Willow Rock Energy Storage Center

Safe, Reliable, and Clean Long Duration Energy Storage for California

The Willow Rock Energy Storage Center is a 500 megawatt (MW) Advanced Compressed Air Energy Storage (A-CAES) facility that is under advanced development in California. It will be capable of delivering 8+ hours of energy.

Project highlights

500 MW / 4,000 megawatt hours (MWh)
Kern County, California
Renewables Integration, Fossil Fuel Generation Replacement, Transmission Optimization
25-40 full-time equivalent jobs during operation, an estimated peak workforce of 700 jobs during construction, and over $500 million of regional direct and indirect economic impacts.
Project Design Life
50+ years


Electricity Grid
Driving economic growth

With a 50+ year lifetime, the facility will provide a stable revenue source for local communities. A-CAES plants use standard components and enables workers from the fossil-fuel industry to transfer existing skills to the clean energy future.

The project will support diversified wage job opportunities and generate significant regional economic development from both the construction and operation of the project.

Electricity grid benefits

Willow Rock will allow California’s attractive and growing solar and wind resources to be directly converted into reliable, on-demand electricity for the greater Los Angeles region and the broader California grid for decades in the future.

Enabling firm capacity

The project supports the delivery of dispatchable electrical capacity into the Los Angeles Basin and broader California grid, while ensuring reliable long duration storage capacity well into the future as long duration storage becomes increasingly important to reliably serve load.

Delivering transmission system value

Willow Rock, and A-CAES technology, provides value in addition to energy storage by helping optimize the use of the existing transmission system. By storing excess wind and solar energy during times of abundance and dispatching this energy when it is most needed, our system allows for more efficient use of transmission lines to deliver reliable service and ensure new transmission is built where it’s most needed.

Technological diversification

A-CAES technology offers systems diversity to the California grid to help enable grid resilience. It provides different generation characteristics relative to the other grid assets and storage technologies thereby supporting a more robust portfolio of clean energy resources.

Facilitating delivery of renewables

The facility will deliver dispatchable capacity, using renewable energy generation in the High Desert area directly into the LA Basin and enable further renewable asset growth in the High Desert Solar Resource Area and Tehachapi Wind Resource Area.

Supports statewide emission reduction targets

Willow Rock provides an alternative to the use of fossil fuel power plants to meet electricity demand. It will support California’s objective of reducing GHG emissions 40% below 1990 levels by 2030. Key for enabling SB100 and LA100 objectives for 100% carbon-free renewable electricity by 2045.

Minimal land and water requirements

A-CAES offers the equivalent bulk energy storage capabilities as pumped hydro storage with substantially lower land and water requirements. A-CAES is a sustainable energy storage technology that is non-combustible, has minimal residual hazardous waste at asset retirement and will experience virtually no performance degradation over its commercial lifetime.


Support 100% net-zero carbon by 2045 (SB100 & LA100)


Stimulate economic growth and new jobs


Improve grid reliability and help prevent future blackouts


Deploy proven technologies and existing workforce skills

Supporting California’s carbon-free objectives

As California moves towards its objective of achieving 100% carbon-free electricity by 2045, it will require large-scale, long duration storage to fully integrate increasing levels of renewable generation capacity. A-CAES is the solution.