XAI builds massive battery at Memphis data
Elon Musk's xAI has installed a massive battery system at its Memphis data center, potentially the largest in the U.S., with capacity estimates ranging
Elon Musk's xAI has built what may be the largest battery in the United States at its Memphis data center hub. The exact size of the installation is unclear, but estimates from satellite imagery and utility officials suggest a capacity between 2.8 and 3.3 gigawatt-hours.
On August 20, xAI energy and data center developer Riley Trettel told the Tennessee Valley Authority board the facility has 3.3 GWh of storage, enough to power all of Memphis for two hours. He said the battery was not yet grid-connected but could be by the end of the year if approved. The TVA board approved a direct grid hookup for xAI that same day.
Memphis Light, Gas and Water CEO Doug McGowan corroborated the scale of the project at a September industry conference. McGowan, whose utility supplies the facility, described it as having "the world's largest grid-connected battery system." He estimated it at 2,000 megawatts of behind-the-meter batteries for backup during curtailment.
Conflicting capacity estimates
Canary Media counted 720 Tesla Megapack battery containers visible in July 11 satellite imagery of the Colossus 2 data center site. That visible count would equate to approximately 2.8 gigawatt-hours of storage and between 720 and 1,400 megawatts of power output, depending on the specific Megapack model used.
If the installation has grown since July to the capacities cited by officials, it would surpass the current largest known U.S. Grid battery. That title is held by the Edwards & Sanborn solar plant in Kern County, California, with more than 1,066 MW and 3,287 MWh.
| Facility | Location | Capacity (Power) | Capacity (Energy) |
|---|---|---|---|
| Edwards & Sanborn solar plant | Kern County, California | >1,066 MW | 3,287 MWh |
| xAI Colossus 2 data center (estimated) | Memphis, Tennessee | 720-2,000 MW | 2.8-3.3 GWh |
Both TVA and MLGW declined to clarify the official battery size, referring inquiries to xAI. XAI has not responded to requests for comment.
Procurement and rapid deployment
XAI purchased $430 million worth of Megapacks last year, according to a Tesla filing with the Securities and Exchange Commission. After xAI was acquired by SpaceX in February, the combined company bought another $405 million worth of Megapacks in the first half of this year.
The rapid deployment is unusual for a grid-scale project. Such installations normally take years to develop, requiring community outreach, permits, and utility contracts to guarantee revenue. Regional storage industry leaders first heard about the xAI battery at the August TVA board meeting.
Tesla began production of a new, more powerful Megapack 3 model in early August. This redesign aims to speed up deployment, raising the possibility that significantly more battery capacity could have been installed at the site over the past month.
Grid integration and demand management
The massive battery is part of a "power interruption" program run by MLGW. Doug McGowan explained the setup at the conference. "They actually have behind-the-meter..." he said.
This ability to disconnect from the grid during peak demand was a precondition for hooking up service to the data center. The approach allows local power companies in TVA territory to implement solutions for fast-moving AI demand without waiting for yearslong regulatory approvals.
Other developers are pursuing similar strategies. Aligned Data Centers will come online early in Oregon by paying the utility to build a battery for peak capacity. Google signed up a portfolio of solar, wind, and batteries to run a Minnesota data center.
Context and potential grid benefits
XAI has previously used temporary gas generators to run its Memphis computing infrastructure before sufficient grid supply was available. The company has been operating 69 mobile gas generators without air permits at the Colossus 2 site as of July. The Southern Environmental Law Center has sued to stop this unpermitted air pollution on behalf of the nearby communities.
It remains unclear whether the new battery will lead xAI to reduce its use of these generators. If the batteries lack sufficient grid power, they could charge from the generators in an islanded microgrid setup, incurring further emissions.
TVA has identified battery storage as a growth opportunity in its long-range energy plan. The federal utility seeks more firm, dispatchable power to meet peak demand from a growing population, manufacturing base, and AI industries. Batteries could shift energy from nighttime surplus periods to high-demand afternoon and evening hours, while also storing the region's growing solar generation.
"We're just beginning to tap the potential of battery storage in the Tennessee Valley," said Gil Hough, executive director of the Tennessee Solar Energy Industries Association. He suggested the project could be a catalyst for utilities and developers to think bigger about how storage can meet rapidly growing electricity demand.
TVA operates a large fleet of nuclear and coal plants that cannot nimbly ramp up and down. These plants create periods of electrical surplus at night when demand is low.
