Winter Storm Elliott spread extremely cold temperatures across much of the country and knocked out power for millions just before Christmas. Utilities and grid operators prepared for the storm as it was coming down the pike, but they still underestimated the energy demand it would trigger, as well as the number of outages at fossil fuel power plants—mainly natural gas-fired, plus some coal-fired plants.
In Elliott’s aftermath, the National Oceanic and Atmospheric Administration aptly called the storm a “historic arctic outbreak.” While the event was indeed historic, the types of failures in the US fossil-heavy power system that occurred during the storm weren’t new. And although policymakers and the utility industry have learned lessons from previous cold weather events, there was an unfortunate amount of similarities between Elliott and those events, demonstrating that much still needs to be done to strengthen the US power system.
I will go over some aspects of Winter Storm Elliott that illustrate what we know so far, since there is still a lot of information yet to be publicly released. Then I’ll go back to some past events to show that we’ve been in similar situations before—and that there’s more we can do to lower the risk that they will happen again.
The scale of Elliott’s outages and plant failures
The number of US ratepayers who were in the dark at the same time during Elliott peaked at 1.6 million, and a total of 6.35 million customers experienced outages at some point during the storm. The amount of publicly available details about what happened differs by location.
North Carolina and Tennessee experienced the most customer outages, but Duke Energy and the Tennessee Valley Authority—the main power providers for those respective states—have apparently provided only limited information about what happened thus far. In a presentation to North Carolina regulators, Duke named several specific resources it lost during the storm—all fossil fuel generators—but didn’t provide a detailed breakdown of what types of failures prompted it to begin rolling blackouts on Christmas Eve.
Erie County, New York—home to Buffalo—was devastated by a lake-effect storm that killed at least 46 people and left thousands without power for days. Buffalo’s main utility, National Grid, told the local news media that some of its substations froze during the storm, but similarly doesn’t appear to have released any detailed reports on what the company knows so far.
Other power sector players have been more forthcoming based on the preliminary information they have.
PJM Interconnection: The country’s largest grid operator, PJM Interconnection, which covers all or some of 13 states plus Washington, D.C., experienced widespread power plant outages during the storm, the vast majority of which were due to equipment issues at gas-fired power plants. When these unplanned plant outages peaked on the morning of December 24, gas plants made up about 46 percent of the capacity that should have been available but more than 70 percent of the plant outages. In total, nearly 40 percent of the operator’s gas fleet was offline during this time.
Coal plants, meanwhile, made up about 24 percent of the capacity that should have been available and 16 percent of the plant outages. Nearly 17 percent of the coal fleet was offline at the time.
In addition to equipment issues, fuel supply was another significant contributor to plant outages, as Appalachian region gas well production plunged nearly 30 percent. Gas pipeline operators notified PJM of various issues in their systems that constrained the transport of gas to power plants, including frozen production wells and outages at compressor stations, which normally keep the gas moving within the pipelines.
PJM had to urge households within its footprint to conserve energy, and luckily, those households didn’t experience widespread outages despite all the power plant failures. The operator nevertheless appropriately described the underperformance as “unacceptable,” and has preliminarily estimated it will levy $1 billion to $2 billion in penalties against power plant owners.
The Midcontinent Independent System Operator (MISO): A large grid operator in the middle of the country, MISO, also reported that it didn’t suffer customer outages, but it very easily could have not been the case given the performance of the fossil-fueled power fleet. During the storm, MISO experienced a troubling amount of power plant outages, which reached 50,000 megawatts (MW) on Christmas Eve. That’s equivalent to more than a third of the capacity that should have been available.
Of the 50,000 MW in unplanned plant outages, gas made up 44 percent and coal made up another 32 percent. During this time, about 40 percent of the coal fleet and 40 percent of the gas fleet was offline. While MISO said that the availability of gas supply contributed to these unplanned outages, it hasn’t yet provided a breakdown of how many of the outages were due to fuel supply, plant equipment, or other factors in the same way PJM did.
The Electric Reliability Council of Texas (ERCOT): Unlike PJM and MISO, ERCOT—which is the grid operator for most of the Lone Star State—hasn’t yet published any preliminary reports on Winter Storm Elliott. ERCOT does, however, routinely publish snapshots of unplanned plant outages in its region at any given time. These data suggest that, once again, gas was the largest contributor to plant outages during the storm.
