Commonwealth Fusion Systems (CFS)
companyCommonwealth Fusion Systems (CFS)
Type: Company — Private fusion startup (spinout of MIT PSFC)
Commonwealth Fusion Systems is the leading private fusion company globally by funding raised and technical credibility. It is building SPARC — a compact tokamak that uses High-Temperature Superconducting (HTS) magnets to achieve the world's highest magnetic field in a fusion device, enabling a much smaller and cheaper machine than ITER. SPARC is the demonstration; ARC is the planned commercial power plant.
Strategic Position
CFS's core innovation is the demonstration of HTS magnets at the required field strength (20 Tesla) — achieved in September 2021, a milestone considered by many fusion scientists to have definitively validated the compact tokamak approach. The SPARC device itself is now under construction at Devens, MA.
Google PPA: CFS signed a 200 MW power purchase agreement with Google for output from the first ARC commercial power plant (expected early 2030s, Virginia). This is the largest and most credible long-term fusion PPA signed.
Funding: $863M Series B2 (disclosed 2023-2024), bringing total to ~$2B+. Nvidia joined as a first-time investor in the B2 round alongside Google, Khosla Ventures, and Bill Gates's Breakthrough Energy Ventures.
Technical Approach
- Technology: Tokamak (magnetic confinement), HTS magnets (REBCO tape)
- Key advantage: 20T magnets allow a ~1.7m plasma radius vs ITER's 6.2m — 40× smaller volume
- SPARC: 8-module machine, 18 HTS magnets; Q > 2 target (net energy gain); first plasma target ~2027
- ARC: Commercial successor; 200 MWe output; Virginia site for Google PPA
Funding & Investors
| Round | Amount | Key Investors |
|---|---|---|
| Series B (2021) | $1.8B | Breakthrough Energy, Google, Khosla, Temasek |
| Series B2 (2023-24) | $863M | Nvidia (new), Google, Khosla, Breakthrough Energy |
Milestones
- Sep 2021: HTS magnet demonstration at 20 Tesla — validated compact tokamak approach
- 2025: SPARC construction begins at Devens, MA
- Early 2026: First of 18 HTS magnets installed in SPARC device; device now 60% complete
- ~2027: First plasma target for SPARC
- 2030s: ARC commercial plant for Google PPA
Outstanding Questions
- Does SPARC achieve Q > 2 on first plasma campaign, or require multiple iterations?
- What is the actual LCOE for ARC electricity? (CFS has not published detailed cost models)
- Can the 2030s ARC timeline hold given SPARC is still in construction in 2026?
- Does Nvidia's investment signal an AI-fusion software collaboration?