Massachusetts-based Commonwealth Fusion Systems (CFS) has raised $863 million in fresh funding from a broad coalition of investors including Nvidia, Google, and Breakthrough Energy Ventures. The raise brings the fusion startup’s total funding to nearly $3 billion, making it the most well-funded company in the sector.
CEO Bob Mumgaard said the round will help accelerate CFS’s mission to make fusion not just a scientific milestone but a commercial industrial reality. The company is building a prototype reactor called Sparc, which is expected to turn on in late 2026 and achieve scientific breakeven by 2027, producing more energy than it consumes.
Though Sparc won’t feed electricity to the grid, it’s a critical step toward CFS’s first commercial power plant, Arc, slated for construction in Virginia around 2027–2028. Both reactors use the tokamak design, leveraging powerful superconducting magnets to confine plasma and unlock near-limitless energy.
Investors in the round include heavyweights such as Tiger Global, Khosla Ventures, Emerson Collective, Gates Frontier, Lowercarbon Capital, and a consortium of 12 Japanese firms led by Mitsui & Co. and Mitsubishi Corporation. Google has already agreed to purchase 200 megawatts from Arc once it comes online.
Related: Libby Adds AI Book Recommendations, Sparking Mixed Reactions
Still, significant hurdles remain. Experts caution that Sparc may uncover new plasma behaviors, and Arc is expected to cost several billion dollars to complete. Mumgaard acknowledged the funding challenge but stressed investor commitment: “It’s also to have the receipts, know what these things cost. We are pretty committed to doing this. And our investors are pretty committed to doing this.”
