This deliverable provides a high-level review of key energy storage technologies being worked on across EPRI, including various batteries, mechanical and thermal energy storage types. Focus is on technology for which EPRI has been able to independently verify data. Summaries are given on key issues that characterize energy storage technologies: costs and performance (including round-trip efficiency [RTE]); flexibility and grid services; and technology maturity including technology readiness level (TRL). The information provided in this deliverable can be used as an easy-to-access summary of energy storage types and a high-level comparison of their attributes. References are provided to obtain more detailed information.