SpaceXAI's Memphis battery draws conflicting capacity claims as TVA weighs grid approval
Two executives gave figures that cannot be reconciled, leaving the TVA board to rule on a connection without verified public data.
SpaceXAI energy and data centre developer Riley Trettel told the Tennessee Valley Authority board on September 10 (2026-09-10) that the company's Memphis computing hub holds 3.3 GWh of storage, "enough to power all of Memphis for two hours," and that grid connection was pending board approval later this year.4
The number TVA's own representative offered was different. On September 11 (2026-09-11), TVA's McGowan described the same site as hosting "the world's largest grid-connected battery system" with "I think it's 2,000 MW of batteries behind the meter."4 Canary Media counted 720 Tesla Megapack units at the facility, which would equate to 2.8 GWh and between 720 MW and 1,400 MW of capacity depending on the model installed.4 Three sets of figures from three sources. None reconcile.
For context, the largest known operating grid battery in the US sits at the Edwards and Sanborn solar plant in Kern County, California, with more than 1,066 MW and 3,287 MWh.4 Memphis may already exceed it. Whether it does depends entirely on which estimate is accurate, and none of the parties has published documentation to settle the question.
TVA serves 10 million people across the Tennessee Valley.4 Behind-the-meter storage at this scale shifts when a site draws power but does not reduce total consumption. If the Memphis batteries charge overnight and discharge during afternoon peaks, the net load profile imposed on TVA's system depends on the charge-discharge schedule. Neither Trettel nor McGowan addressed that schedule in public remarks.
The capital deployed is not in dispute. XAI bought $430 million worth of Megapacks last year, a figure Tesla acknowledged in a January filing with the Securities and Exchange Commission.4 SpaceX acquired xAI in February, and the combined company purchased another $405 million of Megapacks in the first half of this year.4 Combined, roughly $835 million of Tesla storage hardware has moved to one site in under eighteen months — enough to make this material to Tesla's energy segment regardless of how the gigawatt-hour figure resolves.
The gap between the two executive statements is not small. Trettel's 3.3 GWh implies roughly 2.9 hours of discharge at McGowan's 2,000 MW figure, or close to 1.9 hours at the top of the Canary Media range. One of those numbers is wrong, or the installation changed between the two briefings, or both speakers were estimating. The TVA board has been asked to approve a grid connection without a public interconnection agreement, charge schedule, or cell count.4
Fluence Energy's mid-May run illustrates where investor attention has moved. Shares gained 98% in one week in May 2026 as capital rotated into companies supplying power for AI buildouts.2 Fluence reported a record backlog, signed master supply agreements with two major hyperscalers, and reaffirmed 2026 revenue guidance of approximately $3.2 billion to $3.6 billion, with 85% of the midpoint already contracted.1 A secondary offering of 20 million Class A shares diluted that momentum, and the company remains loss-making.1 The tailwind is genuine; the profit is not yet visible.
The URA uranium ETF closed at $43.53 on September 12 (2026-09-12), down 3.25% in the most recent session.4 Nuclear is frequently cited as the long-horizon answer to data centre power demand. China is building 45% of the roughly 60 reactors under construction globally and aims to raise nuclear's share of its electricity from around 5% to 18% by 2060.3 Memphis is not that story. It is a storage and interconnection story unfolding now, built on hardware that was purchased and installed faster than any reactor programme could move.
The TVA board decision on the grid connection is the next concrete data point. Until the board rules and publishes terms, the capacity of what may be the largest battery installation in the country remains a matter of competing verbal estimates from two executives who gave different numbers on consecutive days.4