MN8 Puts $350 Million on a Reclaimed West Virginia Coal Mine, and Google Buys the Capacity

MN8 Energy, Google and Eos Energy Enterprises announced the Mammoth Solar project in Kanawha County, West Virginia on September 2, 2026. The site is a reclaimed coal mine. The build pairs 86 MW of solar with two different batteries. One is a 70 MW, 280 MWh lithium-ion system. The other is a 10 MW, 100 MWh zinc system from Eos, which gives it a 10-hour discharge. MN8 puts the capital cost at up to $350 million. MN8 will own and operate the plant. Google will buy the energy, the capacity and the clean energy attributes. The project connects to PJM and is meant to serve Google data centers in the region, including one planned for West Virginia. Solar comes online in 2028. The lithium battery follows in 2029. The zinc battery follows in 2030. MN8 expects construction to create about 200 jobs. It expects the plant to pay roughly $4 million in property tax to the county and local schools over the first 20 years of operation.

The announcement carries two first-of-a-kind claims. MN8 calls this the first commercial-scale long-duration storage deployment in West Virginia. Eos calls it Google’s first project using its American-made Z3 product. Eos builds a zinc hybrid cathode cell rather than a lithium cell. That chemistry trades energy density for duration and for a supply chain that does not run through lithium. The Eos unit holds 100 MWh behind 10 MW of power, so it discharges for 10 hours. The lithium system holds 280 MWh behind 70 MW, so it discharges for four. Running both lets one plant cover a short evening peak and a longer flat block from the same interconnection.

Why It Matters

The build order says what the partners treat as proven. Solar lands first in 2028. Lithium lands a year later. Zinc lands last in 2030, two years after the panels. Developers sequence a project that way when one part of the stack carries technology risk the rest does not. MN8 earns revenue from the solar and the lithium battery while the zinc system is still going in.

The site choice is the second signal. A reclaimed mine usually comes with graded land, road access and a transmission stub left from the mine load. Those three things shorten the two schedules that decide most projects, which are land assembly and interconnection. West Virginia holds a large stock of this land and almost no utility-scale solar sitting on it.

For Google the product is not clean electricity in the abstract. It is capacity shaped like a data center. A data center draws a flat load around the clock. Solar does not supply one. Putting 380 MWh across two batteries turns 86 MW of daytime output into a block a dispatcher can schedule against that load.

What Happens Next

Neither company published the contract term, the price, or the legal form of the deal. The wording says Google buys energy, capacity and attributes together, which is broader than a plain power purchase agreement and closer to a full offtake. The number to watch first is the PJM queue position and the date on the interconnection service agreement. Those decide whether 2028 is a schedule or an intention. The second is the Eos delivery. Google’s first Z3 project and West Virginia’s first commercial-scale long-duration system are the same 100 MWh of equipment, and it is the last piece to arrive.

Critical Perspective

Both first-of-a-kind claims in this announcement attach to the smallest and last piece of the project. The Eos zinc system is 100 MWh of the 380 MWh total, which is 26 percent of the storage. It is also the only component with a 2030 date on it. The solar starts in 2028 and the lithium battery in 2029. So the round-the-clock portfolio the partners describe does not exist for four years after the press release, and the part that makes it novel arrives last. Until 2030 this is an 86 MW solar plant with a conventional four-hour battery on it.

The local economics deserve the same arithmetic. About $4 million in property tax over the first 20 years works out to $200,000 a year. Set against up to $350 million of capital, that is 0.057 percent a year flowing to the county and its schools. The 200 construction jobs are real and they are temporary. MN8 has not put a number on the permanent operating jobs, which is the figure that decides what a reclaimed mine site is worth to Kanawha County after 2030.

One number is missing that would let a reader check the rest. Nobody has published the size of the Google load this project is matched to. Storage sized at 380 MWh means nothing on its own. It means something only against a stated megawatt draw and a stated number of hours. The partners describe capacity shaped to a data center profile without saying whose profile, or how much of it 86 MW and 380 MWh actually covers.

Sources

• GlobeNewswire: MN8 Energy, Google, and Eos Energy Enterprises Bring Advanced Clean Energy Solutions to West Virginia
• Energy-Storage.News: Google partners with MN8 Energy and Eos on West Virginia solar-plus-LDES project
• pv magazine USA: Google backs 100 MWh zinc, 280 MWh lithium storage project in West Virginia
• Data Center Dynamics: Google partners with MN8, Eos on West Virginia solar + storage project

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