Mainspring Energy develops linear generator power products that are fully dispatchable, low‑emission, fuel‑flexible, and scalable from 250 kW to 100+ MW. The units are designed for easy siting and permitting, and the company says the products are easily manufacturable and can scale from single units to grid‑level arrays. Mainspring reports commercial shipments began in 2020 and that it currently has hundreds of megawatts in field operations and advanced development for Fortune 500 companies and utilities. Its technology has been adopted across data centers, EV charging microgrids, commercial buildings, residential developments, cold storage, hospitals, and wastewater treatment plants. The company plans to use new financing to expand manufacturing, grow customer sales, and scale its linear generator business globally. With low emissions and fuel flexibility, Mainspring positions its product to support resilient, low‑carbon power deployment. Mainspring Energy develops and sells linear generators that produce low- or zero-carbon electricity for commercial, industrial, datacenter and utility customers. The company is led by CEO Shannon Miller and counts customers such as Kroger, Lineage Logistics, PG&E and Florida Power & Light. Mainspring’s products are fuel-flexible and intended to increase energy resilience, reduce costs, and help customers meet sustainability goals. The company plans to use the new funding to develop new linear generator models and to accelerate commercial and utility adoption. It also announced a commercial agreement with Lineage Logistics to deploy up to 150 units across Lineage’s U.S. distribution facilities and to explore deployments outside the U.S. and the use of 100% green fuels. Mainspring Energy develops the Mainspring Linear Generator, an onsite, dispatchable, fuel‑flexible power generator that can run on conventional fuels and 100% renewable fuels. The company shipped its first product in mid‑2020 and has pursued deployments across commercial, industrial, microgrid, and utility customers, including big‑box retail, grocery, logistics, telecommunications, agriculture, wastewater treatment, and Fortune 500 utilities. Mainspring recently secured a $150 million unit purchase and project finance agreement with NextEra Energy Resources to promote deployment and renewable fuels adoption. The company plans to use new financing to scale U.S. customer deployments, expand manufacturing operations, and grow staff by more than 50%. Mainspring positions its technology as dispatchable and low‑cost, intended to enable greater use of solar and wind while reducing carbon and improving resilience. Guidehouse Insights is cited on the large market opportunity for distributed generation, estimated at $86 billion in 2020 and $212 billion by 2030. Mainspring is based in Menlo Park, Calif., and is backed by venture, strategic, and financial investors. EtaGen produces linear generators that use a low-temperature reaction of air and natural gas to drive magnets through copper coils and generate electricity. The company targets onsite electric power for commercial customers across industries such as utilities, grocery, banking, logistics, retail and telecom. EtaGen plans installations with customers in those industries and will use new funding to scale manufacturing and operations. The financing will also support expansion of its sales, marketing, and service teams. EtaGen is led by CEO Shannon Miller and was founded in 2010.

Total raised

$586M

Funding rounds

4

Latest round

Series F

Latest activity

Apr 2025