At one point during the afternoon, grid operator ERCOT — the Electric Reliability Council of Texas — warned there was a “high probability” of rolling blackouts.

Yet if the scorching weather should prompt ERCOT to call for wider rolling blackouts in the coming days, CPS and other utilities connected to the grid would be required to comply — and within 15 minutes, CPS spokeswoman Christine Patmon said.

CPS would not cut power to critical customers, such as hospitals and emergency services handled by the fire and police departments, she said, but residential customers would be affected.

Every degree a person lowers the thermostat below 78 adds an additional 7 to 10 percent to their electric bill as well as additional stress to the power grid.