Texas squeezed by on Tuesday with just enough electricity to keep the lights on. On Wednesday, it will face the prospect of blackouts all over again.
Temperatures are expected to reach 37 degrees Celsius in Houston as a heat wave that's expected to drag on through the end of the week blankets the western half of the US. The extreme weather is testing Texas's power grid just four months after a freak winter storm blacked out millions of people across the state and left more than 150 people dead.
Another hot day is expected today, with locations all across North & Central TX expected to warm into the mid to upper 90s this afternoon.
The searing weather marks the first heat-related stress tests of the year for U.S. electricity grids as a historic drought grips the western half of the nation. It comes nearly one year after California witnessed its own rolling blackouts during a heat wave last summer.
The Texas grid operator said Tuesday afternoon local time that its system remained stable despite crushing demand. It reported having about 3.4 gigawatts of power reserves, representing a extra-supply margin of about 10%. Spare capacity had grown to nearly 8 gigawatts early Wednesday morning as temperatures dropped.
The Electric Reliability Council of Texas said it would call the first stage of a grid emergency should reserves fall below 2.3 gigawatts and would start rolling blackouts if they fell below 1 gigawatt.
The tight supply conditions came after generating plants with as much as 10.6 gigawatts of capacity -- enough to power about 2.1 million homes -- were unexpectedly down for repairs amid elevated demand. About two-thirds of those out of service are natural gas, coal and nuclear plants. The rest are wind and solar, the grid operator said.
California officials also warned that power demand could outstrip supply later in the week. Supplies could be tightest on Thursday, when demand could top 43 gigawatts, or about 3.4 gigawatts more than projected supplies, according to the California Independent System Operator, which manages most of the state's power grid.
Though it often relies on electricity from neighboring states during heat waves, this week's heat is expected to stretch clear to the Canadian border, limiting imports, the operator said.