Accounting For Utility-Scale Clean Energy Storage: Background Report

Utility-scale electricity storage is expanding rapidly and becoming integral to grid operations, renewable energy integration, and corporate decarbonization strategies. It enables the time-shifting of electricity supply, enhances the value of variable renewable generation, and supports system reliability. But storage also decouples the timing of generation, consumption, and delivery; introduces conversion and auxiliary losses; and is often operated under complex dispatch regimes that existing attribute-tracking and emissions reporting frameworks do not fully address. Without clear and consistent rules, storage can undermine the integrity of clean energy claims through attribute multiplication, temporal misrepresentation, double counting, and conflation of claim types.

This background report provides a baseline overview of existing and emerging methods for accounting for renewable electricity and associated emissions when energy is stored and later discharged from utility-scale storage systems. It introduces a taxonomy of three approaches (Storage-as-Load, Storage-as-Generation, and Storage-as-Transmission), applies it to principal voluntary and compliance frameworks developed since 2015, and reviews accounting for co-located and directly connected storage. The report is a deliverable from CRS’s Clean Energy Accounting Project (CEAP) Working Group on Accounting for Utility-Scale Clean Energy Storage, and is intended as a foundation for developing consensus guidance on stored clean energy accounting.