Massachusetts-based CFS, a leading fusion energy startup, announced a successful $863 million Series B2 funding round. The investment comes from prominent companies and venture funds, including Google, Nvidia, Breakthrough Energy Ventures, and many international investors.

CEO Bob Mumgaard highlighted the round’s purpose: “It’s not just about fusion as a scientific concept. It’s about making it a commercial reality.” CFS has now raised nearly $3 billion, the highest of any fusion startup.

The company is developing the Sparc prototype, a tokamak reactor expected to begin operations next year, aiming for scientific breakeven in 2027. While Sparc is not designed to sell electricity, it will validate the technology and provide cost data critical for the next step: Arc, the first commercial-scale fusion plant planned for Virginia starting in 2027–2028.