
| Pumped hydro storage | 8 to 100+ hours | Largest by installed GW |
| Compressed air (CAES) | 10 to 100 hours | Limited deployment |
| Flow battery | 4 to 12 hours | Emerging commercial |
| Thermal storage | 4 to 12 hours (electric heat), longer for CSP | CSP linked plus emerging electric heat |
| Gravity storage | 4 to 12 hours | Pilot scale |
| Hydrogen | Days to seasons | Pilot to commercial |
| Flywheels | Seconds to minutes | Grid ancillary services |
Lithium ion battery
The fastest growing storage technology. Grid scale lithium ion has fallen 80 percent in cost since 2015. Global installed capacity passed 100 GW in 2024, dominated by California, Australia, China, and Texas. Typical durations are 2 to 4 hours; longer durations are commercially viable but not yet dominant.
Pumped hydro storage
Pumped hydro uses cheap off peak electricity to pump water uphill to an upper reservoir, then generates during peak demand as water flows back down. Global installed capacity is roughly 175 GW, the largest storage technology by capacity. New pumped hydro is limited by suitable topography and permitting.
Compressed air storage
Compressed air energy storage (CAES) compresses air into underground caverns during charging, then expands and heats it to drive a turbine during discharging. Two commercial plants exist (Germany, Alabama). Advanced adiabatic CAES could improve efficiency. Development is slow due to site constraints.
Flow batteries
Flow batteries store energy in liquid electrolytes pumped through electrochemical cells. Vanadium redox is the most mature; iron flow and zinc bromine are emerging. Advantages: long cycle life, deep discharge tolerance, and independent power and energy sizing. Disadvantages: lower energy density than lithium.
Thermal storage
Concentrating solar power (CSP) plants use molten salt for thermal storage. Grid connected electric heat storage (heating rocks, sand, or molten salt with electricity) is emerging as a cheap long duration storage option. Companies like Antora Energy, Rondo Energy, and Kraftblock are commercialising.
Gravity storage
Gravity storage lifts heavy masses (concrete blocks, water) during charging, then generates during discharging. Energy Vault and Gravitricity are notable developers. Commercial deployment is still in early stages.
Hydrogen storage
Green hydrogen produced by electrolysis can be stored in tanks, salt caverns, or pipelines. Ideal for long duration (days to seasons) and hard to abate sector coupling. Round trip efficiency is only 30 to 40 percent, but the potential for very long duration storage is unique. See IEA Global Hydrogen Review 2024.
Cost comparison
| Technology | Typical CAPEX (USD per kWh) | Round trip efficiency |
|---|---|---|
| Lithium ion | 250 to 400 | 85 to 92% |
| Pumped hydro | 150 to 400 | 70 to 85% |
| CAES | 150 to 300 | 50 to 70% |
| Flow battery | 400 to 800 | 65 to 80% |
| Thermal (CSP) | Included in CSP capex | Varies |
| Electric heat storage | 50 to 200 | 60 to 80% |
| Gravity | 150 to 400 | 75 to 85% |
| Hydrogen | Depends heavily on scale | 30 to 40% |
Matching storage to need
| Need | Best fit |
|---|---|
| Frequency response (seconds) | Flywheel, lithium ion |
| Diurnal cycling (hours) | Lithium ion |
| Daily to weekly | Pumped hydro, CAES, flow |
| Seasonal (weeks to months) | Hydrogen, pumped hydro (large reservoir) |
| Behind meter home | Lithium ion |
| Industrial process heat | Thermal storage |
Global installed storage 2025
Where deployment is fastest
California, Texas, and Australia lead battery deployment. China leads pumped hydro deployment. Long duration and hydrogen pilots are concentrated in Europe, US, and Japan.
Material supply chains
Market design
Storage revenues come from energy arbitrage, capacity payments, ancillary services, and increasingly grid stability products. Market designs vary widely across jurisdictions and shape storage economics.
Where the industry is going
- Longer duration lithium ion (4 to 8 hours) as project scale grows.
- Emerging alternative chemistries (sodium ion, iron air).
- Electric heat thermal storage scaling for industrial applications.
- Green hydrogen scaling for hard to abate and long duration.
- Pumped hydro rejuvenation with underground designs.
- Gravity storage commercial deployment.
Frequently asked questions
Are batteries the future of storage?
The near term dominant technology, yes. Long duration needs other options.
Can pumped hydro grow more?
Yes but slowly. Underground designs may unlock new sites.
Is hydrogen storage practical?
For long duration, potentially yes. Low round trip efficiency is the tradeoff.
What about home batteries?
Growing but economics vary by tariff structure. See our companion article on home solar.
Do EVs help grid storage?
Vehicle to grid is emerging. Not mainstream yet but growing.
How long do batteries last?
Grid scale lithium ion 15 to 20 years. Cell degradation 10 to 20 percent capacity loss.
Are alternative chemistries safer?
LFP is safer than NMC. Sodium ion is safer still. Tradeoffs on energy density.
Is compressed air coming back?
Advanced adiabatic CAES might. Limited by site availability.
What about gravity storage?
Interesting but still early. Cost competitiveness against batteries unclear.
What is a duration measure?
Hours of full power output at rated capacity. 2 hour battery discharges rated power for 2 hours.
Summary
Energy storage is a multi technology portfolio. Lithium ion batteries dominate new short duration deployment. Pumped hydro remains the largest by capacity. Long duration options (hydrogen, thermal, gravity) are emerging. Different needs suit different technologies. A well designed low carbon grid uses all of them at different roles. Investment is scaling rapidly but pace still needs to increase to support fully decarbonised grids.
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