Content displaying: Capacity Factor

Battery Storage

Capacity Factor

The cost and performance of the battery systems are based on an assumption of approximately one cycle per day. Therefore, a 4-hour device has an expected capacity factor of 16.7% (4/24 = 0.167), and a 2-hour device has an expected capacity factor of 8.3% (2/24 = 0.083). Because FOM includes costs to keep the system at rated capacity, no degradation is assumed.

Round-Trip Efficiency

Round-trip efficiency is the ratio of useful energy output to useful energy input. Cole and Frazier (2020) identified 85% as a representative round-trip efficiency, and the 2020 ATB adopts this value.


The following references are specific to this page; for all references in this ATB, see References.

Cole, Wesley, & Frazier, Will A. (2020). Cost Projections for Utility-Scale Battery Storage: 2020 Update. (No. NREL/TP-6A20-75385). National Renewable Energy Laboratory.

Developed with funding from the U.S. Department of Energy’s Office of Energy Efficiency and Renewable Energy.