​In Q3 2025, a record 2 GW of battery energy storage capacity began commercial operations in ERCOT - the market’s largest deployment of battery capacity in a single quarter.

ERCOT’s operational battery capacity has now reached 12,052 MW in rated power and 19,442 MWh in energy capacity.

In the full report, subscribers to Modo Energy's ERCOT research can learn about:

• Recent additions: What the most recent 2 GW of new battery energy storage additions suggest about future battery buildout.
• Near-term: The status of battery projects in the near-term pipeline, including where and when these are about to come online.
• Future buildout projections: How much of, and when, ERCOT’s 170+ GW queue is likely to achieve commercial operations.

​Modo Energy subscribers can download the full pipeline dataset at the bottom of the page.

​For more information on this report, reach out to the author - ovais@modoenergy.com

1. Recent Additions

21 batteries add 2 GW of new battery capacity in Q3 2025

In Q3 2025, 2,054 MW and 4,003 MWh of new battery energy storage capacity began commercial operations in ERCOT. This was ERCOT’s largest deployment in a single quarter to date, displacing Q2 2025’s record of 1,673 MW and 2,846 MWh.

21 new batteries were introduced across ERCOT’s load zones. Six of these were greater than 100 MW - the largest of which being esVolta’s Anole BESS (247MW | 480 MWh) in the North zone, Gridstor’s Evelyn BESS (220 MW | 440 MWh) in Houston, and Engie’s Cachi BESS in the South (200 MW | 400 MWh).

Engie had the most capacity commissioned in Q3, with five two-hour 50+ MW batteries achieving commercial operations, bringing 788 MW to market. This is a notable change for Engie, which has historically held a 30-strong portfolio of exclusively 1-hour-duration batteries.

Engie’s total ERCOT portfolio is now up to 2,524 MW, continuing its position as the largest battery owner in Texas, with over twice the capacity of the next owner (Enel Green Power at 1147 MW).

Battery duration continues to rise past 1.6 hours

Developers in ERCOT continue to shift towards longer-duration resources, with 18 of the 21 batteries commissioned between July and September 2025 being two hours in duration.

This brings the average duration of batteries operating in ERCOT to 1.62 hours - up from 1.5 hours at the start of 2025.

Batteries in ERCOT now rely on energy arbitrage for the majority of their revenue, giving two-hour-duration batteries an advantage.

Longer-duration storage resources are better-positioned to:

• Dispatch energy for longer during the evening net ramp - where one-hour systems regularly deplete and are unable to benefit from extended periods of peak prices.
• Engage in non-physical trading across the Day-Ahead (DA) and Real-Time (RT) markets - as more energy capacity provides a larger hedge to deliver on DA positions in case RT prices do not manifest favourably.
• Skip low-value Ancillary Service in the Day-Ahead Market to chase Real-Time Ancillary Service upside - an opportunity available once Real-Time Co-Optimization goes live in December 2025.

Extended evening price spikes are providing opportunities for prolonged energy arbitrage cycles.

Projections suggest that longer-duration storage will become the most viable investment for participants entering the market in the coming years.

To find out more, read our latest analysis on the investment case for four-hour duration storage in ERCOT.

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‘Mid-sized’ batteries see a resurgence - but continue to phase out gradually

In Q3 2025, six ‘mid-sized’ batteries with rated powers of 50-100 MW began commercial operations.

In the first half of 2025, ERCOT saw just two 10-100 MW batteries deployed - Cross Trails Storage and Dogfish BESS.

However, these new mid-sized battery deployments still fell short of the nine 100+ MW and seven <10 MW sites to come online.