Commonwealth Fusion Systems company profile: valuation, funding & revenue

This Commonwealth Fusion Systems company profile covers the company's valuation, revenue, funding rounds, investors and history. Commonwealth Fusion Systems works in climate and energy technology, with a focus on fusion power. It was founded in 2018 and is headquartered in Devens, Massachusetts, United States. Every figure links to a public source, and anything the company hasn't disclosed is marked as such.

Revenue

Funding history

Commonwealth Fusion Systems timeline

Key dates from the sources on this page, oldest first. Metric snapshots are listed after the funding events.

• 2018 — Commonwealth Fusion Systems is founded in Devens by Bob Mumgaard (CEO), Dennis Whyte, Brandon Sorbom, Dan Brunner, Martin Greenwald and Zach Hartwig, among others.
• 2021 — Series B: US$1.8B.
• Jul 2026 — Equity round: US$1B.
• July 2026 — Total funding: About US$4 billion.
• July 2026 — Commercial plant: ARC plant planned in Virginia, expected to be complete in the mid-2030s.

Investors

Overview

Commonwealth Fusion Systems, usually called CFS, is trying to build the first commercial fusion power plants. Fusion is the process that powers the sun: fusing light atoms releases enormous energy, with no carbon emissions and far less long-lived radioactive waste than nuclear fission. Scientists have pursued fusion power for decades; CFS's bet is that a new generation of very strong magnets makes it possible to build smaller, cheaper fusion machines much sooner than traditional designs.

CFS was spun out of the Massachusetts Institute of Technology's Plasma Science and Fusion Center in 2018. Its founders include Bob Mumgaard, the CEO, Dennis Whyte, Brandon Sorbom, Dan Brunner, Martin Greenwald and Zach Hartwig. It is based in Devens, Massachusetts, where it is building its demonstration machine, and has grown into the best-funded private fusion company in the world.

The technology

CFS's design is a tokamak, a doughnut-shaped machine that uses magnetic fields to confine plasma heated to over 100 million degrees Celsius. The breakthrough is its high-temperature superconducting magnets, made with a material called REBCO tape, which can produce much stronger magnetic fields than older superconductors. Stronger fields mean the plasma can be confined in a smaller machine, which reduces cost and construction time. In 2021, CFS and MIT demonstrated a large magnet of this type reaching a record magnetic field strength for its kind, a key milestone.

SPARC and ARC

• SPARC: a demonstration machine under construction in Devens, designed to produce more energy from fusion than is used to heat the plasma (known as Q greater than 1). Reports in 2026 said it was expected to come online around 2027.
• ARC: the first commercial power plant, planned for Chesterfield County in Virginia, designed to produce about 400 megawatts of electricity, with completion expected in the 2030s.

Google agreed in 2025 to buy power from the ARC plant, and Italian energy company Eni, a long-time investor, also signed an agreement to buy power from it. Those agreements show that large energy buyers take the project seriously, though they depend on ARC actually being built and working.

Funding

CFS has raised about US$4 billion in total. Its 2021 Series B of about US$1.8 billion remains one of the largest private funding rounds in fusion. In August 2025, it raised a further round of more than US$800 million. In July 2026 it announced US$1 billion in new funding to finish SPARC and plan ARC. CEO Bob Mumgaard declined to name the investors or disclose the valuation. Over the years, its backers have included Breakthrough Energy Ventures (backed by Bill Gates), Eni, Google, Tiger Global and Temasek, among many others. CFS has said it will need to raise billions more to build ARC.

Revenue

CFS has no meaningful revenue from power sales yet. It earns some income from selling its magnet technology and from government research programmes, but its value depends on making fusion work commercially. We show both valuation and revenue as not disclosed.

Competition

CFS competes with other private fusion companies pursuing different approaches, including Helion Energy (which has a power purchase agreement with Microsoft), TAE Technologies, General Fusion in Canada, Tokamak Energy in the UK, and many others. It also competes indirectly with other clean power sources, such as advanced nuclear fission, solar, wind with storage, and geothermal. Its advantages are its funding, its well-proven tokamak approach and its magnet technology.

CFS at a glance

Commonwealth Fusion Systems is a Devens, Massachusetts fusion company spun out of MIT in 2018, led by CEO Bob Mumgaard. It has raised about US$4 billion, including US$1 billion announced in July 2026, without disclosing a valuation. It is building the SPARC demonstration machine, expected to come online around 2027, and plans the 400-megawatt ARC power plant in Virginia.

Why AI is boosting interest in fusion

Technology companies need vast amounts of clean electricity for AI data centres, and they want firm power that runs around the clock, not just when the sun shines or the wind blows. That has made them enthusiastic buyers of future nuclear and fusion power. Google's agreement with CFS and Microsoft's with Helion are examples. For fusion companies, these deals help with fundraising, because they show potential demand for the power at commercially meaningful prices.

The risks are large

• Physics: SPARC must actually achieve net energy gain, which no commercial-scale machine has done.
• Engineering: even with net gain, turning fusion into a reliable power plant involves unsolved challenges, such as materials that withstand intense neutron bombardment and producing tritium fuel.
• Cost and timing: fusion projects have historically run late and over budget.
• Capital: billions more will be needed before any revenue from power sales.

Government programmes can help fill funding gaps; our guide to non-dilutive funding covers how grants and public programmes support deep tech companies.

How investors think about fusion

Valuing a company like CFS is less about current numbers and more about the probability that it reaches each milestone, the cost to get there, and the size of the market if it succeeds. Clean, firm power at scale would be extraordinarily valuable, so even a modest chance of success can justify large investments. Our guide to pre-revenue valuation methods explains these approaches.

Milestones ahead

The biggest milestone is SPARC's first plasma and then net energy gain. After that, watch for ARC construction, new power purchase agreements, further fundraising and government support.

Independent reviews from the scientific community and public results from SPARC will be the most reliable guide to real progress over the next few years.

Latest developments (October 2026)

Commonwealth Fusion Systems has continued building SPARC, its demonstration tokamak in Massachusetts. In January 2026 it installed the first of 18 high-temperature superconducting magnets, and by April it said the facility was about 75% complete, according to the company's blog. It also announced work with Nvidia and Siemens on a digital twin of SPARC. Its August 2025 Series B2 of US$863 million brought total funding to close to US$3 billion. The first ARC power plant is planned for Virginia in the early 2030s.

Takeaways

Utilities and large energy buyers may want to follow fusion developments as part of long-term planning. Climate tech founders can learn from how CFS combined university research with private capital. Investors should treat fusion as a long-term, high-risk, high-reward bet.

Sources

Every figure on this page comes from the public sources below. Where sources disagreed, we used the company's own announcement or a primary news report. Private-company data changes; check the date beside each figure.

1. The Boston Globe