Utilities, regulators, and private industry have begun exploring how battery-based energy storage can provide value to the U.S. electricity grid at scale. However, exactly where energy storage is deployed on the electricity system can have an immense impact on the value created by the technology. With this report, we explore four key questions: What services can batteries provide to the electricity grid? Where on the grid can batteries deliver each service? How much value can batteries generate when they are highly utilized and multiple services are stacked? What barriers—especially regulatory—currently prevent single energy-storage systems or aggregated fleets of systems from providing multiple, stacked services to the electricity grid, and what are the implications for major stakeholder groups?