Key facts
- Mainspring’s last known valuation is $1.9B (Apr 2025).
- 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).
- ·The complete investor list — 37 names
- ·Watchlist + deal alerts for Mainspring
- ·The full record, as it builds
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.
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)
Mainspring doesn't have a composite mark yet — a PA Mark is published once enough pricing inputs exist (trade prints, fund marks, round prices). The rest of the record below builds toward it.
Recorded secondary trades
No secondary trades in Mainspring shares have been recorded yet. When a print lands — third-party, direct report, or platform — it appears here with structure, source, and price.
Institutional fund marks
No SEC-registered fund has reported a fair-value mark on Mainspring in its N-PORT filings yet. We sweep new filings monthly.