Rapid change is underway in the energy storage sector. Prices for energy storage systems (ESSs) remain on a downward trajectory. The deployment of ESSs (measured by capacity or energy) continues to grow in the U.S., with a widening array of stationary power applications being successfully targeted. This study evaluates the current state of technology, market applications, and costs for the stationary energy storage sector. It emphasizes the importance of understanding the full lifecycle cost of an energy storage project, and provides estimates for turnkey installed costs, maintenance costs, and battery decommissioning costs. The report also provides a view as to how technologies and costs will evolve in the future. Focus is placed on lithium ion and flow battery technologies; the former being the current market leader, with the latter in the early stages of market adoption. Results of this analysis support the continued evaluation and potential deployment of energy storage as a grid asset.