Electricity demand is forecast to exceed committed supply Thursday from 7 p.m. to 9:30 p.m., according to preliminary data from the grid operator late Thursday morning. The gap between supply and demand will be “more tight than any other day” this summer, Vegas told commissioners.

The expected tight conditions come due to very high heat, very high demand and the low expected output of wind power in the late afternoon as solar resources ramp down with sunset, Vegas said.

Natural gas and coal plants, which can underperform or fail in high heat, are seeing “at or near normal forced outage levels,” Vegas said. Grid data showed approximately 6,800 megawatts of natural gas and coal outages as of 11:30 a.m. Going into the summer, ERCOT predicted that natural gas and coal plants would see “typical” outages of 5,034 megawatts.