The high capital cost of emerging grid storage technologies is the single largest barrier to their widespread adoption. Technology developers make bold claims about performance enhancements and economies of scale that will allow dramatic reductions in capital cost, yet costs remain prohibitively high for all technologies except in the most valuable applications. In this report we built production cost models of lithium-ion, sodium nickel chloride, and vanadium-redox flow battery systems for small- to large-scale grid storage systems to gain an understanding of the key cost components for each technology, drivers that will facilitate cost reduction, and constraints to innovative material and manufacturing approaches. Our baseline scenarios for grid-tied systems indicate that by 2022 lithium-ion batteries will reach $506/kWh, ZEBRA batteries will approach $473/kWh, and vanadium redox flow batteries will hit $783/kWh, although each chemistry will follow a different route to these cost floors. We then evaluated the ample opportunities for disruptive innovations in each chemistry’s development that may enable competitors to dramatically reduce costs and drive global market adoption.