Colossus 1 & 2 — xAI's Memphis Gigawatt Campus

1 · The speed record

When xAI acquired the former Electrolux manufacturing plant in South Memphis in early 2024, no one believed the timeline. Elon Musk promised a working 100,000-H100 cluster by late summer. That's roughly the largest single-site GPU installation ever built, and it would normally take 18–36 months.

Colossus came online on schedule: 122 days from construction start to first training run(July 2024). Within three months of the original milestone, xAI doubled capacity to 200,000 GPUs — a mix of H100s and H200s. By early 2026 the company was publicly targeting 1 million GPUs across the combined Memphis + Southaven footprint.

2 · Power — the controversial part

A 250 MW AI campus in 2024 exceeded every available slot in the Memphis Light, Gas & Water (MLGW) interconnection queue. xAI's answer: build its own substation, and in the meantime, run gas turbines.

The substation

xAI paid $35M to finance a 150 MW MLGW substation — the first time in modern memory a tech company directly financed utility-grade infrastructure. The build took 97 days versus the typical 2.5 years. A second substation is now being built at an additional $20M cost.

The turbines

To bridge the gap, xAI installed 35 gas turbines generating 420 MW on the Colossus 1 site. The regulatory trick: Shelby County only requires air permits for generators in place more than 364 days. xAI initially ran them as "portable" — unpermitted.

The Southern Environmental Law Center, representing the Memphis NAACP, filed Clean Air Act notices — but the turbine fleet grew rather than shrank (from ~27 to 33+). In January 2026 the EPA revised its New Source Performance Standard so that large methane turbines require permits even for temporary operation. The dispute then escalated: on April 14 2026 the NAACP and Earthjustice filed a federal Clean Air Act lawsuit against xAI, followed by a motion for a preliminary injunction in May 2026.

For Colossus 2 in Southaven, Mississippi, xAI installed 33+ gas turbines (Mississippi regulators permitted 41 in March 2026), roughly 500+ MW — equivalent to a small conventional power plant. Total announced air emissions: on the order of 1,200–2,000 tons of NOx per year from Colossus 1 alone, likely making it the largest industrial NOx emitter in Memphis.

The long-term plan

Turbine permits expire in 2027. By then xAI expects to rely on two MLGW substations, a 500-acre solar farmunder planning near the site, and 168 Tesla Megapack units (150 MW total) for grid-decoupling battery storage.

Source: Shelby County Health Department permit filings · SELC / NAACP Clean Air Act notices of intent · MLGW press materials · SemiAnalysis "Colossus 2: First Gigawatt Datacenter" (Dylan Patel, Jan 2026) · Solaris Energy Infrastructure investor disclosures (NYSE: SEI).

3 · Silicon — the rental-fleet trick

Public fact: Colossus began with 100,000 H100 SXM5s in custom liquid-cooled Supermicro chassis. Expansion phases added H200 and (reportedly) GB200 NVL72 racks.

A less-publicized fact worth understanding: NYSE-listed Solaris Energy Infrastructure owns a 600 MW rental fleet of gas turbines, roughly 400 MW of which currently serves xAI. Of Solaris's 1,700 MW order book, 67% is committed to xAI — ~1,140 MW total, with 240 MW at Colossus 1 and 900 MW going into a 50.1/49.9 Solaris-xAI JV. By Q2 2027, Solaris expects over 1.1 GW of operating turbines serving xAI.

This is novel infrastructure finance: xAI gets gigawatt-scale firm power without waiting for utility interconnect, and Solaris gets long-term baseload contracts on owned assets. It's effectively bring-your-own-power as a service — a model that didn't exist 18 months ago.

4 · Cooling — direct liquid, from day one

Colossus 1 was built with direct liquid cooling (DLC) on the H100 cold plates from the start. The facility loop returns to a central mechanical yard with dry coolers, reflecting Memphis's hot-humid climate (~2,200 free-cooling hours/year). PUE disclosures are not public but analyst estimates put it around 1.20–1.25, typical for DLC deployments in that climate.

5 · Lessons from Colossus

• Speed is an engineering discipline. Parallel permitting, parallel substation + building construction, custom chassis design ordered before the first GPU shipment. xAI did not invent new physics — they removed every sequential dependency.
• Self-generated power is the new escape hatch. When the grid queue is 5+ years, on-site turbines win over compliance. The environmental and political cost is real and pending.
• Environmental approval is a cost, not a blocker. The NAACP + SELC campaign forced turbine removal and an EPA rule change, but Colossus still ran for 18+ months unpermitted. The playbook seems to be: build now, litigate later.
• Rental turbines + batteries is the bridge. Until substations and solar come online, xAI is paying Solaris to rent firm power. Worth studying as a financial model for other latecomers to the grid queue.