Mainspring Energy Secures $258M in Funding
Mainspring Energy just landed a hefty $258 million in Series F funding, and it’s not wasting a second putting it to work. The company behind the sleekly named linear generator is scaling up manufacturing, growing its customer base, and expanding its boardroom firepower with two heavyweight industry veterans. This move isn’t just about growth — it’s a loud signal that clean, dispatchable, fuel-flexible power is no longer some theoretical dream. It’s here, and it’s charging full speed ahead.
The round was led by General Catalyst, with deep-pocketed participation from Amazon’s Climate Pledge Fund, DCVC, Temasek, Marunouchi Innovation Partners, M&G Investments, and Pictet Group.
Mainspring’s OG backers like Khosla Ventures, LGT Bank, Gates Frontier, and Lightrock didn’t miss the party either.
Along with the cash injection came two serious additions to Mainspring’s board. Tom Linebarger, former Chairman and CEO of Cummins, and Bethany Mayer, ex-CEO of Ixia and board alum of Sempra, are bringing decades of know-how across energy, infrastructure, and tech.
“I am excited to join the Mainspring Board of Directors at this critical time for energy,” said Linebarger, who’s representing General Catalyst. “The demand for innovative solutions to meet power needs has never been higher, and Mainspring brings a unique and winning solution to the market.”
So what’s got these investors and execs leaning in? Mainspring’s linear generators aren’t your average clean tech.
They’re cost-efficient, super flexible with fuels, and easy to permit just about anywhere.
We're talking scalable power that goes from 250 kW up to 100+ MW, with the bonus of being able to serve everything from EV charging microgrids to cold storage warehouses to wastewater plants.
Basically, it’s like Lego blocks for energy — stack them however you need, plug them in, and go.
Amazon’s clearly a fan. “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 from Amazon’s Climate Pledge Fund. He added, “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.”
And scale they are. Since launching commercial shipments in 2020, Mainspring has racked up hundreds of megawatts in operation and development across a client list that includes some of the world’s largest corporations and utilities. With this new funding round, the company’s total raise now tops $800 million.
“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 founder and CEO 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.”
From grid resiliency to decarbonization goals, Mainspring is betting big that its generator can handle the kind of flexibility today’s energy-hungry world is demanding.
And if this fundraise is any indicator, a lot of smart money is betting right alongside them.
