The POWER Interview: Mainspring Looks to Make Linear Generators Mainstream

The drive to produce more energy by finding new ways to generate power has spurred several innovations. Many companies are studying ways to produce and provide electricity outside of the traditional power grid. Mainspring Energy is among the groups working on solutions for customers who need power sooner rather than later, those who can’t wait for grid connections and also need flexibility and adaptability when it comes to their power supply. Mainspring, headquartered in Menlo Park, California, has spent more than a decade commercializing a new kind of power generator that the company has said can deploy locally, run on virtually any fuel, and deliver reliable, low-emission power. Mainspring Energy’s linear generator produces electricity from natural gas and other fuels using a flameless, low-temperature oxidation reaction rather than traditional combustion. The company said its process moves magnets through copper coils to create power. It eliminates the need for lubricating oil, lowers nitrogen oxide (NOx) emissions, and offers the ability to dynamically switch among fuels. The company has touted its technology as particularly timely in the current market for energy, as power demand from data centers and artificial intelligence (AI) strains the power grid, and industries look for new ways to produce electricity. Tom Linebarger, former chairman and CEO of Cummins, in June of this year took on the role of CEO at Mainspring. Linebarger joined Mainspring’s board in 2025 after retiring from Cummins in 2023. He had spent 30 years at Cummins, where he led the growth strategy for the company’s flagship engine products while expanding into battery electric powertrains and moving into the data center power industry. He previously chaired the Hydrogen Council, a global CEO-led group supporting the hydrogen economy. Linebarger also was a senior advisor focused on energy at General Catalyst, a venture capital and investment company, and also served as a senior advisor for McKinsey and Company, a global management consulting firm. Linebarger provided POWER with insight about Mainspring and why the time is right for adoption of linear generator technology. POWER: You spent 30 years at Cummins. During that time, you navigated some massive market shifts in the energy sector. What about that experience led you to want to join Mainspring? Linebarger: I have a passion for finding new ways to provide abundant, clean, low-cost energy because it is one of the most important ways to improve the lives of people everywhere. Energy is arguably the most important economic driver after human effort and ingenuity. When I looked at what Shannon Miller (founding CEO of Mainspring who started the company in 2010) and the team had built at Mainspring, what struck me was not only the technology itself, though that is genuinely impressive. It was the fact that it works today, in the field, and at rapidly growing scale with real customers who depend on it every day. Not only has Mainspring developed and commercialized the best power generation technology in half a century, it also has a culture of innovation and teamwork which feels like home to me. I came to Mainspring because I want to be part of bringing this solution to the world and I want to do it with this team. POWER: What do you want to accomplish in your role as Mainspring’s CEO? Linebarger: I feel that my life’s purpose is to solve important problems with people that I care deeply about. Mainspring is a company committed to a similar purpose. The power industry is facing some of the most pressing problems it has faced in decades. We are here to help our customers address those challenges, today and for the long haul. Mainspring has a proven technology, a strong customer base, and a market that is growing faster than most people anticipated even a year ago. My job is to make sure the company is built to meet that demand at scale. That means the right team, the right partnerships, and the operational infrastructure and financing to grow significantly while continuing to deliver reliably for every customer we serve. POWER: What’s your view of the scale of challenges facing the energy sector at the moment? How can Mainspring’s linear generators help solve some of these issues? Linebarger: The need to unlock new (generation) capacity is crucial. Electric utilities understand this and are adding capacity and resilience, integrating renewables and batteries, and innovating to manage the increasing complexity. The Edison Electric Institute projects that investor-owned utilities will spend $1.1 trillion between 2025 and 2029 to meet the skyrocketing demand for electricity. Four days. Two conferences. One venue in Washington, D.C., where energy policy, grid decisions, and digital infrastructure converge. In spite of this, the combination of aging infrastructure, transmission and distribution bottlenecks, and new demand calls for more new, firm capacity over the upcoming decade than the grid can deliver on its own. There will be tremendous growth in onsite, behind-the-meter (BTM) power as well. A recent SemiAnalysis newsletter predicted BTM generation will power well over half of new U.S. data centers in 2028+, and the total addressable market for BTM equipment will exceed 50 gigawatts per year by 2029. Mainspring can help on both fronts. Our products deploy in months, run on virtually any fuel, and operate without a grid connection from day one. When the grid eventually arrives, the generator connects and the customer gets the best of both. The grid becomes more valuable, not less, because the customer is already there and