How much funding has Mainspring Energy raised?

Mainspring Energy has raised $933.0M in total funding, most recently a Series F round.

Who are Mainspring Energy's investors?

Mainspring Energy's investors include General Catalyst, Khosla Ventures, DCVC (Data Collab), Amazon Climate Pledge Fund, Temasek, Lightrock.

When was Mainspring Energy founded?

Mainspring Energy was founded in 2010.

Where is Mainspring Energy headquartered?

Mainspring Energy is headquartered in Menlo Park, California, United States.

What industry is Mainspring Energy in?

Mainspring Energy operates in Energy, Climate Tech.

How many employees does Mainspring Energy have?

Mainspring Energy has 51-200 employees.

Mainspring Energy

formerly Mainspring

Flexible, affordable, and low emissions onsite power.

Menlo Park, United States · Founded 2010 · $933.0M raised

Energy

Climate Tech

Headquarters: Menlo Park, California
Employees: 51–200
Founded: 2010
Business Model: B2B

Website: mainspringenergy.com
Total Funding: $933.0M
Last Round: $258.0M Series FApr 2025
Rounds: 4

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 $933.0M in total across 4 rounds, most recently a $258.0M Series F round in Apr 2025. Investors include General Catalyst, Khosla Ventures and DCVC (Data Collab).

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