ERCOT's 218 GW Forecast Is Mostly Data Centers on Paper, So It Wrote a Discount

The forecast that Texas transmission utilities handed ERCOT this year would more than double the grid's size in six years. In materials for its April board meeting, ERCOT showed a utility-provided long-term load forecast that climbs to 218 GW by 2031. Most of the growth is new data center load, and most of that is supported not by signed contracts but by letters from utility officers attesting that the load is coming. It has built an adjusted forecast that applies discounts drawn from its own experience of how much requested load actually shows up, and when.

ERCOT's board presentation explains that its forecast process changed because of state law. Data center growth for 2030 alone rose from 29,614 MW in the 2024 forecast to 77,965 MW in the 2025 forecast. ERCOT's adjusted method applies three corrections, each based on what has actually happened on its grid. First, it delays the in-service date of all new contract and officer letter loads by 180 days. Second, it reduces all new data center demand to 49.8% of the requested amount.

Third, it reduces all officer letter loads to 55.4% of the request, which is the share of projects with 2024 in-service dates whose load was in service by February 2025. ERCOT notes that these factors can be updated as more contract and officer letter loads are energized. The long-term forecast report ERCOT published on April 8 puts numbers on the adjusted path. ERCOT will use the adjusted forecast for its Capacity, Demand and Reserves report starting in May, with the utility-provided forecast shown as a comparison scenario.

The distinction matters because demand forecasts drive transmission spending, reserve margins and price signals. Set against a forecast that adds more than 120 GW in six years, those historical rates look small. The officer letter rule was meant to keep ERCOT's planning from lagging behind real demand.