Is xAI Sustainable? What SpaceX’s Filings Reveal About Grok’s Footprint

Most AI labs make you guess what powers their models. xAI, now SpaceXAI, tells you in a securities filing. Its data centres were brought online “almost entirely through on-site power generation”, and the newest of them can run entirely on its own gas power plant. Its environmental record is also being argued in a federal court in Mississippi.

So is xAI sustainable? xAI publishes no sustainability report, no emissions figures and no climate target. The closest primary disclosure is what its parent company, SpaceX, has filed with the US Securities and Exchange Commission since xAI was folded into it in February 2026. Those filings describe AI infrastructure that runs mostly on natural gas. None of them puts a number on the emissions. On the evidence available, Grok runs on infrastructure its own owner describes as mostly gas-powered, and nobody outside the company can measure what that costs the climate.

This audit reads SpaceX’s final prospectus (12 June 2026) and its quarterly report for July to September 2026, walks through the two Colossus data centres, and applies the same questions I asked of Anthropic in Is Claude Sustainable?

This piece is one of four. The synthesis, with a side-by-side comparison of Anthropic, OpenAI, xAI and Google, is Is Generative AI Sustainable?

Does xAI Publish a Sustainability Report?

No. xAI never published one as an independent company, and SpaceX has not published one since the merger. The prospectus and the quarterly reports that followed contain no greenhouse gas figures. The word “emissions” appears only in connection with rocket launches and in a list of environmental laws. There is no figure for the electricity Grok consumes, the gas burned to produce it, or the water used to cool the servers.

What the filings do give is unusually direct qualitative disclosure about power. It is more direct than anything Anthropic’s S-1 says about its own sites. That candour is useful to a reader, and it also sets a floor. A company that knows its power comes from its own turbines has the meter readings to report Scope 1 emissions whenever it chooses.

Environmental disclosure	What xAI and SpaceX publish (October 2026)
Sustainability or ESG report	None
Scope 1, 2 and 3 emissions	None
Climate or net-zero target	None
Power sources for AI data centres	Qualitative. “Significantly” natural gas and gas turbines (prospectus, p. 37)
AI compute capacity	About 1.0 GW across Colossus and Colossus II (p. 95). 1.7 GW nameplate at 30 September 2026 (Q3 10-Q)
Water use	None. Water scarcity named as a risk (p. 37)
Per-query energy for Grok	None. Efficiency claims are given in tokens and price
Environmental litigation	Disclosed, without an estimate of exposure

What SpaceX’s Filings Say About Grok’s Power

The prospectus describes xAI’s infrastructure as one “coherent gigawatt-scale AI training cluster” around Memphis, Tennessee, extending into northern Mississippi. The flagship Colossus campus sits on Paul R. Lowry Road in Memphis. Colossus II covers two further sites, on Tulane Road in Memphis and on Stateline Road in Southaven, Mississippi (pp. iv and 210). Together, Colossus and Colossus II “collectively provide approximately 1.0 gigawatt of compute power” (p. 95).

The power story is told with some pride. Both data centres “were brought online almost entirely through on-site power generation capabilities that we designed, built, and deployed ourselves” (p. 95). Going forward, Colossus II “is expected to be primarily powered by a dedicated natural gas power plant, supplemented over time by additional grid capacity”. Page 195 goes further and says Colossus II can run entirely on that “self-built behind-the-meter gigawatt-scale natural gas power plant”, and that its next expansion is designed to train Grok-5. At the original Colossus site, SpaceX buys grid power when it is available and falls back on its own generation and Megapack batteries when the grid is curtailed.

Two more figures show the direction of travel. On 30 April 2026 SpaceX agreed to buy “certain mobile gas turbines and related packages for approximately $2,000 million” to power its data centres (p. F-62). And its quarterly report for the third quarter of 2026 puts installed AI compute at 1.7 GW of nameplate power on 30 September, up from 0.6 GW a year earlier. That metric counts only the GPUs. It excludes cooling, power distribution losses and the rest of the facility, so the electricity the sites draw is higher.

The same risk factor that names gas also names water. Water scarcity, drought, competition for local water or restrictions on its use “could limit our ability to obtain sufficient water for cooling” (p. 37). As with energy, there is no figure for how much water the sites use.

Colossus, Memphis

The first Colossus came online in mid-2024 in a former factory in Memphis, with its first cluster running 122 days after work began, by SpaceX’s account (p. 95). Its early power supply is the origin of the local controversy. According to the Southern Environmental Law Center, xAI ran as many as 35 unpermitted gas turbines at the site before obtaining permits for the remaining 15.

