The Houston Advanced Research Center, an independent nonprofit known as HARC, released an analysis on 20 October that puts air emissions at the centre of the Texas data center debate. Its finding, as the group summarizes it: meeting the new electricity demand could erase much of what the state has gained in air quality since 2002, by 2031 or sooner. How bad it gets depends mostly on where the power comes from.
What Texas Has to Lose
HARC's release says the Texas power sector cut nitrogen oxides by 68 % between 2002 and 2024 while population and economy grew. The group modeled three data center demand forecasts, from ERCOT, from the transmission service providers and from BAXTEL, and says data centers are expected to add more demand in the next six years than the grid added in the previous twenty.
With the anticipated grid mix, power-sector NOx rises 136 % from 2025 levels by 2031, which HARC says is close to the 2004 level. Volatile organic compounds end up 32 % above their 2002 level, and fine particulate matter returns to where it stood in 2006.
Engines on the Site, Grid at the Fence
The scenarios that matter most for readers in our business are the on-site ones. HARC modeled reciprocating engines burning natural gas as one option. Under the highest demand forecast, it says, annual NOx from such engines would exceed everything Texas emits today from all sources. Pollution controls bring that down, but controlled engines still emit about two to three times as much NOx as grid supply, according to the release. HARC's Carlos Gamarra put the gap at roughly four times for the same facility in the Texas Tribune's account.
The cleaner end of the range is a split: about a third of the power from the grid and the rest from on-site solar and wind, which HARC says cuts NOx and CO2 by about two thirds compared with grid-only supply. Even that case is above a Texas with no new data centers. Two assumptions are worth knowing: the model runs facilities at 80 % of capacity around the clock, and each scenario gives every new data center the same type of power. HARC itself notes that real sites may run lower and mix sources.
Why Developers Look at Engines at All
The Texas Tribune counts at least 288 data center projects planned in the state. ERCOT received more than 500 large-load connection requests in two years, against about two dozen the year before, and grid connection can take three to five years, which pushes developers toward generating on site. Governor Greg Abbott has temporarily halted new data center connections pending an audit, the Tribune notes.
The Data Center Coalition's Cameron Poursoltan told the paper the analysis may not reflect actual demand, and pointed to ERCOT officials who have called the forecasts likely overstated.
Prime Power Is Not Emergency Power, but the Permit Office May Not Care
The report is about engines that run as the main supply, not about emergency sets that run a few hours a year, and the Tribune says it does not address backup generators. In a permit file the two tend to blur anyway. Once a state agency has a study like this on its desk, an application for hundreds of engines will be asked for emission data, operating hours and controls, whatever the engines are called. Virginia already moved that way for new diesel units (our report). If you are quoting for a Texas site, have the engine emission documentation ready before the question comes.
Sources: HARC, HARC report page, The Texas Tribune