This article was written by Jeffrey Jones and was published in the Globe & Mail on December 24, 2025.
Energy storage developer Hydrostor Inc. is close to breaking ground on its first utility-scale project after receiving final regulatory approval in California.
Toronto-based Hydrostor said it is finalizing offtake agreements with utilities in the state before starting construction at its US$1.5-billion Willow Rock Energy Storage Center in Kern County, Calif., north of Los Angeles.
The U.S. project, which has been under review for more than four years, is one of two large developments the company expects to start in 2026. The other is in New South Wales, Australia.
Its long-duration technology, known as advanced compressed air energy storage, is designed to smooth out electricity supply on power grids, storing excess power generated from fast-growing renewable sources such as wind and solar until it’s needed.
Hydrostor’s system works by pumping compressed air into a cavern deep underground. The rush of air pushes water up to a reservoir at the surface. When electricity is needed, the water is released back into the cavern, sending the air out and driving turbines to generate power.
The benefits are that the facility can store energy for longer periods than batteries, and the system can run on either excess or off-peak power from the grid or from renewable sources.
Last Friday, the California Energy Commission granted final permitting approval to the 500megawatt/4,000-megawatt-hour project, which will have the capacity to power more than 400,000 homes for more than eight hours at a time.
Hydrostor president Jon Norman said the company has grid interconnection agreements for its planned facility, as well as engineering, procurement and construction contracts, and union deals, in place.
“That’s good to start constructing the project. We just need those last pieces of revenue,” Mr. Norman said. Early this year, the project won conditional approval from the U.S. Department of Energy for a loan guarantee of up to US$1.76-billion. However, since then, U.S. President Donald Trump has cancelled many green and climatefriendly programs.
The company said, based on its discussions with the department, that it is confident its financing is secure. It offers benefits to U.S. utility customers, and “grid reliability and resilience are bipartisan priorities,” chief executive Curtis VanWalleghem said in a statement Tuesday.
In February, Hydrostor secured US$200-million in financing from the Canada Growth Fund, Goldman Sachs and the Canada Pension Plan Investment Board to push forward with its projects. Its other investors include ArcTern Ventures, Loren Partners and Canoe Financial.
The company plans to have the Willow Rock project in operation in five years. Mr. Norman said there is more opportunity on the horizon, as California has called for a major expansion of storage capacity by 2032.
In Australia, Hydrostor is nearing the start of construction on a 200-megawatt/1,600-megawatt-hour project in Broken Hill, New South Wales, which is estimated to cost about US$640-million.
Mr. Norman said its proposal has been delayed for regulatory reasons – its planned method of storing and transmitting power is a first for the country.
Those details, as well as sales contracts, are being finalized. “We expect to have an announcement early in the year about a priority designation for that project from the New South Wales government that will form a very strong basis for it to go forward,” Mr. Norman said. “So we’re really looking at getting to construction on these projects in parallel.”
In total, the company says it has the potential to develop 7,000 megawatts’ worth of projects in the next few years in Canada, the U.S., Australia and Britain.
Hydrostor plans to construct some of them itself, but also sell the systems to utilities and independent power producers that can operate them on a turnkey basis, Mr. Norman said.
“So this really is the beachhead for an entire growth industry around compressed air energy storage,” he said.