Google to buy from 86 MW solar and zinc storage project in West Virginia

MN8 Energy will build 86 MW of solar with 70 MW/280 MWh of lithium-ion batteries and 10 MW/100 MWh of Eos Energy Enterprises' zinc-based storage at its Mammoth Solar site in Kanawha County, West Virginia, and Google will buy the project's energy, capacity, and clean energy attributes, the three companies announced on September 2, 2026. MN8 expects the solar to reach commercial operation in 2028, the lithium-ion storage in 2029, and the zinc system in 2030. The release puts the capital investment at up to $350 million, on MN8's estimates, and calls the project the first commercial-scale long-duration energy storage deployment in West Virginia.

The zinc unit is a 10-hour battery and the lithium-ion unit a four-hour one (the arithmetic is in kW vs kWh). Per the release, the longer unit extends solar output "beyond the shorter-duration energy storage resources," and the integrated portfolio "adds new clean, dispatchable capacity to the grid serving Google's data centers in the region, including a planned project in West Virginia," with the design described as capacity "matched to data center load profiles." The release describes the site as "a reclaimed coal mine"; the Public Service Commission of West Virginia's 2025 management summary report says the project boundary in the siting application covered approximately 1,148 acres of reclaimed surface mine land, with the facilities themselves on about 446 acres.

The release calls the project "the first project under the previously announced MN8-Eos Master Supply Agreement," a supply agreement Eos announced on October 21, 2025 for as much as 750 MWh of its Z3 systems to MN8. That earlier release said the first projects MN8 would consider for Z3 "would incorporate 200 MWh of storage systems with 10-hour energy discharge duration," so Mammoth takes half of the opening tranche. The September 2 release also calls this Google's first project using Eos' Z3 technology. Google's own post the same day goes further, describing "a first of its kind deployment of these zinc-hybrid batteries, manufactured by Eos in Pennsylvania," a claim the joint release does not make. The Eos quote in that joint release is attributed to Nathan Kroeker as chief commercial officer; Eos announced on August 25, 2026 that Michelle Buczkowski had succeeded him in that role effective August 24, with Kroeker leaving the company on October 20, 2026.

What the docket says

The siting case predates the Google announcement. According to the PSC's management summary report, Mammoth Solar, LLC applied on June 30, 2025 for a siting certificate to build a 90 MW solar facility and up to 90 MW of battery storage as an exempt wholesale generator, at an estimated cost of $189.5 million, and supplemented the application on August 14, 2025 to say the storage would be built and owned by an affiliate, Mammoth BESS, LLC. The commission's final order of November 24, 2025 in case 25-0594-E-SCS-PW granted the two companies a certificate for a 90 MW facility of approximately 193,000 modules that will interconnect with an existing Appalachian Power 138 kV line, the Kanawha River to Carbondale circuit, which crosses the site. Among the order's conditions: begin continuous construction within five years of the order and finish within ten, and meet the state's decommissioning bonding requirements.

Some numbers moved between the docket and the release. The certified 90 MW is 86 MW in the announcement. The $189.5 million estimate in the application, which already included up to 90 MW of storage, is "up to $350 million" in the release, whose two storage units add up to 380 MWh. The release expects construction to create approximately 200 jobs; in the docket, MN8 witness David G. Loomis testified the project "will support 159 new local jobs during construction for Kanawha County and 238 new local jobs during construction for the State of West Virginia." The release's approximately $4 million in property tax revenue for the county and local schools over the first 20 years of operations sits beside the project's community website, which gives "up to an estimated $3.5 Million in new county revenue for the first 20-years of operation" and targets construction start in the first quarter of 2027. An MN8 spokesperson told ESS News, in a report pv magazine USA republished on September 3, that the project is the same Mammoth Solar development previously permitted in Kanawha County; in the same spokesperson account, Google's participation as offtake partner came after the project was already in development, "but the tech giant helped shape the technologies that were ultimately selected."

The "planned project in West Virginia" lines up with the data center campus Google is developing in Putnam County. Governor Patrick Morrisey's office announced on March 27, 2026 that Google had purchased land there and received approval for a High Impact Data Center Project; Google's Clay Allsop said in that release the company was "early in the process, and substantial work remains." The MN8 release links Google's "commitment to bring new capacity to the grids where it operates" to a March 4, 2026 post in which Google said it was signing the White House Ratepayer Protection Pledge and committed "to bringing net-new energy to the grid," naming long-duration storage among the technologies it would invest in.

The grid the plant joins is short of capacity. PJM's 2028/2029 Base Residual Auction, announced July 14, 2026, cleared at the FERC-approved price cap of $325 per MW-day across the entire footprint, and even with 10,864 MW from regions that self-supply under the Fixed Resource Requirement, committed capacity fell 6,831 MW short of PJM's reliability requirement. That shortage is the backdrop for Google's other 2026 capacity purchases: Voltus's Google-funded virtual power plant in PJM, under a three-year agreement announced June 2, 2026 to aggregate up to 100 MW of distributed resources a year, whose Bring Your Own Capacity programs Sunrun agreed on August 17, 2026 to supply from its residential solar-plus-storage fleet, and, in the West, a 396 MW geothermal contract with Fervo signed August 26, 2026 for a possible Utah data center. Mammoth adds a 10-hour battery to that list.

Outlook

The dates to watch are the ones the documents set. MN8's community site targets construction start in the first quarter of 2027, and the siting certificate requires continuous construction to begin within five years of November 24, 2025, so the 2028 solar date has room on the regulatory side. The zinc unit's 2030 date depends on Eos as much as on MN8: Eos said on August 27, 2026 it is consolidating battery manufacturing at its Thorn Hill plant in Warrendale, Pennsylvania, with nameplate capacity expected to be approximately 4 GWh once both lines are operating, which would make Mammoth's 100 MWh a small draw on the factory if the consolidation lands as described. On the buyer's side, the governor's release quotes Google calling the Putnam County campus early in the process. The joint release frames the offtake as energy, capacity, and attributes delivered to the PJM grid rather than a direct supply to the data center, which suggests the plant would still have a market if the campus slips; that reading is ours, not any party's.