Storage Futures Study: The Challenge of Defining Long-Duration Energy Storage

This report is one in a series of the National Renewable Energy Laboratory’s Storage Futures Study (SFS) Publications. The SFS is a multiyear research project that explores the role and impact of energy storage in the evolution and operation of the U.S. Power Sector. This document explores the definition of “long duration” as applied to energy storage. Given the growing use of this term, a uniform definition could aid in communication and consistency among various stakeholders. The National Renewable Energy Laboratory recommends that qualitative descriptions of long-duration energy storage always be accompanied by quantitative descriptions, and that power sector stakeholders be deliberate in how they choose to define long-duration energy storage technologies.