Commonwealth Fusion Systems raises $1B to commercialize fusion power

Commonwealth Fusion Systems raised $1 billion in a new funding round on July 30, 2026.

The round included institutional investors such as pension funds, sovereign wealth funds, and industrial partners, though CFS did not name the specific investors.

This brings the startup's total funding to $4 billion. The new capital will support commercialization as CFS builds its Sparc demonstration reactor and finalizes the design of its Arc commercial power plant.

CEO Bob Mumgaard has indicated the company will continue to raise more capital.

CFS is pursuing magnetic confinement fusion, using powerful magnetic fields to confine plasma and spark reactions. The heat released will power a steam turbine.

The company expects Sparc to achieve scientific breakeven in 2027. That milestone means the reactor produces more energy than it consumes, though not yet enough for grid electricity.

Only one device, at Lawrence Livermore National Laboratory's National Ignition Facility, has reached this point so far.

The Arc plant planned for Virginia has secured purchase commitments. Eni will buy over $1 billion worth of electricity, and Google committed to 200 megawatts, half of Arc's output.

This is CFS's largest round since a $1.8 billion raise in 2021. The company's previous fundraise, an $863 million round, included investors Nvidia, Google, Khosla Ventures, and Breakthrough Energy Ventures.

CFS has not disclosed the costs of Sparc or Arc, though former Virginia Governor Glenn Youngkin said in 2024 that Arc would be a multi-billion-dollar plant.