major milestone

Houston geothermal startup selects Texas location for first energy storage facility

Houston startup Sage Geosystems has tapped a utility provider for an energy storage facility in the San Antonio metro area. Photo via sagegeosystems.com

Houston-based geothermal energy startup Sage Geosystems has teamed up with a utility provider for an energy storage facility in the San Antonio metro area.

The three-megawatt EarthStore facility will be on land controlled by the San Miguel Electric Cooperative, which produces electricity for customers in 47 South Texas counties. The facility will be located in the town of Christine, near the cooperative’s coal-fired power plant.

Sage says its energy storage system will be paired with solar energy to supply power for the grid operated by the Electric Reliability Council of Texas (ERCOT). The facility is set to open later this year.

“Once operational, our EarthStore facility in Christine will be the first geothermal energy storage system to store potential energy deep in the earth and supply electrons to a power grid,” Cindy Taff, CEO of Sage Geosystems, says in a news release.

The facility is being designed to store geothermal energy during six- to 10-hour periods.

“Long-duration energy storage is crucial for the ERCOT utility grid, especially with the increasing integration of intermittent wind and solar power generation,” says Craig Courter, CEO of the San Miguel Electric Cooperative.

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A View From HETI

A new report from the U.S. Energy Information Administration shows that wind and solar supplied more than 30 percent of ERCOT’s electricity in the first nine months of 2025. Photo via Unsplash.

Since 2023, wind and solar power have been the fastest-growing sources of electricity for the Electric Reliability Council of Texas (ERCOT) and increasingly are meeting stepped-up demand, according to a new report from the U.S. Energy Information Administration (EIA).

The report says utility-scale solar generated 50 percent more electricity for ERCOT in the first nine months this year compared with the same period in 2024. Meanwhile, electricity generated by wind power rose 4 percent in the first nine months of this year versus the same period in 2024.

Together, wind and solar supplied 36 percent of ERCOT’s electricity in the first nine months of 2025.

Heavier reliance on wind and solar power comes amid greater demand for ERCOT electricity. In the first nine months of 2025, ERCOT recorded the fastest growth in electricity demand (5 percent) among U.S. power grids compared with the same period last year, according to the report.

“ERCOT’s electricity demand is forecast to grow faster than that of any other grid operator in the United States through at least 2026,” the report says.

EIA forecasts demand for ERCOT electricity will climb 14 percent in the first nine months of 2026 compared with the same period this year. This anticipated jump coincides with a number of large data centers and cryptocurrency mining facilities coming online next year.

The ERCOT grid covers about 90 percent of Texas’ electrical load.

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