Hydrostor’s Willow Rock Storage Project Wins Final Power Plant License Approval
Hydrostor, a global leader in long-duration energy storage (LDES) solutions, has achieved a major regulatory milestone with the Willow Rock Energy Storage Center securing final permitting approval from the California Energy Commission (CEC). This approval positions the landmark project to be fully shovel-ready by 2026 and marks a significant step forward in California’s efforts to modernize its electricity grid, integrate higher levels of renewable energy, and meet rapidly increasing power demand driven by electrification, data centers, and artificial intelligence applications.
The Willow Rock Energy Storage Center is a 500-megawatt (MW), 4,000-megawatt-hour (MWh) advanced compressed air energy storage (A-CAES) facility. Designed to deliver eight hours of continuous discharge to the grid, the project will play a critical role in providing grid reliability, resiliency, and long-duration capacity during periods of peak demand or when renewable generation is unavailable. Once operational, it will rank among the largest long-duration energy storage facilities in the United States.
Hydrostor Co-Founder and Chief Executive Officer Curtis VanWalleghem emphasized the importance of the CEC’s decision, describing it as a foundational moment not only for the Willow Rock project but also for the company’s broader growth strategy in North America. He noted that receiving the permit unlocks the next phase of development for Hydrostor’s multi-gigawatt pipeline across the continent.
According to VanWalleghem, advanced compressed air energy storage will be essential to meeting the next wave of electricity demand growth, much of which is being fueled by energy-intensive sectors such as data centers and AI infrastructure. At the same time, he stressed that grid solutions must maintain affordability and reliability for existing customers. Hydrostor’s A-CAES technology, he said, is uniquely positioned to balance these priorities by providing large-scale, long-duration storage without the limitations associated with short-duration battery systems.
Hydrostor President Jon Norman echoed these sentiments, highlighting the collaborative effort that made the permitting process successful. He expressed gratitude to the California Energy Commission commissioners and staff, as well as to community stakeholders and local leaders, for their engagement and support throughout the review process. Norman emphasized that the Willow Rock Energy Storage Center will serve as a major economic engine for Kern County and the surrounding region.
With permitting now complete, Hydrostor is preparing to move forward with construction planning and workforce mobilization. The project is expected to create thousands of jobs during the construction phase, delivering significant short-term economic benefits to East Kern County and the greater Antelope Valley. Over its projected 50-year operational lifespan, the facility will support approximately 40 permanent, high-quality jobs, contributing to long-term regional economic stability.
Strategically located in Kern County, the Willow Rock Energy Storage Center will use Hydrostor’s proprietary A-CAES technology to store surplus electricity when supply exceeds demand—such as during periods of high solar or wind generation—and then release that energy during peak usage hours. This capability is especially valuable in California, where solar generation is abundant during daytime hours but demand often peaks in the evening when solar output declines.
At full operation, the Willow Rock facility will be capable of supplying electricity to more than 400,000 homes for over eight hours, providing a critical buffer against grid stress events, heat waves, and supply shortfalls. By offering sustained, dispatchable power, the project will help reduce reliance on fossil-fuel-based peaker plants and support California’s long-term decarbonization goals.
In addition to its energy reliability benefits, the project represents a substantial financial investment in the region. Hydrostor estimates that Willow Rock will bring more than $500 million in direct investment to East Kern County and the Antelope Valley. This investment is expected to generate secondary economic activity through local suppliers, contractors, and service providers, amplifying the project’s overall economic impact.
Local government support has played a key role in advancing the project. In early December, the Willow Rock Energy Storage Center received its franchise agreement from the Kern County Board of Supervisors. Earlier in the year, in April, the Board also issued a conditional letter of support, signaling strong alignment between Hydrostor’s project objectives and the county’s economic development and energy resilience priorities.
The Willow Rock project holds particular significance for Hydrostor as it represents the company’s first utility-scale energy storage facility to be built in the United States. While Hydrostor has already established a global footprint, this project marks a major expansion of its presence in the U.S. market and sets the stage for future large-scale deployments of A-CAES technology nationwide.
Beyond California, Hydrostor is advancing a diversified portfolio of projects around the world. The company is currently developing another late-stage A-CAES project in New South Wales, Australia, and maintains a global development pipeline totaling approximately 7 gigawatts (GW). This pipeline spans multiple regions, including the United States, Australia, Canada, and the United Kingdom, reflecting growing international demand for long-duration storage solutions capable of supporting high-renewables power systems.
As power systems continue to evolve, long-duration energy storage is increasingly viewed as a cornerstone technology for enabling deep decarbonization while maintaining grid stability. With final permitting secured for Willow Rock, Hydrostor is now poised to demonstrate at scale how advanced compressed air energy storage can deliver reliable, affordable, and resilient power for decades to come.
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