Unprecedented winter storms have hit Texas so hard and forced so many power plants offline that rolling grid outages that began Sunday night have grown into hours-long blackouts leaving about 2.5 million customers without power on Monday morning. Until those power plants can be brought back online, it’s unclear how many people will be left powerless and for how long.
That’s the dire report from Texas grid operator ERCOT after its supply-demand balance grew much worse than expected through Sunday evening and into Monday morning. The historic storm that spurred a statewide emergency declaration from Gov. Greg Abbott on Friday has forced power plants and wind farms to stop generating electricity, triggering statewide emergency blackouts and leaving the timeline for restoring that power unclear.
Texas has become the epicenter in a series of winter storms that has blanketed the central U.S. and spurred storm watches in 40 states. ERCOT hit a record winter peak demand of about 69.2 gigawatts on Sunday evening. Demand for electricity to heat and power homes, businesses and factories remained high through the evening and into Monday morning, Dan Woodfin, ERCOT’s senior director of system operations, said in a Monday press conference.
At the same time, a number of natural gas, coal and nuclear thermal generators began tripping offline starting around 1:30 a.m. Monday, he said. While ERCOT hasn’t yet collected the data to determine the precise causes of those generator outages, a previous report from a 2014 cold snap suggests a range of causes, from natural-gas pipelines freezing up to the failure of equipment that's needed to keep power plants operating safely.
ERCOT has been working with generators for a decade to improve winterization practices to forestall these kinds of cold-related outages, Woodfin said. Similar efforts to ensure an adequate level of supply amidst cold snaps have been instituted in the U.S. Northeast following the "polar vortex" storms seen over the past decade. But the unusual severity of the storm meant ERCOT's efforts were not enough, according to Woodfin.
“This event was well beyond the design parameters for a typical, or even extreme, Texas winter that you would plan for,” he said. “This weather event is really unprecedented — all of us who live here know that.”
Rapidly falling temperatures and storms of a ferocity that Texas hasn’t seen since the 1940s also forced some of the state’s ample wind power resource to go offline due to icing of wind turbine blades, he said. But thermal power plants made up the majority of lost supply, he said.
In total, about 34 gigawatts of generation capacity were unavailable as of Monday morning.
UPDATE: It's also possible that constraints in natural-gas supplies for generators may be forcing plants to go offline. Jesse Jenkins, a Princeton engineering professor at the Andlinger Center for Energy and the Environment, noted in a Monday tweet that sources have indicated to him that roughly 26 gigawatts of the generation capacity forced offline overnight consisted of natural-gas plants unable to procure fuel that's being directed to heating needs.
From rolling blackouts to widespread outages, with an uncertain restoration timeline
This rising loss of generation forced ERCOT to take emergency measures, maintaining enough reserve capacity to ensure that its entire grid didn’t collapse, according to Woodfin. Those escalated from voluntary conservation requests and seeking electricity imports from outside the state to its final “energy emergency alert three” call to the state’s transmission utilities to start powering down portions of their grids early Monday morning.
“At our highest point, we asked transmission operators to reduce 16,900 megawatts of load,” Woodfin said. While these load reductions are meant to be executed as “rolling blackouts” that rotate between portions of their grids for between 15 to 45 minutes apiece, the scale of the gap between supply and demand has forced utilities to extend the duration of outages for hours in order to avoid blacking out sections of the grid serving hospitals, police and fire stations and other critical facilities.
The outages have affected major utilities such as CenterPoint, Oncor, Entergy, Texas-New Mexico Power and American Electric Power Texas, as well as municipal utilities such as Austin Energy and San Antonio’s CPS Energy, and the rural electricity cooperatives that serve large swaths of the state.
The central part of the state appeared worst affected as of Monday morning, according to data from tracking site PowerOutage.US. Oncor, which serves the greater Dallas/Fort Worth area, reported more than 1 million customers without power, while AEP reported more than 300,000, and Austin Energy and CPS about 200,000 apiece.
The Midcontinent Independent System Operator also instituted emergency load reductions in its southeast Texas territories on Monday, and Southwest Power Pool (SPP) requested similar rolling outages from utilities in Oklahoma and the Texas panhandle.
The scale and duration of Texas’ winter outages are far greater than those that California grid operator CAISO was forced to institute during a regionwide heatwave in August, which affected several hundred thousand customers for about an hour over two consecutive evenings. While a handful of natural-gas generators were taken offline during that emergency, the state was able to call on voluntary conservation and additional supplies to prevent rolling blackouts later that summer. California regulators are scrambling to bring more grid capacity online to avoid similar emergencies this summer.
ERCOT’s energy-only wholesale electricity market has been able to pull in demand response and other sources of grid flexibility during less harsh cold snaps and summer heat waves in past years. But the scope of the current storm, and the scale of generators going offline, has overwhelmed those resources.
As of mid-morning Monday, “we’ve seen a slowdown in the number of generators that have been tripping offline,” Woodfin said, which gives hope that more generators will be able to be brought back onto the grid to restore power to more customers.
“We don’t think these outages will be multiday outages,” he said. “We hope they’ll be able to come back in a matter of hours.” But, Woodfin added, “that’s completely dependent on the amount of generation that’s available.”