Commonwealth Fusion Systems, a Massachusetts-based fusion energy startup, has announced a $863 million Series B2 funding round. Notable investors include Nvidia, Google, Breakthrough Energy Ventures, and a consortium of global institutions.
CEO Bob Mumgaard emphasized the purpose of the round: “We’re not just funding fusion research. We’re asking how to make fusion commercially viable on an industrial scale.” To date, CFS has raised nearly $3 billion, more than any other startup in the fusion sector.
CFS is developing the Sparc prototype reactor, a tokamak designed to demonstrate net energy gain. Sparc is expected to turn on in 2026, with scientific breakeven projected for 2027. While Sparc will not provide power to the grid, it is essential for validating technology, estimating costs, and training the team for future projects.
If Sparc succeeds, construction of Arc, CFS’s commercial-scale fusion plant in Virginia, will likely begin in 2027–2028. The company has already secured a preliminary deal with Google to purchase 200 megawatts of power from Arc.
