America's Batteries Hit a Record by Lasting Longer, Not Growing Stronger

Keypoints:

• The US installed a record 18.9 gigawatt-hours (GWh) of storage in the second quarter of 2026
• Power capacity fell 7% year over year to 5.4 gigawatts
• Energy capacity still rose 16%
• Average system duration moved from 2.8 hours to 3.5 hours
• Residential energy capacity jumped 48% as home batteries got bigger

The US energy storage market installed a record 18.9 GWh in the second quarter, according to the latest US Energy Storage Monitor from Wood Mackenzie and the American Clean Power Association. The record is more surprising once you read the other number.

Installed power capacity fell 7% year over year to 5.4 gigawatts, while energy capacity rose 16%. Power measures how fast a battery can discharge. Energy measures how long it can keep going.

Longer systems explain the gap. The national average duration went from 2.8 hours to 3.5 hours. Developers are shifting to four-hour and longer batteries to meet utility adequacy requirements and local grid constraints, and data center demand adds to the push.

Homes are following the same path. The residential segment added 676 megawatts and nearly 1.2 GWh. Power capacity rose only 3%, but energy capacity jumped 48% as installers fitted larger batteries per household. The share of residential solar systems installed with batteries reached 45% in the first quarter, up from 38% a year earlier.

The grid is already showing what batteries can do. The Texas grid has scaled storage to more than 14 gigawatts, and batteries supplied a record 20% of evening electricity demand on 13 March. California's battery fleet discharged a record 12.99 gigawatts on 9 July, covering 36% of demand across the California Independent System Operator region at peak.

More is coming. The US Energy Information Administration expects 24.3 gigawatts of new battery storage in 2026, up from the 15 gigawatt record set in 2025. Google and the utility Xcel Energy plan a 300 megawatt, 30 GWh battery project, which they describe as the largest announced anywhere by energy capacity. That works out to about 100 hours of duration.

John Hensley of the American Clean Power Association says storage can be deployed quickly, strengthens reliability, and helps the grid make better use of both existing and new generation. If duration keeps stretching, will the next record be measured in hours rather than gigawatts?