With triple-digit temperatures scorching the state, demand for electricity on the Texas power grid broke an all-time record Thursday for the second day in a row, according to preliminary figures from the state’s grid operator.

Demand across the Electric Reliability Council of Texas (ERCOT) service area reached 73,320 megawatts as of 4:39 p.m. Thursday, according to ERCOT data. That beat the previous record of 72,192 megawatts set between 4 and 5 p.m. on Wednesday.

“What you’re seeing is the extended period of triple-digit days,” ERCOT Senior Corporate Communications Specialist Leslie Sopko told the Rivard Report Thursday morning. “What drives load during the summer in Texas is the air conditioning.”

For a sense of scale, ERCOT’s peak forecast is around 15 times higher than San Antonio’s peak demand on Wednesday, according to CPS Energy figures.

CPS Energy is a municipally owned utility providing electric service to more than 821,000 customers in the San Antonio area. ERCOT, by contrast, coordinates the flow of electricity to most of Texas.

CPS Energy spokesman John Moreno said in an email that the utility’s demand peaked at 4,859 megawatts between 6 and 7 p.m., below its all-time record of 5,017 megawatts on Aug. 12, 2016.

“While CPS Energy did not set a record, we look for that to happen in the next few days,” Moreno said.

ERCOT’s energy load forecast for Thursday, July 19, 2018. Credit: Courtesy / ERCOT

On Wednesday, Abilene, Amarillo, Austin, Dallas-Fort Worth, El Paso, Lubbock, Midland-Odessa, San Angelo, Waco, and Wichita Falls were among the Texas cities that recorded high temperatures of 100 degrees or more, according to the National Weather Service. (San Antonio’s high was 99 degrees).

Forecasts are predicting temperatures of 103 degrees or more and heat indexes at or above 108 degrees, according to the San Antonio Metropolitan Health Department, which issued a heat advisory Thursday.

Demand commonly spikes in the late afternoon and early evening, both locally and at the state level.

“That’s basically when people are getting off of work and coming home turning their air conditioners on, turning on their stoves, and using their appliances,” Sopko said. “As the sun goes down, that load tapers off.”

ERCOT has had sufficient power flowing onto the grid to meet demand and is operating under normal conditions, Sopko confirmed. The grid operator does have options to reduce power use across the state if its reserves dip below a certain threshold.

CPS Energy did employ some of its own conservation measures on Wednesday to help reduce demand, Moreno said.

These measures include the My Thermostat Rewards program, in which participating customers get a free WiFi-enabled thermostat from the utility or an $85 rebate and $30 annual bill credit to offset the cost of installing a thermostat of their choice.

This allows CPS Energy to adjust its customers’ temperature settings during hot afternoons and other peak demands times. The utility recently rolled out a similar program that involves a partnership with smart thermostat manufacturer Nest Labs.

The utility also offers incentives for its commercial and industrial customers to curtail their electricity use, typically between 3 and 6:30 p.m. on weekdays.

In total, these and other similar programs can help the utility cut demand by up to 212 megawatts, Moreno said.

Brendan Gibbons is a former senior reporter at the San Antonio Report. He is an environmental journalist for Oil & Gas Watch.