Data center developers are turning to bespoke natural-gas power plants, a shift that stands to sharply increase carbon emissions and make it harder for US technology companies to meet their lofty climate goals.

Ninety-nine proposed plants tracked by BloombergNEF would emit about 318 million metric tons of carbon dioxide annually if run at industry-standard rates, according to a Bloomberg News analysis. The entire US electric power industry emitted about 1,485 million metric tons of carbon last year, according to Energy Information Administration data — meaning a single slice of data center infrastructure has the potential to lift US power-sector emissions by 20%, and by as much as a third should the new plants run flat out. US power-sector emissions had been declining for most of the past two decades as coal plants retired and wind and solar generation expanded, a trend the proposed gas buildout runs against.

The data center building boom has already strained the US electricity system, prompting reliability concerns and moratoriums on new project approvals. The strain marks a turn for a grid whose demand was broadly flat for two decades; researchers at Lawrence Berkeley National Laboratory estimated that data centers consumed about 4% of US electricity in 2023 and could account for as much as 12% by 2028. With even greenlit facilities facing yearslong delays connecting to regulated electricity grids, developers are seeking alternatives. These include so-called behind-the-meter projects that can be permitted and built without the approval of utilities or the independent system operators charged with ensuring grid reliability.

“There is immense, immense pressure on the whole sector to get power, and get it fast,” said David Pomerantz, executive director of the Energy and Policy Institute, a utility watchdog that promotes renewables. “They’re sort of agnostic if it is clean or dirty.”

Not all of the proposed plants in the BNEF data are likely to be built. The rush to capitalize on AI developers’ seemingly bottomless demand for computing power has produced some phantom projects and long-shot pitches.

Bloomberg’s estimate of likely emissions is based on 126 gigawatts of total planned on-site gas generation capacity tracked by BloombergNEF, an energy research firm owned by Bloomberg LP. The carbon footprint was calculated using a range of usage from an industry average of 60% to 100% for round-the-clock deployment, and a gas burn rate of a typical single-cycle gas generator. Emissions will vary depending on the use and the fuel-efficiency of the generator. A single-cycle model is now one of the most common types planned, although it is dirtier than the combined-cycle plants that data center developers want but are struggling to get owing to a yearslong backlog for turbines. The handful of global manufacturers that build large gas turbines — led by GE Vernova, Siemens Energy and Mitsubishi Power — have reported order books stretching years out as utilities and data center developers compete for machines.

The BNEF data includes projects backed by the leading AI labs, OpenAI and Anthropic PBC, upstart data center operators that fashion themselves as AI specialists, as well as cloud-computing giants and investor groups seeking tenants.

The projects tracked by BloombergNEF are spread across 22 states, from Alaska to Georgia. More than a third of them are in Texas, where ample oil and gas resources and a historically forgiving regulatory environment have had developers rushing to erect data centers as fast as they can be built and powered. Texas Governor Greg Abbott recently announced a pause in data center approvals.

The Texas projects include plants backed by Amazon.com Inc. and Microsoft Corp., the largest sellers of rented computing power and data storage.

Earlier this month, Cleanview, which tracks US power infrastructure and data center development, identified Amazon as the developer of an 8,000-acre site in Pecos County, which will become among the biggest single sources of carbon pollution in the US.

About 30 miles (48 kilometers) to the west, past a pecan orchard and scrublands dotted with oil derricks, Chevron Corp. is building Microsoft a gas plant to power a new data center complex on a 2,000-acre site.

The two plants alone could generate more than 10 gigawatts of electricity — enough to power New York City on a hot summer day. Their combined annual emissions may be as high as 45 million metric tons of carbon dioxide equivalent, according to regulatory filings. That is slightly less than half the cumulative emissions of Washington state, where both companies are headquartered.

That fossil-fuel infrastructure threatens to push Big Tech’s climate goals out of reach. Both Amazon and Microsoft are big backers of clean energy projects and have said they aim to zero out their contribution to the carbon emissions responsible for a warming planet. Microsoft has pledged to become carbon negative by 2030, and Amazon’s Climate Pledge commits it to net-zero carbon by 2040. Both companies have disclosed rising emissions in recent sustainability reports as they expand AI infrastructure, with Microsoft saying its footprint was up roughly 30% from 2020 levels, driven largely by data center construction. Those pledges were made before the artificial intelligence boom, at a time when technology companies were under pressure from employees and outside activists to do more to cut their emissions. Spokespeople for Amazon and Microsoft say their climate goals haven’t changed. Amazon is exploring its options for solar power and battery storage at the west Texas site.

“It has been a remarkable shift in the last three years,” said Drew Wilkinson, a former Microsoft employee who organized his colleagues to advocate for tougher sustainability measures. “The companies who set the bar for corporate climate action are now bringing net new fossil infrastructure online at a breakneck pace. Few of us saw it coming.”

To contact the authors of this story: Matt Day in Seattle at mday63@bloomberg.net; Mark Chediak in San Francisco at mchediak@bloomberg.net.

This story was originally featured on Fortune.