Nobody Will Say How Big xAI’s Memphis Battery Is: 2.8 GWh Counted, 3.3 GWh Claimed, 2,000 MW Described
- Data Centers Grid Connection & Reliability News
Marin Holt
- 0
- 7 minutes read
- Containers counted in satellite imagery: 720 Tesla Megapacks
- Canary Media estimate: 2.8 GWh
- Figure given to the TVA board: 3.3 GWh
- Figure given by MLGW's CEO: 2,000 MW
- Current largest US battery: 1,066 MW
xAI has built a battery at its Colossus 2 data center in Memphis, Tennessee, and three separate accounts size it three different ways. None of the three agree. Neither the company nor either of its two utilities will confirm a number.
Canary Media counted 720 Tesla Megapack containers on the site in satellite imagery dated July 11. The outlet put that at 2.8 GWh, and at between 720 MW and 1,400 MW of discharge depending on which Megapack model is installed. Tesla rates each Megapack at more than 3.9 MWh.
On August 20, Riley Trettel, an energy and data center developer at the company, told the Tennessee Valley Authority board the battery holds 3.3 GWh. Trettel said that was enough to power all of Memphis for two hours. He also said it was not yet connected to the TVA grid. The board approved a direct hookup later the same day. TVA generates power for 10 million people across the Southeast.
On September 2, Memphis Light, Gas and Water CEO Doug McGowan gave a third figure at a solar and storage conference in Chattanooga. “I think it’s 2,000 MW of batteries behind the meter that they have to help as a backup when they have to curtail,” McGowan said. MLGW supplies the site. Its communications team declined to clarify the number and referred questions to TVA. TVA declined to comment and referred questions back to the company. The company has not answered requests for comment.
Any of the three figures would make this the largest battery in the United States. The present record holder is the Edwards & Sanborn solar plant in Kern County, California, at more than 1,066 MW and 3,287 MWh.
No announced utility contract sits behind the buildout. Regional storage developers first heard about the battery at the August TVA board meeting. Tesla disclosed in a January filing with the Securities and Exchange Commission that xAI bought $430 million of Megapacks last year. SpaceX acquired xAI in February. The combined company bought another $405 million of Megapacks in the first half of this year.
Colossus 2 occupies about 1 million square feet at 5400 Tulane Road in the Whitehaven section of Memphis. The company bought the property for a reported $80 million through an affiliate. The site sits close to TVA’s 780 MW Southaven combined cycle plant. Company officials have said the data center could host up to 350,000 GPUs.
Why It Matters
A battery this large normally arrives with a signed utility contract, an interconnection study and a permit record that states its rating. This one arrived with none of that. The two insider figures also measure different things. Trettel gave an energy rating and tied it to two hours of Memphis demand. McGowan gave a power rating and tied it to backup for the moments the site has to curtail. One number tells you how long the campus holds out. The other tells you how hard it hits the grid when it stops drawing. Southeast planners have filed figures for neither.
Critical Perspective
The three figures are not equally load-bearing. Canary Media’s 2.8 GWh rests on counting containers in one satellite image from July 11. That fixes a floor and little else, because a photograph does not show a model number, and Tesla started building the larger Megapack 3 in early August, after that image was taken. Trettel gave his 3.3 GWh to a board he was asking for an interconnection. McGowan’s bigger number arrived with its own hedge, “I think,” from a utility that then declined to clarify it.
What none of the three settles is who gets to call on the battery. A pack sized as behind-the-meter backup for curtailment answers to the data center, not to a dispatcher, and TVA declined to comment on it at all. The board approved the hookup the same day it heard the 3.3 GWh figure. Until an interconnection agreement or a permit states a rating, the largest battery in the country is a number three parties have described three ways. The more useful question is not how big it is, but whose instruction it follows.
