For years, the US electric power industry has witnessed a steady uptick in the total capacity of deployed energy storage resources. That growth will continue in 2019 and beyond, as the industry and regulators gain more experience with new energy storage technologies, both as stand-alone resources and complements to traditional generating units. While the large majority of energy storage capacity in the United States historically has been supplied by longer-duration (i.e., pumped storage hydroelectric) projects, grid-scale battery projects are poised to play a larger role in the energy storage market going forward.