What failed in Texas?

By comparison to others, the power grid in Texas has uniquely and grandly failed during this winter storm. Other systems with similarly anomalous weather did not endanger their customers, but this was the second time in ten years that the Texas system has failed.

In some ways Texas’ power grid is unique, and in some ways it is conventional. Like all electrical grids, demand fluctuates daily, weekly and seasonally, and it has more nameplate generating capacity than it needs at any one point in time. Unlike others, Texas’s system is partitioned and deregulated. The now well-known Electric Reliability Council of Texas does not generate electricity; it buys it from private generating companies who bid to deliver electricity over short time periods. 

In 2020, ERCOT bought 23% of its electricity from wind generators, a number which has been steadily increasing from 9% in 2011. ERCOT has for many years worked around the intermittency of wind generators. In its planning for the winter as a whole, ERCOT expected to rely on 67 GW of electricity from thermal sources – gas, coal and nuclear in that order – and it planned for only 6 GW of electricity from wind turbines on average. In the three days before the outages began, wind generation averaged 5.7 GW while thermal sources averaged 53.1 GW. 

As power demand spiked over 70 GW, widespread generation problems developed, and blackouts began. Wind power initially delivered about 1 GW below what had been contracted, but then it supplied slightly more than contracted during the next day. By contrast, ERCOT itself as well as outside experts have identified natural gas generation as the key failure. 

ERCOT’s senior director of operations identified the primary cause as the failure of gas production, delivery and generation. He offered, “It appears that a lot of the generation that has gone offline today has been primarily due to issues on the natural gas system.”

Ed Crooks of energy analytics firm Wood MacKenzie opined, “The crisis in Texas was not caused by the state’s renewable energy industry. The largest loss of generation came from gas-fired power plants, with the drop-off from wind farms a long way behind.” More colorfully, a professor at the University of Texas at Austin summarized, “Gas is failing in the most spectacular fashion right now.”

This graph from the EIA shows how natural gas was called upon and successfully stepped up to met the demand as the winter weather settled in. It also shows how all sources stumbled as the worst of the weather arrived very early on Monday morning. 

Over the next two days, the cold held generation from all fuel sources to levels lower than the days before. Wind generation slid 2.3 GW from the recent benchmark, but the cold took 2.9 GW of coal offline, 1.4 GW of nuclear offline and 6.9 GW of natural gas generation offline. These outages continue to today.

Other generating sources were similarly impacted and could not step in to fill the gap between the increased demand and decreased generation. In total on Tuesday, 30 GW of natural gas, coal and nuclear could not be brought online while 16 GW of wind capacity was unavailable. As mentioned before, ERCOT had only planned for wind to contribute an average of 6 GW during the winter with wide variation from week to week, and wind was still contributing 3.4 GW to the grid. By contrast, ERCOT had planned for 67 GW from thermal sources and could not access 30 GW of it. 

The deep shortage caused a stratospheric spike in the wholesale price of electricity. Instead of getting around $25 per megawatt as they normally do, generating sources could suddenly get up to $9,000 for their product (the maximum allowed). It had been planned mainly to leave the wind power offline, but that bonanza price created by the failure of the system as a whole prompted the Herculean efforts to thaw out wind turbines. Similarly if the turbines had been equipped with de-icing technology as they are in colder climes (even as far north as the Arctic Circle), then the extraordinary steps would also not have been necessary. 

Other states that saw similarly anomalous weather and that also rely on a mix of sources did not see the kind of epic failure experienced in Texas. Circumstances suggest, and experts have opined, that those other systems were merely better prepared for the cold. 

The last time ERCOT left 3 million Texans without power was almost exactly ten years ago, for a couple of days in early February 2011. An investigation by the federal energy regulatory agencies found that the cause was inadequate winterizing and insufficient fuel reserves. 

The investigations into the 2021 failure seem likely to find the same systematic problem, but they almost certainly won’t lay the blame on unexpected failures of wind turbines. The real question will be why the generators in Texas systematically failed to spend the money to winterize their plants and to secure their supplies so that they could provide heat for their customers when they most need it.

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Please contribute to the conversation in the comments. For your reference, these are the best resources (and the chief sources) used in the analysis above: EIA's Hourly Grid Monitor, on-going coverage by the Texas Tribune, the previous investigation by FERC, and a helpful explanation from a columnist at the Houston Chronicle.