Battery storage capacity more than tripled in the US last year as the way utility-scale energy storage systems and their use cases evolved to meet changing grid operator demands.
Last year, more energy storage systems (ESS) were used as an arbitrage resource to flatten renewable power generation curves alongside traditional services.
Installed capacity rose from 1.4GW in 2020 to 4.6GW last year, according to the early release of the 2021 EIA-860 data from the U.S Energy Information Administration (EIA)
The increase was driven by the addition of 106 utility-scale batteries with 3,202MW of capacity coming into commercial operation.
Around 78% of the battery storage capacity added in 2021 was built in regional transmission organisation (RTOs) service territories, which is consistent with historical averages.
The rise was also believed to have happened because of more applications, or use cases, beyond the traditional ancillary services that have been predominant since 2016.
While ancillary services— particularly frequency response and ramping or spinning reserve— continue to represent a significant share of the use case capacity, ESSs are now also being used for arbitrage, load management, and response services to excess renewables generation.
In 2021, arbitrage use was cited for more than half of the capacity installed. That represented more than 2.7GW of battery capacity— including 83% (1,887MW) of the battery capacity added in the California Independent System Operator (CAISO) service territory.
Load management also saw a significant increase in battery storage capacity with a 744MW increase in capacity last year, rising from 110MW in 2020 to 854MW in 2021.
More than 93% of the battery capacity that went online in 2021 was co-located with solar; this use case gained 1,086MW of capacity in 2021 and was “reflective of the continued industry-wide growth of paired renewable and storage capacity”, according to EIA.