Google turns to Eos Energy for long-duration storage as West Virginia data-center power demand grows

Eos Energy Enterprises Inc. shares surged on September 2 after the battery manufacturer joined MN8 Energy and Google in a clean-energy project designed to support rising electricity demand from data centers across the PJM Interconnection region. The Mammoth Solar development in West Virginia will combine 86 megawatts of utility-scale solar generation, 70 megawatts and 280 megawatt-hours of lithium-ion storage, and a 10-megawatt, 100-megawatt-hour Eos Z3 zinc-based long-duration energy storage system. Google will purchase the project’s electricity, capacity and clean-energy attributes, while MN8 Energy will own and operate the development. The Eos system is designed to provide 10 hours of storage and represents Google’s first deployment of the company’s United States-manufactured Z3 technology. Eos Energy Enterprises shares climbed by double digits following the announcement, reflecting investor enthusiasm around the commercial validation provided by one of the world’s largest data-center operators.

The individual Eos deployment is relatively modest compared with the company’s broader commercial pipeline, but its strategic importance is much larger than the 100-megawatt-hour capacity alone suggests. Mammoth Solar is the first project being developed under an existing master supply agreement between MN8 Energy and Eos Energy Enterprises that covers up to 750 megawatt-hours, giving investors an early indication that the framework is moving from contracted capacity toward identifiable projects.

Google agreement gives Eos Energy a high-profile test of zinc-based long-duration storage for data centers

Mammoth Solar will be developed on a reclaimed coal mine in Kanawha County, West Virginia, where MN8 Energy plans to combine solar generation with two different battery technologies. The lithium-ion system will provide shorter-duration storage, while Eos Energy Enterprises’ Z3 system is designed to discharge for 10 hours, extending the availability of renewable electricity beyond periods of direct solar production.

The project is scheduled to come online in stages rather than simultaneously. Solar generation is expected to begin commercial operations in 2028, followed by the lithium-ion storage component in 2029 and Eos Energy Enterprises’ long-duration storage system in 2030, meaning the market reaction is based primarily on future commercial validation rather than near-term project revenue.

Google’s involvement strengthens the project’s relevance to the rapidly expanding data-center power market. Google indicated that the collaboration is designed both to support electricity requirements associated with its regional data-center operations, including a planned West Virginia project, and to accelerate commercialization of long-duration storage technologies capable of providing more dependable clean electricity across the grid.

For Eos Energy Enterprises, that external validation matters because data centers have become an increasingly important portion of its sales pipeline. The company said during its second-quarter earnings discussion that roughly 32% of its approximately $24.6 billion commercial opportunity pipeline was related to data centers, a significant shift for a market that represented only a minimal portion of its opportunities several years earlier.

Management has positioned zinc-based long-duration storage as particularly suitable for applications requiring electricity across eight or more hours. That places Eos Energy Enterprises in a different segment from conventional lithium-ion batteries commonly deployed for shorter-duration grid balancing, although the West Virginia project demonstrates that the technologies can also operate together rather than functioning strictly as competitors.

MN8 Energy agreement could make the 100 MWh Google deployment the first step in a much larger storage relationship

The Mammoth Solar project represents the first deployment under a previously announced master supply agreement covering up to 750 megawatt-hours of Eos Energy Enterprises storage capacity for MN8 Energy. The agreement marked a transition from an earlier commercial relationship into contracted storage capacity and was designed partly around large-load customers such as hyperscale data centers.

The initial Google-linked deployment accounts for 100 megawatt-hours of that potential capacity, leaving substantial room for additional projects if development and operating performance meet expectations. Earlier company commentary indicated that the first several 10-hour projects under the MN8 Energy relationship were expected to total around 200 megawatt-hours, making Mammoth Solar an important commercial reference point for the broader arrangement.

MN8 Energy itself has more than four gigawatts of operating and under-construction assets across 29 states and serves more than 200 customers, including artificial intelligence companies, hyperscale technology groups, Fortune 500 corporations and government agencies. The company’s customer relationships could therefore create additional opportunities for Eos Energy Enterprises if long-duration storage becomes a larger component of behind-the-meter and grid-connected power strategies.

The West Virginia investment also carries an economic-development dimension. MN8 Energy estimates Mammoth Solar could represent as much as $350 million of capital investment, generate approximately $4 million in property tax revenue for Kanawha County and local schools during its first 20 years, and support roughly 200 construction jobs.

For Google, the broader objective is not simply to purchase renewable electricity when the sun is producing power. Pairing solar with both short-duration and long-duration batteries creates a more dispatchable resource that can better match the relatively continuous electricity requirements of data centers, potentially increasing the usefulness of new renewable generation without requiring equivalent fossil-fuel backup capacity during every hour.

Record Eos Energy backlog strengthens the growth story but manufacturing losses remain the major investor risk

The Google announcement arrives after Eos Energy Enterprises reported substantial commercial growth during the second quarter. Revenue increased 351% year over year to $68.8 million as battery-system deliveries accelerated, while backlog reached a record $807 million, representing approximately 3.4 gigawatt-hours of storage capacity and increasing 25% sequentially.

