Funding round
Commonwealth Fusion Systems Series B
Commonwealth Fusion Systems, which works in fusion power plant manufacturing and delivery in Harvard, raised $863M in a Series B round announced on 28 Aug 2025. 34 firms took part, 12 of them already investors. It is Commonwealth Fusion Systems' second venture round on record; the one before was a Series A in May 2020.
$863M
Amount raised
Not disclosed
Post-money valuation
34
Investors
no lead named
Valuation
What this round says about the price
Commonwealth Fusion Systems did not disclose a valuation in this round. It came 63 months after Commonwealth Fusion Systems' Series A. It is 44% of the $1.95B Commonwealth Fusion Systems has raised in the venture rounds on record. Commonwealth Fusion Systems raised again 11 months later: a Series C round of $1.00B in Jul 2026.
Investors
Who put money in
34 firms took part; no lead investor was named.
Investors
- Brevan Howard Macro Venture Fund new investor
- Morgan Stanley backs 120 venture-backed companies new investor
- FFA Private Bank (Dubai) Ltd. new investor
- Galaxy backs 113 venture-backed companies new investor
- backs 16 venture-backed companies new investor
- backs 60 venture-backed companies new investor
- backs 21 venture-backed companies new investor
- NVentures (NVIDIA’s venture capital arm) new investor
- backs 10 venture-backed companies new investor
- Woori Venture Partners US new investor
- MITSUI & CO., Ltd. new investor
- Mitsubishi Corp. new investor
- Development Bank of Japan Inc. new investor
- Fujikura Ltd. new investor
- JERA Co., Inc. new investor
- JGC JAPAN CORP. new investor
- Mitsui Fudosan Co., Ltd. new investor
- Mitsui O.S.K. Lines, Ltd. new investor
- NTT Inc. new investor
- Sumitomo Mitsui Banking Corp. new investor
- Sumitomo Mitsui Trust Bank Ltd. new investor
- The Kansai Electric Power Co., Inc. new investor
- Breakthrough Energy backs 113 venture-backed companies existing investor
- Emerson Collective backs 76 venture-backed companies existing investor
- Eni existing investor
- backs 41 venture-backed companies existing investor
- Gates Frontier existing investor
- GV backs 428 venture-backed companies existing investor
- Hostplus Superannuation Fund existing investor
- Khosla Ventures backs 396 venture-backed companies existing investor
- Lowercarbon Capital backs 110 venture-backed companies existing investor
- backs 33 venture-backed companies existing investor
- backs 17 venture-backed companies existing investor
- Tiger Global backs 391 venture-backed companies existing investor
Use of proceeds
What the money is for
According to the announcement, the money goes to product development, scaling operations and working capital.
- Product development
- Scaling operations
- Working capital
Comparable rounds
How it compares
6 Series B rounds in Electric Supplies & Power Generation within a year either side disclosed an amount; the median was $36M, and this round was 24 times the median. The closest in time, other companies' Series B rounds in Electric Supplies & Power Generation:
| Company | Announced | Amount | Post-money | Led by |
|---|---|---|---|---|
| Electric Supplies & Power Generation | 19 Aug 2025 | $100M | not disclosed | Valor |
| Electric Supplies & Power Generation | 20 Jun 2025 | $23M | not disclosed | Eneco Ventures |
| Electric Supplies & Power Generation | 1 Oct 2025 | $14M | not disclosed | not named |
| Electric Supplies & Power Generation | 19 Feb 2026 | $13M | not disclosed | Arizona Nuclear Ventures |
| Electric Supplies & Power Generation | 4 Sep 2024 | $50M | not disclosed | not named |
| Blue Energy Electric Supplies & Power Generation | 16 Jul 2026 | undisclosed | not disclosed | not named |
| Valar Atomics Electric Supplies & Power Generation | 3 Aug 2026 | $1.00B | $6.00B | Sequoia Capital |
Sources
Where this comes from
Reported by 5 sources.
Questions
Frequently asked
How much did Commonwealth Fusion Systems raise in its Series B round?
Commonwealth Fusion Systems raised $863M in its Series B round, announced in Aug 2025.
Which investors took part in Commonwealth Fusion Systems' Series B round?
Brevan Howard Macro Venture Fund, Morgan Stanley, FFA Private Bank (Dubai) Ltd., Galaxy, Gigascale Capital and HOF Capital and 28 more.
What was Commonwealth Fusion Systems' valuation at the Series B round?
It was not disclosed.
How does it compare with other Series B rounds in Electric Supplies & Power Generation?
6 Series B rounds in Electric Supplies & Power Generation within a year either side disclosed an amount; the median was $36M, and this round was 24 times the median.
Did Commonwealth Fusion Systems raise again after this round?
Yes: a Series C round in Jul 2026 of $1.00B.