Water is the second front in Memphis. The city draws its drinking water from the Memphis Sand Aquifer, and xAI’s answer to concerns about cooling demand was an $80 million plant to recycle treated wastewater, designed for up to 13 million gallons a day. Work on it was paused in April 2026. After meeting the company, the City of Memphis said in June that SpaceXAI had committed to resume construction no later than the first quarter of 2027. Until it runs, the cooling water question stays open.

Colossus is also where Anthropic enters the picture. SpaceX’s prospectus says that in May 2026 it signed agreements giving Anthropic “access to compute capacity across COLOSSUS and COLOSSUS II”, about 325,000 NVIDIA GPUs, with a monthly fee through May 2029 (pp. 13 and F-62). Anthropic’s own S-1, filed in October 2026, puts its commitments to SpaceXAI at up to $120.5 billion over terms running into 2029. Neither filing says which building runs which workload. What they do establish is that a growing share of Claude’s compute sits on the infrastructure described above, which I cover from Anthropic’s side in the Claude audit.

Colossus II, Southaven, and the Clean Air Act Case

On 14 April 2026 the NAACP and its Mississippi State Conference sued X.AI Corp. and its subsidiary MZX Tech in federal court in northern Mississippi. The suit, brought with the Southern Environmental Law Center and Earthjustice, argues that the mobile gas turbines powering the Southaven site are stationary sources that need Clean Air Act permits. The plaintiffs count 27 turbines and estimate their potential at more than 1,700 tons of nitrogen oxides a year, from a site half a mile from homes and a mile from an elementary school. Nitrogen oxides are a main precursor of ground-level ozone.

SpaceX disputes the claim. Its filings describe the turbines as running with the permission of Mississippi’s environmental regulator, and the prospectus says “we have obtained such permits”, while warning that an injunction or rescinded permits “would prevent our ability to utilize power generation sources that are required for the operation of these data centers” (pp. 48-49).

The case has drawn in the federal government. According to SpaceX’s third-quarter report, the NAACP asked for a preliminary injunction on 6 May, which the company opposed. The United States moved to intervene in order to have the case dismissed, and the State of Mississippi filed a brief opposing the injunction. When the district court did not rule on the intervention, the United States appealed to the Fifth Circuit in September and asked for the case to be paused. On 19 October 2026 the Fifth Circuit rejected the appeal as premature, and the district court allowed the United States to join the case but declined to let it dismiss it. SpaceX’s report records no ruling yet on the injunction request.

The same report discloses a separate matter. In August 2026 Mississippi’s Department of Environmental Quality issued notices of violation to MZX Tech for starting construction before the sites were covered by the state’s stormwater permit, with penalties of up to $25,000 a day and a preliminary exposure of about $6.1 million across three sites. SpaceX says it is cooperating and seeking a single agreed order.

For a procurement lead, this is the most concrete environmental fact attached to any AI product today. It is documented, in court, and tied directly to the infrastructure that trains and serves Grok.

How Efficient Is Grok Per Query?

xAI’s efficiency claims are about tokens and price. When it released Grok 4 Fast in September 2025, it said the model matched Grok 4 on benchmarks using 40% fewer thinking tokens on average, for a 98% lower price to reach the same performance. Fewer tokens usually means less computation per answer, so the direction is plausible. Price is not energy, though, and xAI publishes no energy figure for any Grok model.

Even a real per-query gain changes little here. Independent rankings of per-query energy shift with every model generation, and the infrastructure underneath stays the same. A more efficient Grok still runs in data centres that SpaceX describes as powered mostly by its own gas generation. The per-query number is the small story. The power plant is the big one.

Why the Disclosure Floor Is So Low

SpaceX’s filings meet federal requirements as they stand. In March 2025 the SEC voted to end its defence of the federal climate disclosure rules, so what a US prospectus says about climate rests on the company’s own view of what is material. Qualitative risk factors and a list of lawsuits satisfy that standard. Quantified emissions are not required, and SpaceX has not volunteered them.

California’s SB 253 is the law that will eventually require numbers. It applies to US companies with more than $1 billion in annual revenue that do business in California, and SpaceX builds rockets in Hawthorne and runs its AI operations from Palo Alto (pp. 203 and 211). The first reports of Scope 1 and 2 emissions are due by 10 November 2026. But CARB’s guidance for this first cycle says that companies which were not collecting emissions data when its December 2024 enforcement notice was issued “are not expected to submit Scope 1 and 2 reporting data” this year, and asks them for a statement of non-reporting instead. The first SB 253 cycle may therefore pass without a single figure from SpaceX. The realistic date for mandatory numbers is the 2027 cycle, when Scope 3 reporting also begins.