I say “suggest” because there are some issues with the data ERCOT publishes, including the fact that the most common reported reason for gas plant outages was “Other,” which doesn’t explain anything at all about the nature of the outage. Aside from that category, fuel supply was the most common reason that ERCOT reported for unplanned gas plant outages.
Historic, but more of the same
While Winter Storm Elliott was a historic weather event, this type of underperformance by the fossil-fuel power fleet during cold snaps is nothing new.
In February 2021, for example, Winter Storm Uri plunged the central part of the country into extremely cold temperatures that caused more than 1,000 generating units to go offline or operate at reduced capacity, the majority of which were gas-fired units. The Federal Energy Regulatory Commission noted in a post-storm report that this was the fourth cold-weather event in the past 10 years alone that jeopardized the reliability of the US power grid.
Uri’s impact was the most devastating in Texas, which experienced widespread multiday customer outages and the deaths of 246 people, nearly two-thirds of which were caused by hypothermia. A slew of factors was at play, but notably, the grid in Texas is uniquely isolated from the rest of the country, with very few transmission lines that can import electricity from neighboring states. Still, the largest factor—the failure of the state’s gas infrastructure—was similar to what happened during Elliott: cold weather-related challenges with gas production, transportation, and burn at power plants.
Going back a few more years, a polar vortex in January 2014 put much of the eastern half of the country into extreme cold, dropping temperatures 20 to 35 degrees Fahrenheit below average. To name a severe example, the wind chill temperature fell to -63 degrees F in Grand Marais, Minnesota.
The resulting power outages weren’t nearly as severe in magnitude or length as those during Uri, but the fossil-fuel power plants in the area still experienced significant failures. Gas-fired plants accounted for more than 55 percent of the plant outages during the event, while coal plants accounted for 26 percent, according to a 2014 report by the nonprofit North American Electric Reliability Corporation (NERC), which sets reliability standards for North American power grids.
In that report, NERC said that the lessons learned during the 2014 Polar Vortex validated concerns it had raised less than a year earlier about the electric power sector’s rapidly growing dependence on gas. Instead of heeding those lessons, US utilities since 2014 have only increased their reliance on gas, which surpassed coal in 2016 as the leading fuel source for power generation. As extreme weather events become more common due to climate change, the United States is going to have to strengthen the reliability and resilience of its power grid to prevent the type of devastation we’ve seen in recent years, Elliott being just the most recent example.
Where do we go from here?
There are signs that the country is moving forward with the investments necessary to increase grid reliability while simultaneously addressing climate change. The 2021 Infrastructure Investment and Jobs Act provides nearly $15 billion in federal funding for grid improvements, which includes energy storage as an option. The 2022 Inflation Reduction Act (IRA), which will invest $369 billion in climate and energy solutions, adds more flexibility to energy storage tax credits, as well as new tax credits for clean hydrogen, which can potentially be used as a long-duration storage technology. (See my colleague Julie McNamara’s blog for caveats about hydrogen.)
The IRA will also speed investments in wind and solar projects, which are limited by weather conditions but will be used to charge the various energy storage systems that will be integrated with the grid, so that clean electricity will be available when the country needs it most. Further, while wind turbines also experienced some freezing issues during recent cold weather events, solar, wind and battery storage have benefited grid reliability during extreme weather events in recent years—both hot and cold—that will become more common because of climate change.
To cite some examples, MISO said that during Winter Storm Elliott, wind production remained high, which supported the transmission system and helped make up for the shortfalls caused by outages at fossil-fuel plants. In PJM, wind resources delivered more than three-and-a-half times what they had committed to provide. And during a California heatwave in the summer of 2022, battery storage resources installed in recent years helped keep the lights on by using abundant solar power to charge up.
To reduce the risk of grid failures and prevent more Elliott- and Uri-type events, the United States must diversify its power system and reduce its reliance on fossil fuels, namely gas and coal. The country can achieve this and mitigate climate change-induced extreme weather by transitioning to cleaner, more flexible, and more resilient resources such as those incentivized by the IRA. The Union of Concerned Scientists and its allies are pushing vigorously to make sure this transition continues expeditiously.