Commonwealth Fusion Raises $863M to Advance SPARC and ARC Fusion Projects

Commonwealth Fusion Systems (CFS) raised $863 million in a Series B2 round, marking the largest private capital raise among deep tech and energy companies since its own $1.8 billion Series B in 2021. The round brings total funding for CFS to nearly $3 billion, which represents about one-third of all private investment in fusion companies globally. The company is now positioned as the leader in the race to commercialize fusion energy.

CFS will use the funds to complete SPARC, its demonstration fusion machine under construction in Devens, Massachusetts, and advance its first grid-scale ARC fusion power plant planned for Chesterfield County, Virginia. Google, already a major investor, has agreed to buy half of ARC’s projected power output. The latest funding round attracted a wide range of investors, including Counterpoint Global (Morgan Stanley), NVIDIA’s NVentures, Stanley Druckenmiller, Galaxy Interactive, Planet First Partners, and a consortium of 12 Japanese companies led by Mitsui & Co. and Mitsubishi Corp.

The oversubscribed round drew back existing investors such as Breakthrough Energy Ventures, Eni, Google, Khosla Ventures, Lowercarbon Capital, Emerson Collective, and Tiger Global. CFS highlighted its advances in high-temperature superconducting magnet technology and its accelerated execution on SPARC as key factors in investor confidence. “Investors recognize that CFS is making fusion power a reality. They see that we are executing and delivering on our objectives,” said Bob Mumgaard, CEO and Co-founder of CFS.

• Raised $863 million in Series B2, the largest round in deep tech and energy since 2021

• Nearly $3 billion raised to date, one-third of all private fusion capital worldwide

• Funds to complete SPARC demonstration reactor in Massachusetts and advance ARC power plant in Virginia

• Google agreed to buy half of ARC’s output once operational

• New investors include Counterpoint Global, NVIDIA’s NVentures, Stanley Druckenmiller, Galaxy Interactive, and Japanese consortium led by Mitsui & Mitsubishi

• Existing investors such as Breakthrough Energy Ventures, Eni, Google, and Khosla Ventures expanded their commitments

“Investors recognize that CFS is making fusion power a reality. They see that we are executing and delivering on our objectives,” said Bob Mumgaard, CEO and Co-founder of Commonwealth Fusion Systems.

🌐 Analysis: CFS continues to consolidate its leadership position in fusion by securing nearly one-third of the global private investment in the sector. With SPARC nearing completion and ARC moving forward in Virginia, CFS stands apart from rival startups such as Helion and TAE Technologies, both of which are also raising large rounds. The involvement of global industrial players and major financial institutions underscores growing conviction that fusion may play a role in meeting surging demand for electricity, particularly as AI data centers accelerate energy use worldwide.

🌐 Analysis: CFS’ raise comes amid a surge of nuclear-related investment activity that Converge Digest has tracked throughout 2025. Beyond fusion, multiple fission-based projects are advancing in parallel — including Kairos Power’s Hermes 2 molten salt reactor in Tennessee, Equinix’s partnership with Radiant on micro-reactors, and Microsoft-linked efforts around nuclear-powered cloud campuses. We’ve also reported on U.S. and European moves to tie small modular reactors (SMRs) directly to hyperscale and sovereign AI data centers, as operators seek stable carbon-free baseload capacity to counter the grid stress from large-scale AI clusters. This broader nuclear momentum — both fusion and fission — reflects growing recognition that data center growth will require clean, on-demand gigawatt-scale power.

🌐 We’re tracking the latest developments in nuclear energy for data centers. Follow our ongoing coverage at: https://convergedigest.com/tag/nuclear/