Mainspring Energy
formerly MainspringFlexible, affordable, and low emissions onsite power.
Menlo Park, United States · Founded 2010 · $643.0M raised
- Headquarters
- Menlo Park, California
- Employees
- 51–200
- Founded
- 2010
- Business Model
- B2B
- Website
- mainspringenergy.com
- Total Funding
- $643.0M
- Last Round
- $258.0M Series FApr 2025
- Rounds
- 3
About
Mainspring Energy is a Menlo Park-based clean energy company that manufactures linear generators — a novel power technology converting fuel directly to electricity through a low-temperature, flameless reaction with near-zero NOx emissions. Founded in 2010 by three Stanford engineers as EtaGen, the company rebranded to Mainspring Energy in 2020 and has raised over $850 million. Its generators serve data centers, utilities, and industrial customers needing flexible, fuel-agnostic onsite power.
Summary
Mainspring Energy is an Energy company based in Menlo Park, United States, founded in 2010. It has raised $643.0M in total across 3 rounds, most recently a $258.0M Series F round in Apr 2025. Investors include General Catalyst, Khosla Ventures and DCVC (Data Collab).
Tech & App Stack
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Funding History
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Apr 2025
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Series D through Series F — per-round amounts, valuations, and who invested in each round.
Investors
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