U.S. Grid Energy Storage Factsheet
Electrical Energy Storage (EES) systems store electricity and convert it back to electrical energy when needed. 1 Batteries are one of the most common forms of electrical energy storage.
As of the end of 2022, the total nameplate power capacity of operational utility-scale battery energy storage systems (BESSs) in the United States was 8,842 MW and the total energy capacity was 11,105 MWh. Most of the BESS power capacity that was operational in 2022 was installed after 2014, and about 4,807 MW was installed in 2022 alone.
Energy storage capacity is measured in megawatt-hours (MWh) or kilowatt-hours (kWh). Duration: The length of time that a battery can be discharged at its power rating until the battery must be recharged. The three quantities are related as follows: Duration = Energy Storage Capacity / Power Rating
It can be compared to the nameplate rating of a power plant. Power capacity or rating is measured in megawatts (MW) for larger grid-scale projects and kilowatts (kw) for customer-owned installations. Energy storage capacity: The amount of energy that can be discharged by the battery before it must be recharged.
The DOE's Office of Energy Efficiency and Renewable Energy provides useful data to understand the relationship between megawatts and storage duration. Consider their example using a 240 megawatt-hour (MWh) lithium-ion battery with a maximum capacity of 60 megawatts (MW). A 60 MW system with four hours of storage could work in a number of ways:
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