Fourth Power sells to utilities and power producers plus data centers and other large loads that need firm multi-day capacity. The company points to a market above 200 billion dollars for long-duration storage that fits dense sites.
Its one-gigawatt-hour-per-acre footprint needs no water, fuel, or combustion permits, which suits constrained and urban locations. The business remains pre-commercial, advancing demonstration tracks in Massachusetts toward first-of-a-kind operating systems.
Fourth Power raised a 19 million dollar Series A in December 2023 led by DCVC, with Breakthrough Energy Ventures and the Black Venture Capital Consortium participating. The round followed technical milestones in graphite heat storage and thermophotovoltaic conversion.
The company then raised a 20 million dollar Series A Plus round in September 2025 led by Munich Re Ventures, with DCVC and Breakthrough Energy Ventures continuing. The company reports 45 million dollars raised in total.