ready to integrate into it. In addition, it can deliver energy, reactive power, and ancillary services, giving utilities a single resource that supports both reliability and grid stability as they integrate more variable generation. Affordability is the other pressure point. How do we build a low-cost, reliable, and clean grid of the future? Firm, flexible capacity is the answer. Linear generators can start and ramp fast enough to balance today’s renewables and enable further deployment while improving reliability. They offer energy at the cost and efficiency of much larger generators. And as more data centers connect to the grid, linear generators also offer a solution beyond bridge power: flexible on-site generation can turn data centers’ enormous demand burden into load that can respond to grid conditions. That translates into less price volatility, support to the grid when it needs it, and lower costs for ratepayers. POWER: How exactly does a linear generator work? How does it compare to a traditional generator in terms of efficiency, reliability, maintenance, and cost? Linebarger: A conventional generator burns fuel to create motion and then converts motion into electricity, through combustion, rotating shafts, and complex mechanical assemblies running at high temperatures. A linear generator eliminates most of that. Fuel reacts with air in a low-temperature process and converts directly into electricity. No flame, no turbine, no crankshaft. Because the reaction happens at low temperatures, nitrogen oxide emissions are essentially eliminated, which matters enormously for local air quality and for permitting in areas with stringent air quality standards. Fewer moving parts means a simpler maintenance profile and lower O&M (operations and maintenance) cost. It runs on natural gas, biogas, hydrogen, propane, or virtually any blend, and switches between fuels as supply changes. I’ve looked at a lot of new generator designs over my career. This is the first one I have seen that offers meaningful advantages over existing technologies across multiple dimensions. POWER: What impact will the increased demand for power for data centers, onshoring and electrification have on the energy sector over the next decade? Will we see more distributed generation? Linebarger: The scale of what is being built right now is unlike anything I saw at Cummins, and I watched that company grow through some very significant cycles. A single large AI data center consumes as much electricity as a city of 80,000 people, and companies are building hundreds of them simultaneously. Distributed generation has the potential to grow substantially. Many customers are looking at distributed generation because the interconnection queue is not clearing fast enough to meet that demand through centralized expansion alone. The utilities I talk to understand this. The most forward-thinking ones are already planning for a future where distributed generation and the grid work together as a system rather than competing. POWER: Interconnection queues are a huge bottleneck, pushing many large customers to onsite power projects, even if just temporarily. What changes might we see when the grid interconnection eventually comes through? Linebarger: Most onsite customers understand that some percentage of the large-scale generation projects they build today will be connected to the utility grid eventually—even if that’s 5 to 10 years from now. When the grid connection arrives, it adds resilience and commercial flexibility that on-site generation alone cannot provide. So they are thinking about not only how they can get firm, reliable power now, but how they can build in flexibility that gives them competitive advantages after the connection arrives—the ability to buy power when grid prices are favorable, sell back when demand is high, take advantage of peak-load shaving, and stay online when the grid goes down. The onsite power becomes the foundation of a more sophisticated energy management system. The companies that design for that integrated future from the beginning will have a tremendous advantage over those left with stranded assets. POWER: How do you manage the confidence issue of being a relatively new technology competing with established incumbent technologies? Linebarger: You earn trust by delivering, and then you protect it by continuing to deliver. Mainspring is in commercial operations with large and demanding customers across the country. Those customers chose Mainspring and continue expanding their engagement with us because we delivered on our commitments. We’ve accumulated over 150 years of core operating hours and validated our design under real-world conditions. Every megawatt we put in the ground with a satisfied customer is our evidence. You build confidence one project at a time. POWER: What do you think the energy landscape will look like in 10 years? Linebarger: More generation, more interest in generation that is distributed, affordable, flexible, and cleaner. The grid will be larger and smarter. Onsite generation will be standard for large facilities rather than an exception. The fuel mix is shifting as lower carbon fuels and blends become more cost-competitive. What I am most confident about is that the companies and utilities investing in flexible, adaptable infrastructure now will be better positioned than those waiting for certainty before acting. I have watched enough technology transitions to know that the window between when a new approach becomes viable and when the market broadly adopts it is where the important decisions get made. We at Mainspring believe that window is open right now. —Darrell Proctor is a senior editor for POWER.