Mainspring Secures $258 Million in Financing to Scale Linear Generator Business; Adds Energy and Tech Leaders to Board

MENLO PARK, Calif., April 14, 2025 /PRNewswire/ -- Mainspring Energy Inc. announced today that it has secured $258 Million in a Series F financing round to expand the company's linear generator power business and operations as it grows in both manufacturing and customer sales. The company also has added two Board members with deep energy and tech industry operating experience – Tom Linebarger, former Chairman and CEO of global power solutions leader Cummins, and Bethany Mayer, former CEO of public technology company Ixia and former Board member of energy infrastructure giant Sempra.

Global investment and transformation company General Catalyst led the raise, joined by Amazon's Climate Pledge Fund, DCVC, Temasek, Marunouchi Innovation Partners, M&G Investments, Pictet Group, and Mainspring's earlier investors including Lightrock and LGT Bank, Khosla Ventures, and Gates Frontier, among others.

Mainspring Linear Generators deliver significant advantages in cost, reliability, and flexibility, including the ability to dynamically switch among fuels. The products are also fully dispatchable, and their low emissions make them easily sited and permitted anywhere. They are scalable from a single unit to a grid-level array, delivering from 250 kW to 100+ MW of power in any increment needed. The product is easily manufacturable and can scale to meet growing power needs.

This combination of flexibility benefits gives customers unmatched optionality in power deployment and has led to the products' rapid adoption in segments as diverse as data centers, EV charging microgrids, commercial buildings, residential developments, cold storage facilities, hospitals, and wastewater treatment plants.

"I am excited to join the Mainspring Board of Directors at this critical time for energy," said Linebarger. "The demand for innovative solutions to meet power needs has never been higher, and Mainspring brings a unique and winning solution to the market."

"Mainspring's linear generator technology has the potential to accelerate the future of low-carbon energy and support a more resilient electric grid – two important goals for Amazon as we work to become net-zero carbon across our operations by 2040," said Thomas Selby, corporate development manager with Amazon's Climate Pledge Fund. "We are excited to collaborate with the talented team at Mainspring as they work to scale their business to meet growing energy demands for new and existing customers."

The two new Mainspring Board members bring valuable operational knowledge and expertise in the power generation and hardware industries. Linebarger, who will be joining the Board on behalf of General Catalyst, is the former Chairman and CEO of global power leader Cummins Inc.  Previously he served as SVP at GE Capital, Chair of the U.S.-China Business Council, and in other corporate leadership roles. Mayer is an experienced public company executive, CEO, and board member with roles at leading corporations including Sempra, Box, HP, Cisco, Apple, and various startups.

"Mainspring is fortunate to have the support of many of the top energy investors in the world, with a strong international perspective, as we prepare for our next phase of growth," said Mainspring CEO and Founder Shannon Miller.  "This round, along with the growth of our Board, strengthens our capacity to deliver more power – faster and at scale – around the world. It also positions us to advance U.S. leadership in innovative power technology and bolster national energy security."

About Mainspring

Mainspring Energy began commercial shipments of its innovative linear generator products in 2020 and today has hundreds of megawatts in field operations and advanced development for leading Fortune 500 companies and utilities. With this latest round of financing, Mainspring has secured more than $800 million in financing to advance its goals in delivering innovative power generation to meet growing global demand. Learn more at mainspringenergy.com.

SOURCE Mainspring Energy, Inc.