Mainspring Energy: Funding, Investors & Team (Sep 2026)
Mainspring Energy is engineering advanced technology by developing a prototype of a linear generator that converts fuel to electricity. Mainspring was founded in 2010 by three Stanford engineers- Shannon Miller, Adam Simpson, and Matt Svrcek. Today Mainspring brings together a diverse, talented team of individuals who share the vision to address the growing threat of climate change and the need for affordable electricity for all.
Mainspring Energy has raised $635M across 4 funding rounds on record, the most recent a Series F of $258M announced in Apr 2025.
That round is above the $15M median round size for Energy companies tracked on FundedIQ over the last two years.
Mainspring Energy Company Profile and Key Stats
Latest funding round on record: Apr 2025.
Mainspring Energy Funding Rounds
Mainspring Energy raised $150M in a Series E announced in May 2022.
4 months later, a Series E of $140M was announced in Sep 2022.
2.1 years later, an undisclosed round of $87.0M was announced in Oct 2024.
6 months later, a Series F of $258M was announced in Apr 2025.
Mainspring Energy Founders and Leadership Team
Contact details for the Mainspring Energy team: 1 of 3 have an email address on file.
Start 14-day free trial →Mainspring Energy Funding Compared to Other Energy Startups
Mainspring Energy's latest round of $258M is above the median round in Energy. Medians cover the last 24 months of disclosed rounds.
Funded Startups Like Mainspring Energy in Energy and Menlo Park
Companies Similar to Mainspring Energy
Ampaire is at the forefront of the Third Aviation Revolution, creating aircraft that are…
Thea Energy is taking a faster approach to commercialize fusion energy. The company’s fusion systems will…
Form Energy develops and commercializes a low-cost battery system that can store wind and solar energy for a…
LevelTen Energy is a company that offers a platform for renewable energy buyers, sellers, and advisors to…
Zeno is developing next-generation radioisotope power systems that generate carbon-free, resilient power for…
Base Power is a contemporary energy company that focuses on backup battery systems for homes and electricity…
Valar Atomics is a company focused on scaling nuclear energy beyond the traditional electricity grid.
Antora Energy delivers zero-carbon industrial heat and power to heavy industries that are more reliable than…
Commonwealth Fusion is a research company that develops energy through an inexhaustible power plant. It uses…
Antares Industries is an advanced nuclear energy startup that designs and manufactures adaptable and scalable…
WATT Fuel Cell Corporation is a developer and manufacturer of Solid Oxide Fuel Cell (SOFC) components and…
Gritt Robotics is utilizing AI and Robotics to automate the construction of renewable energy projects.
Mainspring Energy Funding FAQs
What does Mainspring Energy do?
Mainspring Energy is engineering advanced technology by developing a prototype of a linear generator that converts fuel to electricity. Mainspring was founded in 2010 by three Stanford engineers- Shannon Miller, Adam Simpson, and Matt Svrcek. Today Mainspring brings together a diverse, talented team of individuals who share the vision to address the growing threat of climate change and the need for affordable electricity for all.
How much funding has Mainspring Energy raised?
Mainspring Energy has raised $635M across 4 rounds on record. The most recent is a Series F of $258M announced in Apr 2025.
When did Mainspring Energy last raise funding?
Mainspring Energy's most recent funding round on record is a Series F of $258M, announced in Apr 2025.
Who founded Mainspring Energy?
FundedIQ lists Adam Simpson (Founder), Matt Svrcek (Founder) at Mainspring Energy.
Who is the CEO of Mainspring Energy?
Shannon Miller is listed as CEO at Mainspring Energy.
Where is Mainspring Energy headquartered?
Mainspring Energy is based in Menlo Park, California, United States.
How many employees does Mainspring Energy have?
Mainspring Energy is in the 251-500 employee band.
How does Mainspring Energy's funding compare to other Energy startups?
Mainspring Energy's latest round of $258M is above the $15M median round size for Energy companies on FundedIQ across 2,284 tracked companies over the last two years.
About FundedIQ's Mainspring Energy Funding Data
FundedIQ tracks announced funding rounds and refreshes this profile every week. Round dates, stages and amounts are normalised to a single format, converted to US dollars, and de-duplicated: two records of the same round announced days apart are merged, and two genuinely different rounds are kept apart on the amounts they disclose. Amounts shown are the disclosed figures only — a round announced without a number is listed and excluded from the total rather than estimated.
Employee counts are reported bands, not exact headcounts. Founder and executive names carry the job title on record. Anything we do not hold for Mainspring Energy is left off this page rather than filled in.
Know who just raised. Then know who to reach.
Every newly funded startup with its round, its investors and its founders: delivered weekly by email, or searchable in the app.
Alerts from $19/mo · Pro from $99/mo. Card required, nothing charged until day 15, and we email you 3 days before that.