Wood Mackenzie, a United Kingdom-based energy research and consultancy firm, counts 18.9 GWh of BESS installed across the US between April and June 2026, more than in any earlier quarter, from 5.4 GW of power capacity. Its latest U.S. Energy Storage Monitor, prepared with the American Clean Power Association (ACP), puts energy capacity 17% higher than a year before, while installed power slipped 7%.

That split comes down to duration. The national average duration of installed systems rose from 2.8 hours to 3.5 hours, driven by resource adequacy needs. Utility-scale projects supplied 4.7 GW / 17.6 GWh of the quarter, 8% less than a year earlier in megawatt terms as key markets become saturated. A long-duration project in California, built to meet state targets, and utility-contracted storage in Texas pushed average project duration higher, and first-half installations were still up 5%, which puts 2026 on course to match last year.

The smaller segments moved less. Residential storage installed 676 MW, its fourth largest quarter on record, 3% more than a year earlier but 15% below the first quarter, while the solar-plus-storage attachment rate reached 46%, up from 41%. The community, commercial and industrial (CCI) segment installed 48 MW, back at historical levels after California's record first quarter. Utility-scale system prices fell 2% to $916/kW.

The analysts tie the next phase to two forces. Allison Feeney, research analyst at Wood Mackenzie, said that data centre buildout strengthens the outlook in every segment, because storage can provide needed capacity faster, cheaper and more reliably than gas alone. Allison Weis, Global Head of Energy Storage at Wood Mackenzie, said that the slowdown in EV demand has become an unexpected tailwind, as manufacturers are repurposing idle EV cell capacity. John Hensley, Senior Vice President of Markets and Policy Analysis at ACP, said that storage can be deployed quickly and strengthens reliability.

Those forces shape a forecast in which annual installations grow by more than 50% in megawatt terms over five years. Utility-scale storage is expected to grow 8% a year on average as data centre demand increases, although potential trade restrictions could hold it flat in 2026 and 2027 before growth resumes in 2028 at 11% a year, as domestic cell manufacturing ramps up. CCI is projected to grow 27% between 2026 and 2031, and residential storage is expected to contract 4% this year before rebounding at 9% a year from 2027. The market would then reach 207 GW / 715 GWh installed cumulatively by 2031.

Wood Mackenzie is an energy research and consultancy firm, and it released the U.S. Energy Storage Monitor together with ACP, the US clean power trade association.