Big Money Flows Into Long-Duration Energy Storage

The 500 MW California storage project secures new equity as it prepares to break ground later this year

16 Mar 2026

The sun shines brightly on the California desert, but the state’s energy problem has always been what happens when it sets. While lithium-ion batteries have dominated the market, they are short-distance runners in a marathon. To keep the lights on for eight hours or more, the grid needs something heavier. Hydrostor, a Canadian firm, believes the answer lies in pumping air into underground caverns. Its Willow Rock project in Kern County aims to provide 500 MW of power, making it a massive test of whether "long-duration" storage can finally move from the laboratory to the balance sheet.

On February 25th, Hatch, an engineering firm, announced an equity stake in the project. It joins a list of heavyweights including Goldman Sachs and the Canada Growth Fund. The timing is notable. While global investment in this sector fell by 30% last year, Willow Rock is moving against the wind. The project recently secured a conditional loan guarantee of $1.76bn from the Department of Energy, the largest of its kind.

The logic is simple: as California retires its gas plants, it needs a way to store renewable energy for days, not just minutes. However, the economics are difficult. Cheap lithium batteries and high interest rates have made many investors wary of massive, long-term infrastructure projects. Hydrostor’s Chief Financial Officer, Beth Summers, noted that the Hatch agreement signals confidence not only in the underlying technology but in the company’s broader commercial trajectory.

To mitigate the risk, the project has secured a "revenue anchor" through an agreement with California Community Power. This provides a guaranteed buyer for a portion of the energy. Success is not certain, but the concentration of capital suggests that for those with deep enough pockets, the "missing link" of the energy transition is worth the price of admission. If Willow Rock breaks ground as planned in 2026, it will prove that storing air is no longer just a lofty ambition. For now, the industry is watching to see if the financial plumbing holds as much pressure as the caverns themselves.