Solar Power Makes Texas-Size Surge

Over the past decade, solar capacity in ERCOT’s service area has expanded from 15 megawatts to 2,281 megawatts.
Visual created with images via Pixabay

Texas’ power generation market is rapidly reshaping, and solar is having a big impact. According to a new report issued by the Institute for Energy Economics and Financial Analysis, new utility-scale solar is poised to push much of the remaining coal-fired power fleet across the Lone Star State into retirement over the next few years.

The report—Solar Surge Set to Drive Much of Remaining Texas Coal-Fired Fleet Offline—shows an increasing vulnerability of coal plants across the Electric Reliability Council of Texas’ managed market, which comprises most of the state. Specifically, the report’s authors point out to roughly 70 percent of daytime coal-fired generation in ERCOT being at risk by 2022.

Solar herald

In the past 10 years, solar power capacity has increased in the U.S. by almost 4,000 percent; in Texas, across ERCOT’s area, the installed solar capacity grew from 15 megawatts in 2010 to 2,281 MW at the end of 2019, representing a 15,107 percent increase. Moreover, by the end of 2020, ERCOT’s installed solar capacity is projected to surpass 5,800 MW. Meanwhile, in the area served by ERCOT, there are 11 remaining coal-fired generators.

While solar is still a tiny fraction of ERCOT’s overall generation, the sustained progress is promising. Last year, solar supplied 1 percent of ERCOT’s overall generation, and in June this year, solar generation supplied 4 percent to 5 percent of daytime electricity demand on many occasions. Considering its low cost and the state’s grid—which pays for electricity produced rather than generation capacity—solar is gulping down market share.

Despite the pandemic and the oil price collapse at the start of the year, power demand increased slightly compared to last year. Yet, in the first half of 2020, coal-fired generation has fallen across ERCOT by more than 8.6 million megawatt-hours, while solar and wind generation has increased by almost 21 percent to more than 8.5 million MWh.


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By the end of May 2020, 420 MWs of solar power came online in the area and another 1,057 MW were synchronized with the grid, in preparation for full deployment, bringing ERCOT’s total installed capacity to 3,748 MW. Another 2,053 MW are anticipated to come online by early 2021—at the latest—having already secured interconnection agreements and project-specific financing needed for the transmission service provider.

The study’s analysts calculated the expected generation from the projected capacity that is currently being built in ERCOT and slated to come online by the start of 2022. Their findings show two takeaways:

By January 2022, daily solar generation in the ERCOT area will likely surpass 80,000 MWh during the long summer days, which would put as much as 70 percent of its daytime coal-fired generation at risk. The second conclusion is that, according to the data, solar poses a similar daytime threat to coal even during the short-daylight winter months. In comparing the generation for the month of January 2020 with the expected solar generation beginning in January 2022, the analysts discovered that solar could put 70 percent of coal’s daytime generation at risk in just two years’ time.

Battery storage gains momentum

While solar is strengthening its presence in ERCOT’s market share, battery storage technology is turning from a peripheral into a must-have component for utility-scale solar projects in and around Texas. Examples abound.

NextEra’s contract with Western Farmers Electric Cooperative to develop a 700-MW wind-solar-battery project with 200 MW of storage; New Mexico’s Public Service Co. of New  Mexico is replacing its 560-MW stake in the 874 MW San Juan Generating Station with a larger mix of new generation sources that regulatory staff believe should include 650 MW of solar and 300 MW of battery storage. The Gemini Solar Project, touted as the biggest solar farm in the country, will include a 380-MW solar-powered battery system tied to a 690-MW array of collector panels.

The ERCOT area registered substantial increases in wind capacity, too. The installed wind capacity in the area totaled nearly 24,000 MW at the end of 2019, an almost 15,000-MW expansion throughout the decade, which boosted wind’s share of the ERCOT power generation market from 6.2 percent to 19.7 percent, nearly on par with the 20.3 percent share from the state’s coal generators.

Cooling coal

Image via Pixabay

It’s been three years since the last round of coal plant retirements in Texas. Vistra Energy closed 2,408 MW of capacity—Sandow units 4 and 5, and Big Brown units 1 and 2. A combination of low wholesale power prices with an oversupplied renewable generation market and low natural gas prices led to Vistra’s decision to cease operations at the Sandow and Big Brown plants.

This year, a new retirement is planned—Oklaunion, a single-unit, 650-MW coal plant operating since 1986 will be retired in October. Operated by American Electric Power, it is located near the Texas-Oklahoma border and its output is split between ERCOT (73 percent) and the Southwest Power Pool (27 percent).


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Of the 10 remaining coal plants, six came online between the 1970s and 1990s and their capacity factor has dropped considerably in recent years. Their carbon dioxide emissions, on the other hand, has remained high, with some ranking among the largest emitters in the country.