This edition of the Handbook is a how-to guide for electric systems engineers/planners, energy storage system vendors, and investors to aid in the selection, procurement, installation, and/or operation of stationary energy storage systems in today’s electric grid. Various perspectives of grid electricity storage are presented for different stakeholders: generators and system operators, load-serving entities (LSEs) with various ownership structures, and customers. The Handbook includes a review of the current status of technical, financial, regulatory, and ownership issues that impact energy storage adoption, primarily with a U.S.-centric focus. Much of the material presented in this edition of the Handbook has been condensed and updated from existing reports from Sandia National Laboratories (SNL), EPRI, National Rural Electric Cooperative Association (NRECA), other national laboratories, and industry sources published from the mid-1980s to the present. This edition presents updated information on storage technologies and their benefits in an operational and regulatory environment and recognizes energy storage as a grid component in further detail than the 2003 Handbook.