December 08, 2021

Making the Grid More Climate-Resilient: Report on February 2021 Cold Weather Outages in Texas and South Central US Highlights the Challenges


The November 16, 2021, “February 2021 Cold Weather Outages in Texas and the South Central United States” report1 (Report) by staff of the Federal Energy Regulatory Commission (FERC), the North American Electric Reliability Corporation (NERC) and certain NERC-recognized regional entities2 (Regional Entities) describes the severe cold weather event (Event) occurring between February 8 and 20, 2021, and how it impacted the reliability of the bulk electric system (BES or grid) in Texas and the South Central United States.

During the Event, extreme cold temperatures and freezing precipitation led 1,045 individual BES generating units (with a combined 192,818 MW of nameplate capacity) in Texas and the South Central United States to experience 4,124 outages, derates or failures to start. Each affected individual generating unit could, and in many cases did, have multiple outages from the same or different causes.

For perspective on how significant the generating unit outages during the Event were, including generation already on planned or unplanned outages, the Electric Reliability Council of Texas (ERCOT) averaged 34,000 MW of generation being unavailable (based on expected capacity) for over two consecutive days, from 7:00 a.m. February 15 to 1:00 p.m. February 17, equivalent to nearly half of ERCOT’s all-time winter peak electric load of 69,871 MW.

The Event was the fourth cold weather-related event in the past 10 years to jeopardize BES reliability and, with a combined 23,418 MW of manual firm load shed, the largest controlled firm load shed event in US history. In each of the four BES events, planned and unplanned generating unit outages caused energy emergencies and in 2011,3 2014 and 2021 triggered the need to shed firm BES load. The unplanned generation outages that escalated during the Event were more than four times as large as the previous largest event.

Key findings in the Report include (emphasis added):

  • From February 8 through 20, in the Event area, a total of 1,045 individual generating units—58 percent natural gas-fired, 27 percent wind, 6 percent coal, 2 percent solar, 7 percent other fuels, and less than 1 percent nuclear—experienced 4,124 outages, derates or failures to start. Of those outages, derates and failures to start, 75 percent were caused by either freezing issues (44.2 percent) or fuel issues (31.4 percent).
  • Natural gas fuel supply issues caused the majority, 87 percent, of the 31.4 percent of outages and derates due to fuel issues and caused 27.3 percent of all outages, derates and failures to start during the Event.
  • In addition to the 44.2 percent of outages and derates caused by freezing issues, the 21 percent caused by “mechanical/electrical issues” also indicated a relationship with the cold temperatures—as temperatures decreased, the number of generating units outaged or derated due to mechanical/electrical issues increased.
  • Despite multiple prior recommendations by FERC and NERC, as well as annual reminders in various Regional Entity workshops, that generating units take actions to prepare for the winter (and detailed suggestions provided for winterization), 49 generating units in SPP (15 percent or 1,944 MW of nameplate capacity), 26 units in ERCOT (7 percent or 3,675 MW), and 3 units in MISO South (4 percent or 854 MW) still had no winterization plans, and 81 percent of the freeze-related generating unit outages occurred at temperatures above the unit’s stated ambient design temperature. Generating units that experienced freeze-related outages above the unit’s stated ambient design temperature represented about 63,000 MW of nameplate capacity.

The Report’s recommendations include proposed revisions to mandatory electric reliability standards (Reliability Standards) and policy actions to weatherize natural gas production and distribution.

The proposed revisions of Reliability Standards made by the Report would require:

  • Generator Owners (GOs) to identify and protect cold-weather-critical components;
  • GOs to retrofit existing generating units to, and require new generating units being built to, operate to specific ambient temperatures and weather based on extreme temperature and weather data and account for effects of precipitation and cooling effect of wind;
  • GOs or Generator Operators (GOPs) to perform annual training on winterization plans;
  • GOs that experience freeze-related outages to develop Corrective Action Plans;
  • GOs or GOPs to provide the applicable balancing authority (BA) with the percentage of the total generating unit capacity that the BA can rely on during the “local forecasted cold weather”; and
  • GOs to account for effects of precipitation and the accelerated cooling effect of wind when providing temperature data to BAs.

However, the Report also recommends that: GOs have the opportunity to be compensated for the costs of retrofitting their generating units to perform at specified ambient temperatures (or designing any new units to do so); FERC, NERC and the Regional Entities host a joint technical conference to discuss how to improve the winter readiness of generating units before the recently approved Reliability Standards revisions become effective; and GOs’/GOPs’ freeze protection plans include certain times for inspection and maintenance (e.g., before and after winter and before specific cold weather events).

Regarding natural gas fuel supplies (the second most frequent cause of unplanned outages and derates), the Report recommends that Congress, state legislatures and regulatory agencies with jurisdiction over natural gas infrastructure facilities require those facilities to implement and maintain cold weather preparedness plans; that natural gas infrastructure facilities undertake voluntary measures to prepare for cold weather; and that GOs/GOPs identify the reliability risks related to their natural gas fuel contracts so that they can provide the BAs with the percentage of total generating unit capacity that the BA can rely on during the “local forecasted cold weather”; and, to address the recurring challenges stemming from natural gas-electric infrastructure interdependency, that FERC consider establishing a forum to identify concrete actions to improve the reliability of the natural gas infrastructure system necessary to support the BES.

Following the Event, Texas passed Senate Bill 3 (SB3) and, as required thereunder, the Public Utility Commission of Texas (PUCT) has adopted4 the required regulations to weatherize electric generation in ERCOT, and the Texas Railroad Commission (RRC) adopted5 new regulations regarding the Critical Designation of Natural Gas Infrastructure and customers.

It is clearly too early to tell if these new requirements will be effective in preventing the impacts of other extreme weather events like the Event, and, of course, other regulators may need to take similar action for the BES to avoid similar events in the future.



1 The Report assumes familiarity with electric transmission system and generating unit operations but includes linked materials for other readers. The Report and related FERC releases can be viewed here.

2 Namely, the Midwest Reliability Organization, Northeast Power Coordinating Council, ReliabilityFirst Corporation, SERC Corporation, Texas Reliability Entity and Western Electricity Coordinating Council.

3 For which a joint FERC/NERC report was also prepared and is available here.

4 The PUCT adopted final regulations, new 16 Texas Administrative Code (TAC) §25.55, on October 21, 2021; see here.

5 The RRC adopted a new regulation, 16 TAC §3.65, on November 30, 2021; see here.

Stay Up To Date With Our Insights

See how we use a multidisciplinary, integrated approach to meet our clients' needs.