Commonwealth Fusion Systems (CFS) has announced roughly $1 billion in new funding, bringing its total raised to about $4 billion since founding. This is the largest single fusion funding round since CFS's $1.8 billion Series B in 2021.

CFS says the round is anchored by patient, long-horizon capital: sovereign wealth funds, pension funds, and infrastructure and industrial partners, rather than the venture capital behind its earlier rounds, a shift it attributes to the progress of SPARC, its demonstration tokamak. CEO Bob Mumgaard puts SPARC at roughly 80 percent built, with construction expected to finish in early to mid 2027.

Half of the toroidal metal vacuum vessel is hoisted within the white walls of the tokamak hall as technicians watch the lift. The other half sits in the background. Commonwealth Fusion Systems moves the second half of the SPARC vacuum vessel within the tokamak hall.

Turning toward ARC

CFS is directing the new capital entirely to ARC, its first commercial power plant: system prototypes, supply chain and manufacturing retooling, site preparation, and contracting sites for future plants. ARC is in permitting, with Dominion Energy engaged on the Virginia site and a new physics basis published for the plant. The infrastructure investors, the company says, are drawn by the projects they could eventually participate in. The $1 billion will not fully fund ARC, which CFS places in the billion-dollar range rather than the tens of billions.