Gas-fired plants planned for AI data centers could push US power-sector carbon dioxide emissions up by roughly two fifths over the 2025 level by 2030, according to an internal analysis by the Sierra Club that Bloomberg reported on 28 October. The group says that would wipe out about fifteen years of reductions. It is a projection built on announced projects, not a measurement, and the authors of the report are open about how far the estimates spread.
Most of it is outside the grid
The split matters more than the headline. In the Sierra Club's numbers, generators connected to the grid add a modest share, around a tenth, to the 2030 baseline. The larger part comes from plants that tech companies build for themselves to avoid waiting for a grid connection, and the group's estimate for those alone is comparable to a whole country's yearly emissions, with Mexico used as the yardstick. Earthjustice and the Better Data Center Project estimate that about four fifths of that self-supplied energy could come from gas. Cheap gas and the rollback of federal climate rules are named as reasons the power sector's emissions already turned up in 2025.
How much weight the number can carry
Other projections sit well below it. The Union of Concerned Scientists expects a rise of one fifth to somewhat more than a quarter by 2035, a journal article from June lands at about a quarter, and the most emission-heavy scenario from Rhodium Group still ends 2040 below today's level. The Sierra Club itself says its estimates have grown sharply in the last year and a half. The spread between the lowest and highest published forecasts is larger than the electricity use of California and Florida together.
What decides it is unknown: how many campuses are really built, what they burn, how much renewable supply arrives in time. Turbine backlogs and slow grid connections can delay or stop projects, and Oracle has already warned that a New Mexico site may miss its 2028 target. A BloombergNEF analyst says a large growth in gas power would be expected to raise emissions, while another analyst quoted says the outcome is not a foregone conclusion.
What it changes at the permit desk
Whatever the final figure, regulators will read it as a reason to look harder at on-site plants. A plant that runs all year is judged on annual emissions, not on a few hours of testing, and the questions that follow are about exhaust treatment, fuel and recorded running hours. We looked at the same pressure from the air-quality side in the Texas report. Teams planning backup or bridging power should expect those questions before the first drawing is approved.
Sources: Bloomberg via Claims Journal, Energy Connects