Advances in battery energy storage systems (BESS) are growing in importance with continual technological improvements and declining costs of leading battery chemistries such as lithium-ion, vanadium redox, sodium-sulfur, and others. This includes improvements with new chemistries boosting performance. BESS units play an essential role via increased integration with power supply sources with zero-greenhouse gas and zero-carbon emissions such as intermittent renewable power sources (e.g., solar PV and wind) and advances in dispatchable baseload commercial nuclear power (e.g., small modular reactors). This report discusses the viable pathways for BESS units, evaluates the status of commercially advanced battery technologies and applications, and reviews the methodologies for determining the costs and techno-economics of BESS technologies, systems, and projects. The report also provides detailed case studies along with an overview of technology types, their rated output, project status, siting and location, ownership, supply/value chain partners, cost, performance, benefits, and any other relevant data and information.