Data Centers: Power Plants & Emissions

Several data center projects in Iron County and nearby Millard County plan to make their own electricity on site with natural gas engines or turbines. This page collects what the public filings say. Updated October 27, 2026.

Map

Oct 26, 2026: The Iron County Commission voted to repeal the data center moratorium and adopt new data center rules (Salt Lake Tribune, Oct 27, 2026). The moratorium is no longer in effect.

Topographic map of Iron County data center sites with towns, landmarks, the Three Peaks Recreation Area and power infrastructure, updated October 27, 2026 — Data center sites, towns, landmarks and power infrastructure. The Iron County Shooting Range location is approximate (from a shooting-club website; the county describes it as about 15 miles northwest of Cedar City). Three Peaks Model Port and the Three Peaks RC Track are placed from BLM site pages. Sources: Iron County planning page; Utah Public Notice Website minutes; St George News; KUER; Salt Lake Tribune; USGS 3DEP elevation; USGS GNIS; UGRC roads; BTS rail; OpenStreetMap contributors (ODbL); BLM. Click the map for full size.

Where people live

Map of Iron County 2020 Census population density by block, with data center sites and 5, 10 and 20 mile rings — Population density by 2020 Census block, with 5, 10 and 20 mile rings around each site. Town totals are summed from Census blocks inside each place boundary. Sources: U.S. Census Bureau, 2020 Census P.L. 94-171 block population and TIGER/Line 2020 boundaries; Iron County GIS site parcels; UGRC roads. Computed

Nearest residents

Map of populated 2020 Census blocks nearest the Iron County data center sites, with a table of straight-line distances — Populated 2020 Census blocks near the sites, with straight-line distances from each site to nearby communities and scattered homes. One Census block can cover scattered homes over several square miles. Sources: U.S. Census Bureau 2020 Census P.L. 94-171 block population and TIGER/Line 2020; USGS GNIS place names; Iron County GIS site parcels; UGRC roads. Computed

Engine counts by site

Site	County	Gas engines	Diesel backups	Status	Source
Antelope (Pronghorn)	Iron	90 or 120 Verified	Some; count not stated	County approved Jun 4, 2026; appeal pending; no air permit filing	Iron County Planning Commission minutes, Jun 4, 2026 (5 buildings × 18) and Mar 5, 2026 (5 × 24)
Red Butte (BrightNight)	Iron	0 or 44 Wärtsilä. The engines are one of three options; the other two use turbines. Third-party copy Unverified	4 (2 generators, 2 fire pumps)	Air application not on the state status list	Air permit application dated July 3, 2026 (third-party copy)
Juniper	Iron	Not published	Not published	No filing found	Developer site
Joule Capital, Site 1	Millard	69 Verified	69	Permitted Jan 22, 2026 (~175 MW)	Utah DAQ DAQE-AN162810001-26
Joule Capital, Power Station 5	Millard	69 Verified	69	Permitted Sep 11, 2026	DAQE-AN162930001-26 (third-party copy; listed on the state permit status list)
Joule Capital, Sites 2, 3, 4, 6	Millard	Not verified Unverified	Not verified	Permitted Sep 11, 2026	State permit status list

Totals Computed

Iron County gas engines only: 90 to 164
Iron and Millard gas engines: 228 to 302
Gas and diesel engines at verified sites: 366 to 444

These totals don't count Juniper, Antelope's backup generators or Joule Sites 2, 3, 4 and 6, because those counts haven't been published or verified.

Permitted and proposed emissions (tons per year)

Pollutant	Joule Site 1 (69 engines) Permit	Red Butte: 15 Siemens turbines	Red Butte: 20 PE6000 turbines	Red Butte: 44 Wärtsilä engines
Nitrogen oxides (NOx)	230	233	237	248
Carbon monoxide	203	247	239	210
Volatile organics	107	135	139	178
Fine particulates	61	177	248	145
Hazardous air pollutants	126	10	not extracted	50
Formaldehyde	69	4	not extracted	20
Greenhouse gases (CO₂e)	865,632	2,036,706	2,387,084	630,928

The Red Butte figures come from the July 2026 application Third-party copy, which the state hasn't reviewed yet. Antelope has no air filing, so it has no emissions figures. Sources: Joule permit; Iron County Antelope Q&A.

Per-engine limits (Joule Site 1 permit) Verified

NOx: 0.06 g/hp-hr · CO: 0.08 g/hp-hr · VOC: 0.07 g/hp-hr
Diesel backup generators: 50 hours a year of non-emergency use

Pattern: just under 250 tons of NOx

Every permitted or proposed configuration lands just under 250 tons a year of NOx (230 to 248). 250 tons a year is the major-source threshold that triggers federal Prevention of Significant Deterioration (PSD) review for most source types. Joule's 126 tons a year of hazardous air pollutants is over the 25-ton combined threshold, so it's a major source for those pollutants.

Carbon intensity Computed

From the greenhouse gas totals and plant capacity, our estimate is roughly 1,100 to 1,200 lb CO₂ per MWh for both Joule and Red Butte. That's in the upper part of the 800 to 1,250 lb/MWh range of the federal standards for gas plants. This assumes the plants run at full capacity all year.

Cooling and lubricating oil

Permits: the permits don't describe engine cooling design or lube-oil storage. The only cooling equipment listed is Joule's 69 boiler-chillers, which make chilled water. Verified
Red Butte application: two 2-million-gallon diesel fuel tanks (fuel, not lube oil). Third-party copy
Wärtsilä 50DF (vendor figures): separate high- and low-temperature water cooling circuits, about 550 L of oil in each engine and an 8 m³ oil system tank per engine. Vendor figures
Caterpillar G3520 (vendor figures): about 143 gal of oil, changed about every 1,000 hours. Vendor figures
Estimates Computed: 44 Wärtsilä engines ≈ 93,000 gal of system oil; 69 G3520-class engines ≈ 10,000 gal per oil-change round. Which engine model Joule uses isn't stated here.

Gaps in the public record

Joule's gas engines have no annual run-hour limit.
No permit addresses what happens to the power plant if its data center closes.
Antelope hasn't filed for an air permit, so it has no emissions numbers.
Juniper's engine count, and the counts for Joule Sites 2, 3, 4 and 6, haven't been published or verified.
No staffing or water-use figures were found for any site.