On July 2 the Shelby County Health Department granted xAI an air permit to run 15 natural gas turbines at its Colossus data center in South Memphis. The permit ends a year in which the company powered one of the world's largest AI training clusters partly with mobile turbines that it said did not need permits, and it opens a fight over whether the county should have required more. The episode is the sharpest example yet of a pattern the power sector is now confronting: AI developers can build compute faster than utilities can deliver electricity, and they fill the gap with on-site generation.
What the permit allows
According to Ars Technica, the permit covers 15 turbines and expires on January 2, 2027. It requires xAI to install and operate best available control technology by September 1 so that emissions stay within set limits. It also limits the 15 turbines to a maximum of 22 startup events and 22 shutdown events per year, with a combined duration of 110 hours a year, and no single event longer than one hour. Local station Action News 5 reported that the permit caps 12-month rolling emission rates, which xAI must record monthly, and that the 15 turbines were approved as permanent installations.
The health department told the Southern Environmental Law Center that much of its concern related to temporary turbine engines, which were scheduled to be removed by the end of July, Action News 5 reported.
The objection
SELC, which represents the NAACP and local groups, says xAI installed 35 gas turbines at the site without permits after it began operating in June 2024. It says a satellite image taken on July 1 showed at least 24 turbines still on site, more than the 15 covered by the new permit. The Sierra Club's Tennessee chapter said the department should have imposed pollution control requirements on all the turbines and pursued enforcement against xAI for running them without best available controls or a permit for more than a year. SELC said it was evaluating its options, and Action News 5 reported that SELC and the NAACP intend to sue.
Fox 13 reported that the facility had been using temporary turbines that were allowed to operate for only a year, and that with the year nearly up, the county cleared the switch to permanent units. In other words, the permit formalizes a smaller, controlled fleet rather than ending on-site generation at Colossus.
The grid side
The turbines exist because the grid could not supply the load quickly enough. Memphis Light, Gas and Water set out the electricity picture in a public update on May 5. xAI occupies a former Electrolux factory on Paul Lowery Road in Frank C. Pidgeon Industrial Park, which also hosts TVA's Allen combined cycle plant, Nucor Steel and the city's Maxson wastewater plant. The building itself was put up with a $97 million state grant in 2010, and MLGW notes it came with a 15-year local property tax abatement of 75%. MLGW says xAI requested two successive increments of 150 MW, for 300 MW in total.
The first increment is done. MLGW and TVA completed system impact studies, transmission upgrades were finished at xAI's expense, and xAI paid for a new substation. The TVA board approved 150 MW, which now reaches the site through two substations: 8 MW from an existing MLGW substation and 142 MW from the new one. xAI pays the prevailing industrial rate.
The second 150 MW is in progress. MLGW says the studies are complete, upgrades have been identified, and a second substation is under construction at xAI's expense. TVA's board has not yet decided. If it approves, MLGW projects that the site will have 300 MW from the grid by no later than December 2025. MLGW also says TVA, xAI and MLGW have signed an agreement requiring xAI to curtail its grid consumption when demand is high.
MLGW draws a clear line around its role. It says it has no authority over xAI's use of turbines or any other behind-the-meter generation on private property, and that local, state and federal rules govern them.
Bigger plans
The Paul Lowery site is not the end of it. MLGW says xAI has secured a second large facility on Tulane Road near the Tennessee-Mississippi state line, close to TVA's Southaven combined cycle plant and a large TVA and MLGW substation. MLGW received an initial request for 260 MW of grid power there, which was not studied, and says options from 260 MW to 1.1 GW have since been discussed. It is awaiting a final request before starting a system impact study. xAI has also asked MLGW to study whether it can supply more natural gas to the Tulane site.
Water is part of the picture. MLGW says xAI offered to build, at its own expense, a plant that would treat discharged water from the city's Maxson wastewater plant and produce 13 million gallons a day of recycled water for xAI, TVA, Nucor Steel and others, reducing pressure on the aquifer.
Why it matters beyond Memphis
The arithmetic is simple. A supercomputer can be assembled in months. A substation and transmission upgrade take longer, even when the customer pays. The 150 MW that the grid supplies now is roughly what the first phase of a large AI cluster needs, and the developer's ambitions are larger. On-site turbines are the obvious bridge, and gas is available through existing mains. MLGW says xAI paid for an 8-inch tap on the 16-inch main in Paul Lowery Road.
The cost of that bridge falls on the neighborhood. South Memphis already hosts heavy industry and a gas-fired power plant, and residents' complaints are about air quality, not electricity bills. The new permit brings 15 turbines under emissions controls and reporting. It leaves open what happens to any units beyond that number and how regulators should treat the next developer that wants to start running before the grid is ready.
Other regions will face the same choice. As grid operators struggle with interconnection queues measured in years, the temptation to power AI campuses first and permit them later will grow. Memphis shows how quickly that becomes a local environmental dispute.