This second report in the Storage Futures Study series provides a broad view of energy storage technologies and inputs for forthcoming reports that will feature scenario analysis. This report also presents a synthesis of current cost and performance characteristics of energy storage technologies for storage durations ranging from minutes to months and includes mechanical, thermal, and electrochemical storage technologies for the electricity sector. The analysis covers a broad range of storage technologies that are currently receiving significant attention from the investment community, as well as in the media. In addition, for a smaller set of technologies—primarily lithium-ion batteries—this report provides current and a range of future cost trends until 2050, which is intended for scenario analysis at both the bulk power and distribution system scales.