Leaders say Texas has power reserves to meet summer electricity demands but experts not as optimistic

AUSTIN — With critics questioning whether legislation signed to reorganize the Electric Reliability Council of Texas’ leadership and overhaul the state’s electric grid is sufficient, state officials contend there’s another reason to be optimistic there will be enough power to meet demand through a long hot summer.

The state’s “summer reserve margin,” or generating capacity exceeding demand, is higher than last summer and should help avoid the blackouts that plagued Texas during February’s winter storm and set in motion the legislation to address the crisis.

“That’s why, if you look at the reports that ERCOT has out regarding summer capacity, that they feel very comfortable and that we’ll be able to meet the demands of summer,” said GOP Sen. Kelly Hancock.

In its summer forecast for grid conditions, ERCOT calculated that this summer’s reserve margin — the amount of capacity that exceeds demand — would be 15.7%. The bigger the margin, the bigger the cushion of supply is likely to be. The reserve margin is larger than last year’s and Warren Lasher, ERCOT’s senior director of system planning, has previously said that it will continue to grow, largely thanks to new renewable generation joining the grid.

State leaders have touted this summer’s increased power reserve margin as a reason to relax in the face of high summer demand, but experts say last week’s generation outages are evidence the reserve margin isn’t the safety net state leaders hope it to be.

Jim Boyle, a veteran utilities lawyer and consumer advocate who was the first head of the Office of Public Utility Counsel, explained that the calculation of reserve margin relies on several assumptions, several of which did not hold true last week, when ERCOT called on Texas to conserve energy to avoid forced outages.

The first assumption was that, on average, only 5% of thermal generation — which include nuclear, natural gas and coal-powered plants — would be down during outages. But 15% of the state’s thermal generation capacity was out last week, largely driven by unplanned repairs and maintenance, and by a fire at the Comanche Peak power plant that led to an outage of one of the plant’s two units. Each unit of the plant, owned by Irving-based company Vistra Corp. and located 60 miles southwest of Dallas. When both units are operating under normal conditions, they produce enough energy to power 1.15 million homes.

Boyle said 95% capacity is far too optimistic for a thermal fleet as old as Texas’, where nearly one-third of plants are older than 40 years.

“We have a lot of plants that are antique — they’re almost dinosaurs,” he said. “And that’s one reason that they have forced outages. We’ve got some very ancient coal plants, and we’ve got some very ancient gas plants that soon will be retired. We’ve got to work on our reserves.”

Wind also underperformed last week. ERCOT’s calculation of the reserve margin allows for variability in wind output between 19% and 61% of total generation capacity, but last week it was only producing 10% of total capacity.

“Winds were incredibly stagnant, so stagnant that Dallas had its worst smog day since 2007,” said Daniel Cohan, an atmospheric scientist at Rice University. “During some hours, wind output fell even below ERCOT’s worst case scenario.”

One assumption that did hold true was the output of solar generation. Solar was operating at about its forecasted output of 80% last week.

Using the grid’s voluntary load reduction resources — namely, asking customers to reduce their personal power consumption by raising thermostats, turning off lights and delaying loads of laundry — brought demand to below 70,000 megawatts on the afternoon of June 14, when the conservation notice was issued. That day’s peak demand was still about 7,000 megawatts less than ERCOT’s forecasted peak demand for the summer.