The company’s wider commercial pipeline reached approximately $24.6 billion and nearly 112 gigawatt-hours at June 30. Roughly 51% of that pipeline involved projects requiring at least eight hours of storage, aligning directly with the long-duration market where Eos Energy Enterprises believes its zinc chemistry has stronger economic differentiation.

Rapid revenue growth has not yet translated into positive manufacturing economics. Eos Energy Enterprises reported a second-quarter gross loss of $48.8 million and a negative gross margin of 71%, although that represented a substantial improvement from the prior year as higher production volumes reduced unit costs. Adjusted EBITDA loss widened to $71.4 million, underscoring the continuing need to achieve greater manufacturing scale and efficiency.

Management tightened full-year 2026 revenue guidance to between $300 million and $350 million from the previous range of $300 million to $400 million. The company also began commercial production on a second manufacturing line and has been consolidating battery production at its Thorn Hill facility near Pittsburgh in an effort to lower conversion costs and improve margins as shipment volumes increase.

Liquidity gives the company time to pursue that strategy, with total cash including restricted cash reaching approximately $364.1 million at June 30. However, the central financial challenge remains unchanged: Eos Energy Enterprises must demonstrate that rising sales and backlog can eventually produce positive gross margins and sustainable cash generation rather than simply increasing manufacturing losses alongside revenue.

Eos Energy stock rally reflects Google validation but the shares remain deeply volatile

Investor sentiment turned sharply positive following the September 2 announcement. Eos Energy Enterprises shares rose around 12% in early trading, while premarket gains had reached approximately 15% at one stage as investors responded to Google’s involvement and the first deployment under the MN8 Energy master supply agreement.

The rally needs to be placed within a much more volatile longer-term picture. Eos Energy Enterprises closed September 1 at approximately $3.04 after trading above $8 during June, meaning the shares had lost more than 60% from their recent peak before the Google announcement. The stock had also fallen close to a 52-week low around $3, making the September 2 rebound significant without erasing the substantial decline experienced over the preceding months.

That volatility reflects competing investment narratives. The bullish case centers on record backlog, growing demand for long-duration storage, United States manufacturing, data-center exposure and high-profile partnerships involving companies such as Google, MN8 Energy and Talen Energy. Eos Energy Enterprises has also expanded into defense-related applications and reported a strategic relationship connected with the Golden Dome for America program, broadening potential demand beyond commercial grid projects.

The bearish case remains rooted in profitability and execution. Negative gross margins mean Eos Energy Enterprises is still spending significantly more to manufacture and deliver systems than it generates in gross profit, while scaling a new battery technology introduces production, reliability, financing and project-delivery risks that could become more visible as contract sizes increase.

Mammoth Solar will not resolve those concerns immediately because Eos Energy Enterprises’ portion is not expected to begin operating until 2030 and the financial value of the company’s supply contract for the project has not been disclosed. Its importance instead comes from demonstrating that a major hyperscale technology company is willing to incorporate Eos zinc batteries into a commercial data-center power strategy alongside established lithium-ion technology.

If the project performs as expected and additional MN8 Energy deployments follow, that validation could improve the probability that Eos Energy Enterprises converts more of its $24.6 billion opportunity pipeline into firm orders. The investment case will still depend on whether the company can manufacture those systems profitably, making operational efficiency and gross-margin improvement as important as the next major customer announcement.

Key takeaways from Eos Energy’s Google-backed West Virginia battery project and stock rally

• Eos Energy Enterprises is supplying a 10 MW/100 MWh zinc-based long-duration battery system for an MN8 Energy project supporting Google’s regional data-center electricity needs.
• Mammoth Solar will combine 86 MW of solar, 70 MW/280 MWh of lithium-ion storage and Eos Energy Enterprises’ 10-hour Z3 long-duration storage technology.
• Google will purchase the project’s electricity, capacity and clean-energy attributes, giving Eos Energy Enterprises a high-profile commercial validation from a major hyperscale data-center operator.
• The West Virginia deployment is the first project under the existing MN8 Energy and Eos Energy Enterprises master supply agreement covering up to 750 MWh of storage capacity.
• MN8 Energy estimates the overall project could represent as much as $350 million of capital investment and create roughly 200 construction jobs in West Virginia.
• Eos Energy Enterprises entered the announcement with a record $807 million backlog representing approximately 3.4 GWh of contracted storage capacity.
• The company’s wider commercial pipeline stands near $24.6 billion, with data-center opportunities representing an increasingly important component of potential future demand.
• Eos Energy Enterprises still faces significant execution risk after reporting a $48.8 million second-quarter gross loss and a negative 71% gross margin despite rapidly increasing revenue.
• Shares surged by double digits following the Google announcement, reversing part of a steep decline that had pushed the stock close to its 52-week low.
• Long-term shareholder value will depend on whether high-profile deployments such as Mammoth Solar lead to additional orders while manufacturing scale drives margins toward sustainable profitability.