Energy technology and manufacturing firm Form Energy has successfully closed a $750 million Series G funding round, marking a significant milestone in the global effort to stabilize renewable-heavy electric grids. The capital infusion is specifically earmarked to accelerate the manufacturing and commercial deployment of the company’s proprietary 100-hour iron-air battery systems. Based in Somerville, Massachusetts, Form Energy has emerged as a frontrunner in the long-duration energy storage (LDES) sector, a field increasingly viewed as the "missing link" in the transition from fossil fuels to a fully decarbonized power grid. This latest round brings the company’s total equity raised to over $2 billion, signaling robust investor confidence in the scalability of iron-based battery chemistry over traditional lithium-ion alternatives for grid-scale applications.
The Series G round was led by T. Rowe Price, which also spearheaded the company’s $405 million Series F round in late 2024. The participation list includes a diverse array of returning and new investors, reflecting the cross-sector appeal of Form Energy’s technology. Existing backers such as Prelude Ventures, Engine Ventures, TPG Rise Climate, and Breakthrough Energy Ventures—the investment firm founded by Bill Gates—reaffirmed their commitment. They were joined by a high-profile group of new institutional investors, including Sequoia Capital, Janus Henderson, Franklin Templeton, and PEAK6 Investments. This influx of capital arrives at a critical juncture as Form Energy transitions from a research and development focus to high-volume industrial production.
The Mechanics of Iron-Air Technology
At the heart of Form Energy’s value proposition is its iron-air battery technology, which operates on the fundamental principle of reversible rusting. While lithium-ion batteries are optimized for short-duration storage—typically four to eight hours—they become prohibitively expensive when scaled to meet multi-day demand. Form Energy’s solution utilizes iron, one of the most abundant and low-cost minerals on Earth, to store energy for up to 100 hours.
The discharge process involves the battery "breathing in" oxygen from the air, which reacts with the iron to create rust (iron oxide), releasing electrons in the process to power the grid. During the charging phase, an electrical current is applied to convert the rust back into metallic iron, releasing oxygen back into the atmosphere. Because the active components are iron, water, and air, the system avoids the supply chain volatility and environmental concerns associated with rare earth metals like cobalt and nickel. This long-duration capability is essential for managing "Dunkelflaute"—extended periods of low wind and solar output—and for ensuring grid resilience during extreme weather events, which are becoming more frequent and severe due to climate change.
Scaling Production at Form Factory 1
A primary objective of the $750 million funding is the continued expansion of "Form Factory 1," the company’s first high-volume manufacturing facility located in Weirton, West Virginia. The site selection carries significant symbolic and economic weight, as it occupies the grounds of the former Weirton Steel mill. By repurposing a site once central to the American coal and steel era for the production of green energy technology, Form Energy is positioning itself at the center of the "Just Transition" movement, which seeks to provide new industrial opportunities for communities affected by the decline of traditional manufacturing.
The Weirton facility is designed to reach a production capacity of 500 megawatts of annual battery output when fully operational. The Series G funds will facilitate the installation of advanced automated assembly lines and the hiring of hundreds of skilled workers. The company has noted that domestic manufacturing is not only a logistical advantage but also a strategic one, allowing it to benefit from tax credits and incentives provided under the U.S. Inflation Reduction Act (IRA), which prioritizes American-made clean energy components.
Commercial Traction and Strategic Partnerships
The funding announcement follows a period of rapid commercial acceleration for Form Energy. The company has secured landmark agreements with major utilities and technology firms, demonstrating that the market for 100-hour storage is maturing beyond the pilot phase.
In the utility sector, Xcel Energy has partnered with Form Energy to deploy a 10-megawatt/1,000-megawatt-hour iron-air battery system at the Sherburne County Generating Station in Becker, Minnesota. This project is a direct replacement for a retiring coal plant, showcasing how long-duration storage can provide the "firm" capacity needed to replace traditional baseload power. Similarly, Google has engaged with Form Energy to explore how multi-day storage can help the tech giant reach its goal of operating on 24/7 carbon-free energy across all its data centers and campuses by 2030.
Beyond the United States, the company is expanding its footprint through an agreement with FuturEnergy Ireland. This partnership aims to integrate iron-air batteries into the Irish grid to help manage the high variability of the country’s offshore and onshore wind resources. These contracts serve as a proof of concept for the "multi-day" category, proving that grid operators are willing to invest in technologies that go beyond the 4-hour window dominated by lithium-ion.
A Chronology of Growth
The trajectory of Form Energy reflects the broader evolution of the climate tech investment landscape over the last decade.
- 2017: Form Energy is founded by a team of industry veterans, including CEO Mateo Jaramillo, a former Tesla executive who helped start the Tesla Energy department, and MIT Professor Yet-Ming Chiang.
- 2018-2020: The company secures early-stage funding to prove the chemistry of iron-air batteries, focusing on safety and cost-efficiency.
- 2021: Form Energy announces its 100-hour battery technology to the public, sparking significant interest from utility providers.
- 2022: The company announces the selection of Weirton, West Virginia, for its first factory, supported by state and local incentives.
- 2024: A $405 million Series F round is completed, providing the capital necessary to break ground on Form Factory 1 and begin testing commercial-scale modules.
- 2026: The $750 million Series G round is finalized, bringing total investment to $2 billion and enabling the final push toward mass-market commercialization.
Market Context and Competitive Landscape
The global energy storage market is projected to grow exponentially as nations strive to meet net-zero targets. While lithium-ion remains the dominant technology for electric vehicles and short-term grid balancing, the "long-duration" segment is a distinct and rapidly growing niche. According to the Long Duration Energy Storage Council, the world will need between 1.5 and 2.5 terawatts of LDES capacity by 2040 to achieve full decarbonization.
Form Energy faces competition from other non-lithium technologies, including flow batteries (which use liquid electrolytes), thermal storage (which stores heat in bricks or sand), and compressed air energy storage. However, Form’s reliance on iron gives it a significant "cost-to-duration" advantage. Because the cost of iron is roughly 1/10th that of lithium, the marginal cost of adding more hours of storage to a Form Energy system is significantly lower than for a lithium-ion system.
Broader Implications for the Global Energy Transition
The success of Form Energy’s Series G round has implications that extend far beyond the company’s balance sheet. It serves as a validation of the "unbundled" grid model, where different technologies play specialized roles: solar and wind provide the bulk generation, lithium-ion handles short-term fluctuations, and iron-air provides the multi-day backup that keeps the lights on during "gray" weeks.
From a policy perspective, the massive private investment in Form Energy highlights the effectiveness of government frameworks like the Inflation Reduction Act in the U.S. and the Green Deal Industrial Plan in the EU. These policies have created a stable environment for long-term capital to flow into capital-intensive hardware projects.
Furthermore, the deployment of iron-air batteries could significantly reduce the need for new natural gas "peaker" plants. Currently, many utilities rely on gas plants to provide power when renewables are unavailable. By providing a cost-effective, carbon-free alternative for multi-day firming, Form Energy’s technology directly challenges the continued necessity of fossil fuel infrastructure in the power sector.
As Form Energy begins to roll out its systems at scale, the focus will shift to operational performance and durability. If the iron-air systems perform as expected in the field—withstanding decades of charge-discharge cycles without significant degradation—it could fundamentally change the economics of renewable energy, making a 100% clean grid not just a climate necessity, but an economic inevitability. The $750 million raised in this round provides the runway necessary to prove this thesis on the global stage.
