The new data sets shed new light on ERCOT’s surprising June 14-18 call for energy conservation that it issued statewide.


Many of the same plants that failed during the Winter Storm Uri freeze in February likewise suffered technical failures during a June power shortage — despite relatively mild weather conditions last month, according to newly released ERCOT data.

The data also confirm that unplanned outages among thermal plants — that is, outages at coal, natural gas and nuclear plants — significantly contributed to the electric shortage in June. Wind generators likewise accounted for a large number of the unplanned outages.

The new data sets, which can be found here, shed new light on ERCOT’s surprising June 14-18 call for energy conservation that it issued statewide. ERCOT said technical problems at a relatively large number of power plants prompted the conservation plea, and according to the new data, more than 225 unplanned outages were initiated during that five-day period. But lawmakers and others have called for more information.

Expedited Release

In response, the Public Utility Commission ordered ERCOT to begin releasing information about unplanned generation outages in an expedited fashion – that is, instead of its previous practice of releasing the information 60 days after an outage event,  ERCOT now must release it within 3 days. Last week ERCOT made its first disclosures under the new PUC rule, including disclosing data pertaining to its June 14-18 plea for conservation.

And while ERCOT’s new data fails to provide much guidance as to what prompted the unplanned outages, it does provide details about which plants went out of service during those five days and the length of their outages.

In all, more than 18,000 megawatts of generation went offline or partially offline during the five-day period, according to the data.  (A megawatt is roughly enough power for 200 homes on a hot summer day.) However, not all that power remained offline simultaneously — that is, some plants were unavailable or partially unavailable for less than a day, while other plants lost power for much longer periods. Some plants also went offline on multiple occasions.

Additionally, some major unplanned outages began prior to the five-day event, and continued forward into it. For instance, a 1,195-megawatt unit of the Comanche Peak nuclear plant in North Texas went offline of June 7, and did not return to service until June 17. Similarly, NRG’s Limestone Plant No. 2 — a lignite coal plant — reported an 836 MW outage on June 11 and a return-to-service date of June 21.

The new data shows 1,142 unplanned outages initiated during last month overall.  It also shows numerous unplanned outage events on each day of the month, with 20 to 40 reported on many days.

Other details

  • Approximately 70 percent of generators that reported unplanned outages beginning at various points June 12-17 — the period just before ERCOT’s conservation appeal started and just before it ended — also had been forced offline during the winter storm in February, according to a data analysis by the Austin American-Statesman.
  • Ten NRG generators and four Vistra generators that suffered February outages also had outages that began June 12-17, according to the Statesman.  Representatives of both companies told the newspaper that technical problems in June were not related to the problems in February and that they don’t signal larger facility problems.
  • On June 14, the 930 MW Sandy Creek Energy Station suffered a “forced extension” — meaning that the generator has not completed maintenance or technical work within the submitted timeframe and so remained offline longer than previously scheduled. In addition, several plants — including Limestone Plant Unit No. 1 and the WA Parish coal-fired plant — suffered “derates,” meaning that technical problems caused them to operate at less than full efficiency.
  • The data show more than 8,900 megawatts in unplanned outages by natural gas plants that were initiated during the five-day period, and 2,100 megawatts in unplanned coal plant outages initiated during the same period.
  • Among renewable sources, wind generators reported 4,200 megawatts of unplanned outages initiated during the five-day period, and solar units reported 2,100 megawatts of unplanned outages initiated during the period.

The new data, along with definitions of unplanned outage categories, can be found on the ERCOT website, at this link.

— R.A. Dyer