What Grok Users Should Weigh

If you use Grok through X or through the xAI API, three things belong in the decision.

• Where the inference runs. Grok is trained and served from the Colossus cluster, and SpaceX’s own filings describe its power as mostly self-generated from gas. There is no per-token emissions figure, so any estimate you make rests on assumptions about turbine efficiency and grid share.
• Legal and reputational exposure. The Clean Air Act case and the stormwater notices are public record. If your organisation has a sustainability committee or reports on its suppliers, a Grok choice will need more documentation to defend than most alternatives.
• Timing. Waiting for California numbers is unlikely to help before the 2027 reporting cycle. Today’s evidence base is the prospectus, the quarterly reports and the court record.

Five Questions to Ask xAI, or Any AI Lab

1. Do you publish Scope 1, 2 and 3 emissions with third-party assurance? For xAI, a Scope 1 figure for its own turbines would be the easiest place to start.
2. Where will my workload run, and what powers that site? Ask for the share of on-site gas, grid supply and renewable contracts at the specific facility.
3. How much water do your sites use, and from which source? In Memphis, ask when the recycling plant will run.
4. Do you publish energy per model, or per thousand tokens? A price reduction is not an energy figure.
5. Are any of your facilities subject to environmental litigation or enforcement? Ask for the status in writing, and keep the answer in the procurement file.

Most labs will answer few of these in writing, and that gap is itself the finding. For xAI, the fifth question already has a public answer, and it should be in the file whatever the vendor says.

What Better Disclosure Would Look Like

The bar I hold every lab to in this series has five parts, and xAI meets none of them today.

• Assured Scope 1, 2 and 3 emissions. xAI’s Scope 1 should be straightforward, since it owns the turbines that produce most of its power.
• Energy, water and carbon per model. Grok 4 Fast’s efficiency claims would mean more with an energy figure behind them.
• The power mix by facility. The prospectus says “almost entirely” on-site and “primarily” gas. The percentages are the missing piece.
• A time-bound climate target. There is none at SpaceX or xAI level.
• Environmental disclosure alongside major deals. The $2 billion turbine purchase and the Anthropic capacity agreements both changed the footprint, and neither was announced with any environmental figures.

Where I’ve Landed

If a client asked me whether to build an internal workflow on Grok, my default for sustainability-sensitive work would be no. Grok is a capable model, and its per-query efficiency claims are plausible. The issue is that the vendor’s own filings describe gas-powered infrastructure in active environmental litigation, with no emissions data to set against it. The documentation burden of defending that choice is higher than for any other frontier lab.

I’d add two caveats. First, the gap with other labs is narrower than it looks, because Anthropic now buys capacity on the same Colossus cluster and OpenAI’s Stargate also runs partly on on-site gas. Second, the court case will move, and an injunction or a settlement could change the Southaven picture quickly. I’ll revisit this audit when the injunction is decided or when SpaceX publishes its first emissions figures, whichever comes first.

Frequently Asked Questions

Is Grok bad for the environment?

Nobody can quantify it, because xAI publishes no emissions or energy data. SpaceX’s filings say its AI data centres rely significantly on natural gas, mostly from its own on-site generation, and the turbines at its Southaven site are the subject of a Clean Air Act lawsuit.

Does xAI publish a sustainability report?

No. Neither xAI nor its parent SpaceX publishes a sustainability report, emissions inventory or climate target. The closest primary sources are SpaceX’s June 2026 prospectus and its quarterly reports.

What powers the Colossus data centres?

Mostly natural gas. SpaceX says both Colossus sites were brought online almost entirely through on-site generation it built itself, and that Colossus II can run entirely on its own gigawatt-scale gas power plant, with some grid supply and Megapack batteries alongside.

Is the xAI turbine lawsuit still going?

Yes. On 19 October 2026 the court allowed the US government to join the case but refused to let it dismiss the suit, and the NAACP’s request for a preliminary injunction against the Southaven turbines had not been decided at the time of SpaceX’s latest quarterly report.

The same audit applied to the other labs is in Is ChatGPT Sustainable? and the Claude audit linked above, and the synthesis with Google is in the generative AI piece. Each uses the same five disclosure tests, so the answers can be compared directly.

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Vetting AI vendors on environmental grounds? I run these footprint audits with the same rigour I bring to a materials audit. If your team is working out which AI tools it can defend in a sustainability review, that is the work I do. See how I work.