Thermal storage startup Exowatt gets funding injection from Silicon Valley VCs

Exowatt, a U.S.-based renewable energy company, has closed a new $70 million Series A funding round, with funding said to help scale the company’s thermal energy storage solution.

The funding comes seven months after it launched its flagship product, the Exowatt P3. Unveiled at the RE+ conference in September 2024, the modular Exowatt P3 is a dispatchable solar solution, that captures and stores solar thermal energy. This is often known as concentrated solar power or CSP, and the P3 solution can use grid-energy to store heat via resistors, or uses a via lens-based heat collector system to store solar energy as thermal energy or heat in a long-duration battery.

The P3 either supplies heat directly, or converts the stored heat into electricity on demand via a heat engine, with the company claiming in a press release that it is “capable of delivering up to 24 hours of power daily.”

Currently, this is seen as an ideal provider of energy for AI-driven data centers and hyperscalers that require an uninterrupted operation. The P3 can also be connected with or without an interconnection, providing faster scaling of power. Data centers have at times been forced to wait for utilities to strengthen grids, with AI playing a large role in scaling requirements.

In a recent report, the International Energy Agency said in the U.S. alone, power consumption by data centers is “on course to account for almost half of the growth in electricity demand between now and 2030.”

With Exowatt claiming a demand backlog exceeding 90 GWh, the company stated that it is preparing for widespread commercial deployments, which are set to go live in 2025 across several locations in North America. Previously, in 2024, Exowatt had referenced a demand backlog of 1.2 GW.

Few details are known about the type of medium used to store heat, the efficiency of the system, or how the size of the CSP area may require supplying sufficient heat in different locations across the U.S.

Hannan Happi, CEO of Exowatt, recently told pv magazine, “Modular systems are much easier to scale with. We wanted to develop a renewable energy solution to power the rising demand for energy given the most recent AI boom over the last couple of years.

“There is abundant solar energy available and the world is not using it to its full extent,” Happi said when describing the problem that Exowatt was tasked with solving. “The challenge with solar was that it’s not dispatchable, so it’s not really applicable to types of data center loads that are looking for baseload power or very long dispatch cycles.”

The Exowatt P3 can be deployed in 40-foot containers, which is the standard footprint for a shipping container, making it suitable for both small and large-scale commercial and industrial projects. Multiple units can be deployed together in a modular format.

Happi added: “We’ve been overwhelmed with the amount of interest in the P3 since we launched it to market late last year. The additional funding will help us accelerate commercialization and deployment of our solution for the data center energy needs and help us scale our manufacturing capacity as fast as possible to address the almost insatiable demand for power from our customers.”

Exowatt’s $70 million Series A brings the company’s total funding to $90 million to date. The investment was split into equity and debt; each totalling $35 million. Investors in the equity fund led by venture capital firm Felicis include heavyweights including VC firms Andreesen Horowitz, 8090 Industries, Starwood Capital, Thrive Capital, MCJ Collective, MVP Ventures, GOAT VC, and StepStone Group.

The $35 million debt facility is provided by HSBC Innovation Banking and other unnamed lending partners. A debt facility was also established during the seed round for Exowatt in August of 2024.