The United States continued a trend of significant growth in large-scale battery storage capacity in 2020, when year-end U.S. battery power capacity reached 1,650 megawatts (MW). According to our report, Battery Storage in the United States: An Update on Market Trends, U.S. battery power capacity grew by 35% in 2020 and has tripled in the last five years. The trend is expected to continue; utilities have reported plans to install over 10,000 MW of additional large-scale battery power capacity in the United States from 2021 to 2023—10 times the capacity in 2019.

Much of the recent increase in new storage capacity comes from battery energy systems co-located with or connected to solar projects.

Five states account for more than 70% of U.S. battery storage power capacity as of December 2020. California has the largest share at 31% (506 MW) of the U.S. total. Texas, Illinois, Massachusetts, and Hawaii each have more than 50 MW of power capacity.

Small-scale battery storage also continues to grow; in 2019, the United States had more than 400 MW of total small-scale battery storage power capacity. California accounts for 83% of this capacity. Small-scale batteries have a nameplate power capacity of 1 MW or less.

The terms power capacity and energy capacity describe different energy measurements. Energy capacity is the total amount of energy the battery system can store. Power capacity is the maximum amount of power the battery can discharge at a given moment. Battery storage systems are usually designed to maximize either their power or energy capacity, depending on the battery’s intended use.

Large-scale U.S. battery system energy capacity also continued to increase, reaching 1,688 megawatthours at the end of 2019, a 30% increase from 2018.

Additional information on the battery storage industry, including regional and ownership trends, chemistries, applications, costs, and future project developments, is available in our recently updated report, Battery Storage in the United States: An Update on Market Trends.