On-site gas plants planned for U.S. data centers could add emissions equal to 10% of projected 2025 U.S. power-sector output if every announced project is built, BloombergNEF warned in a report released Wednesday. Bloomberg Philanthropies commissioned the study.

The finding turns on scale. Developers have proposed 181 gigawatts of gas-fired generation to serve data centers, and more than 90% of that capacity sits in the United States. Under BNEF's assumptions — every announced plant gets built and runs — the fleet would release roughly 345 million metric tons of carbon dioxide equivalent per year.

That figure is not a forecast. The pipeline contains projects at widely different stages and on different schedules, BNEF said, and signals how large the buildout could become rather than which projects will reach completion. The number still matters for planners: 345 million tons per year is 152 million tons higher than the emissions the same data center capacity would produce running on the typical U.S. grid mix — a gap of nearly 80% more carbon for the same computing work.

Why temporary plants may become permanent

Many of the projects exist to bridge a gap. Data center developers need power while they wait for grid connections that can take years, and gas turbines can be installed far faster than utilities can build transmission.

The risk comes after connection. Once on-site plants are running, the economics may favor keeping them online, creating what BNEF describes as a longer-term danger of locking in fossil fuel generation at facilities designed to serve demand that the grid could otherwise meet.

"The climate outcome will depend not only on how much electricity these facilities use, but on how quickly grids can connect them and whether power systems add cleaner generation alongside that demand," Mark Daly, head of data centers and emerging tech at BloombergNEF, said in a statement.

The demand driving the buildout is large and global. BNEF expects data center electricity consumption to reach 2,354 terawatt-hours by 2035 — about 7% of world electricity use.

Where on-site gas beats the grid

The report draws a geographic split. In the United States and Europe, BNEF found grid-connected data centers are the more sustainable option, and faster interconnections would cut both near-term emissions and lock-in risk.

In emerging markets, the calculus reverses. Where power systems depend heavily on coal, plugging into the grid can produce more emissions than running the same facility on on-site gas.

The U.S. problem, in BNEF's framing, is not grid quality but grid speed. "The grid performs well on reliability and cost and sustainability, but it has a major weakness: It fails on speed, and that's the one thing we care about today," Musfika Mishi, a BloombergNEF associate covering data centers and emerging technologies, said at the BNEF Summit in Houston, according to Bloomberg.

Can interconnection queues move faster?

Grid operators are already exploring ways to shorten the wait, Mishi said. Two options stand out:

• Processing interconnection applications more quickly
• Making flexible transmission service legal, so data centers can shift computing workloads to off-peak hours or reduce grid draw by leaning on backup generation during constrained periods

The flexible approach produces lower emissions than running on-site gas year-round, Mishi said — even when the backup runs on diesel.

The report leaves operators and utilities with a race: connect data centers to cleaner grids before the gas plants now on the drawing board become fixtures.