Exowatt closed a $50 million funding round in November 2025, led by MVP Ventures and 8090 Industries, extending the company's April 2025 $70 million Series A round to a total of $120 million raised. The startup, backed by Sam Altman and Andreessen Horowitz, is attempting to provide continuous, 24-hour power supply for AI data centres using thermal energy storage at just 1 cent per kilowatt-hour, which is 90% cheaper than average U.S. grid rates. Data centres currently consume approximately 1% of the world's electricity, but AI demand is forecast to push that figure to 3-4% by the end of the decade.
Exowatt's P3 system consists of shipping container-sized modular units that use concentrated solar power to heat specialised bricks to 1,200°C, where energy can be stored in thermal batteries for up to five days. The system uses lenses to focus sunlight, then fans transfer hot air to a Stirling engine that generates electricity. According to Hannan Happi, Exowatt's co-founder and CEO, the company has a backlog of approximately 10 million P3 units representing 90 gigawatt-hours of capacity. The company expects to hit its 1-cent target when production reaches around 1 million units per year, which through economies of scale will enable dramatic cost reductions, similar to how photovoltaic solar panel manufacturing revolutionised the energy industry.
The technology represents a modern reimagining of decades-old concentrated solar power storage solutions that were previously difficult to scale economically. Exowatt's distinction lies in its modular approach and simple manufacturability, which enables mass production, whilst previous thermal solar power projects were typically bespoke, project-specific solutions. The company offers an on-site deployable system directly at data centre locations, thereby eliminating years-long waits for grid interconnection, a critical advantage during rapid AI infrastructure expansion.
Sources
1. https://techcrunch.com/2025/11/13/sam-atlman-backed-exowatt-wants-to-power-ai-data-centers-with-billions-of-hot-rocks/
2. https://www.extremetech.com/energy/exowatt-wants-to-fix-the-ai-power-conundum-with-millions-of-hot-rocks
3. https://www.techbuzz.ai/articles/altman-backed-exowatt-targets-1-kwh-power-with-hot-rock-tech
