by the numbers

Solar surpasses coal to become ERCOT’s third-largest power source in 2025

Solar represented 14 percent of energy supplied to the ERCOT electric grid in 2025. Photo via bp.com

Solar barely eclipsed coal to become the third biggest source of energy generated for the Electric Reliability Council of Texas (ERCOT) in 2025, according to new data.

In 2024, solar represented 10 percent of energy supplied to the ERCOT electric grid. Last year, that number climbed to 14 percent. During the same period, coal’s share remained at 13 percent.

From the largest to smallest share, here’s the breakdown of other ERCOT energy sources in 2025 compared with 2024:

  • Combined-cycle gas: 33 percent, down from 35 percent in 2024
  • Wind: 23 percent, down from 24 percent in 2024
  • Natural gas: 8 percent, down from 9 percent in 2024
  • Nuclear: 8 percent, unchanged from 2024
  • Other sources: 1 percent, unchanged from 2024

Combined, solar and wind accounted for 37 percent of ERCOT energy sources.

Looking ahead, solar promises to reign as the star of the ERCOT show:

  • An ERCOT report released in December 2024 said solar is on track to continue outpacing other energy sources in terms of growth of installed generating capacity, followed by battery energy storage.
  • In December, ERCOT reported that more than 11,100 megawatts of new generating capacity had been added to its grid since the previous winter. One megawatt of electricity serves about 250 homes in peak-demand periods. Battery energy storage made up 47 percent of the new capacity, with solar in second place at 40 percent.

The mix of ERCOT’s energy is critical to Texas’ growing need for electricity, as ERCOT manages about 90 percent of the electric load for the state, including the Houston metro area. Data centers, AI and population growth are driving heightened demand for electricity.

In the first nine months of 2025, Texas added a nation-leading 7.4 gigawatts of solar capacity, according to a report from data and analytics firm Wood Mackenzie and the Solar Energy Industries Association.

“Remarkable growth in Texas, Indiana, Utah and other states ... shows just how decisively the market is moving toward solar,” says Abigail Ross Hopper, president and CEO of the solar association.

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A View From HETI

Casimir’s semiconductor chips can generate power from quantum vacuum fields without the need for batteries or charging. Photo via casimir.inc

Houston-based quantum energy technology startup Casimir Inc. has been awarded an STTR Phase I contract from the U.S. Space Force's SpaceWERX to support the development of the company's solid-state generator for potential use by the Department of the Air Force.

SpaceWERX is the innovation arm of the U.S. Space Force and a division within AFWERX, the incubator and innovation arm of the United States Department of the Air Force. The Air Force Research Laboratory and SpaceWERX, along with many other government agencies, help support innovation through the Small Business Innovation Research (SBIR) and Small Business Technology Transfer (STTR) grants and contracts.

As part of the new contract, Casimir will work to refine a fully independent generator. Casimir’s solid-state power technology could support national security missions by providing reliable power even in difficult-to-service environments.

In May, Casimir emerged from stealth, netting a $12 million seed round to commercialize its quantum energy chip. The semiconductor chips can generate power from quantum vacuum fields without the need for batteries or charging. The company aims to include the chips in large-scale energy systems that can power homes, commercial infrastructure and electric vehicles.

“This STTR funds some analysis work to address our proposed scaling approach of making our chips multi-layer to increase aggregate power,” Harold “Sonny” White, founder and CEO of Casimir, tells Energy Capital.

White adds that the company will work with Texas A&M to develop chip planarization techniques to support Casimir’s plans to scale. Additionally, White says the company is working with the U.S. Space Force to explore more applications for its technology.

“Casimir’s technology brings a new capability to the market in the form of our persistent power chips,” White adds. “This approach will be relevant to ultra-low-power electronics, and with the scaling approach we are developing, connected with the STTR work, will eventually be relevant to consumer electronics and beyond.”

Casimir has previously reported that it plans to commercialize its first-generation MicroSparc chip by 2028. The chips are expected to power devices for years without the need for replacements.

The total funding for this project has not yet been disclosed.

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