A summer of solar and battery storage records in Texas

Solar set a new ERCOT record (last Tuesday) on Sept. 9, generating almost half of total demand in the fast-growing Texas electricity market while providing more than 40% of the state’s electricity for seven straight hours, from 9 a.m. to 4 p.m. 

The latest record is the 17th of 2025, an astounding 7,785 megawatts (MW) higher than the first record of 22,092 MW set Jan. 24. New data from ERCOT—the Electric Reliability Council of Texas—also highlights solar’s reliability over the summer: For the period from June 1 through Aug. 31, solar met 15.2% of all demand in the ERCOT system, more than coal’s 12.5% market share.

It also covered 26.9% of peak-hour demand. The peak hour output, which averaged 20,817 MW over the course of the summer, was a 5,408MW increase from just one year ago.

The results clearly show that if you build it, solar will perform.

The same holds true for ERCOT’s dispatchable battery storage resources. There is now 15,008 MW of installed battery storage capacity across the system, which regularly charges off the grid during the early morning when solar output is high and demand low. That power is then returned to the grid in the early evening when demand is still high and solar production is waning.

Battery storage has already set four discharge records in September. The latest occurred last Thursday, Sept. 11, sending 7,741 MW, or 10.6% of total power demand back into the grid in the early evening—and preventing the need for a comparable amount of fossil fuel generation.

These records underscore solar, wind and batteries’ critical role in meeting ERCOT’s growing power demand, which has jumped 5.5% through August compared to the same period in 2024. The system’s just-released generation data through the end of August show that wind and solar supplied 90% of the increased demand, with nuclear power accounting for the remainder. In contrast, generation from the system’s coal and gas-fired resources has fallen so far this year.

Solar has been the driving force in renewables’ recent rise in ERCOT. Through August, solar generation is up 13.8 million megawatt-hours (MWh) compared to 2024 and has supplied 13.8% of total demand year to date. In a first, solar out-generated both coal and wind in August, making it the second-largest resource on the ERCOT grid, trailing only gas. Wind and nuclear generation are also up, although by smaller amounts. On the other hand, coal and gas-fired generation is down 556,838 MWh.

As a percentage of the market, wind and solar have generated 37.7% of ERCOT’s electricity needs through the first eight months of 2025, up almost 3 percentage points from a year ago. A decade ago, when solar first began growing, renewables’ market share was just 15%. Since 2016, demand in ERCOT has jumped 39.2%; renewables have provided the power for 95.7% of that growth.

The 2025 data shows that the transition away from fossil fuels in ERCOT is well under way.