Mainspring key facts
as of Oct 2026- Manufacturer of linear power generators intended to bring affordable, reliable, and net-zero carbon grids of the future.
- Mainspring is valued at approximately $1.9B as of Oct 2026 (last reported valuation).
- It has raised $849.5M; the latest was Later Stage VC ($258.0M) in Apr 2025.
- Notable investors include Alumni Ventures, General Catalyst, Khosla Ventures, U.S. Department of Energy, F-Prime Capital — 37 tracked in total.
- Status: Privately Held (backing).
Mainspring's last reported valuation, Apr 2025. Nothing priced has surfaced since.
- ·The complete investor list: 37 names
- ·Watch Mainspring: the Monday email on marks, rounds and moves
Mainspring funding rounds
No funding rounds for Mainspring are on record yet — either the company hasn't raised institutional capital, or the raise hasn't surfaced in our sources.
Who backs Mainspring
37+Mainspring valuation
Mainspring's last reported valuation was $1.9 billion in Apr 2025. No priced round, secondary trade or fund mark has surfaced since.
Mainspring investors
37 investors are on record for Mainspring, including Alumni Ventures, General Catalyst, Khosla Ventures and U.S. Department of Energy. By type, the record holds 7 venture capital firms and 4 family offices.
About Mainspring
Manufacturer of linear power generators intended to bring affordable, reliable, and net-zero carbon grids of the future. The company's generators use a low-temperature reaction of air and fuel to drive magnets through copper coils to efficiently produce electricity, enabling clients to avail of electricity at a lower cost with higher reliability and lower carbon than the electric grid.
- Sector
- Energy
- HQ
- Menlo Park, CA, United States
- Founded
- 2010
- Employees
- 478
- Website
- mainspringenergy.com/
- Ownership
- Privately Held (backing)
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