EXPLAINER: Why the power grid failed in Texas and beyond

DALLAS (AP) — The power outages tormenting Texas in uncharacteristically Arctic temperatures are exposing weaknesses in an electricity system designed when the weather's seasonal shifts were more consistent and predictable — conditions that most experts believe no longer exist.

This isn't just happening in Texas, of course. Utilities from Minnesota to Mississippi have imposed rolling blackouts to ease the strain on electrical grids buckling under high demand during the past few days. And power outages have become a rite of summer and autumn in California, partly to reduce the chances of deadly wildfires.

But the fact more than 3 million bone-chilled Texans have lost their electricity in a state that takes pride in its energy independence underscores the gravity of a problem that is occurring in the U.S. with increasing frequency.

WHAT HAPPENED IN TEXAS?

Plunging temperatures caused Texans to turn up their heaters, including many inefficient electric ones. Demand spiked to levels normally seen only on the hottest summer days, when millions of air conditioners run at full tilt.

The state has a generating capacity of about 67,000 megawatts in the winter compared with a peak capacity of about 86,000 megawatts in the summer. The gap between the winter and summer supply reflects power plants going offline for maintenance during months when demand typically is less intense and there's not as much energy coming from wind and solar sources.

But planning for this winter didn’t imagine temperatures cold enough to freeze natural gas supply lines and stop wind turbines from spinning. By Wednesday, 46,000 megawatts of power were offline statewide — 28,000 from natural gas, coal and nuclear plants and 18,000 from wind and solar, according to the Electric Reliability Council of Texas, which operates the state’s power...