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Driven by the proliferation of DC energy sources and DC end-use devices (e.g., photovoltaics, battery storage, solid-state lighting, and consumer electronics), DC power distribution in buildings has recently emerged as a path to improved efficiency, resilience, and cost savings in the transitioning building sector. Despite these important benefits, there are several technological and market barriers impeding the development of DC distribution, which have kept this technology at the demonstration phase. This paper identifies specific end-use cases for which DC distribution in buildings is viable today. We evaluate their technology and market readiness, as well as their efficiency, cost, and resiliency benefits while addressing implementation barriers. The paper starts with a technology review, followed by a comprehensive market assessment, in which we analyze DC distribution field deployments and their end-use characteristics. We also conduct a survey of DC power and building professionals through on-site visits and phone interviews and summarize lessons learned and recommendations. In addition, the paper includes a novel efficiency analysis, in which we quantify energy savings from DC distribution for different end-use categories. Based on our findings, we present specific adoption pathways for DC in buildings that can be implemented today, and for each pathway we identify challenges and offer recommendations for the research and building community.

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NREL prints on paper that contains recycled content. vi This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications. through this process enabled the team to document real-world integration challenges and identify considerations that may be extended to future projects.• Created and demonstrated novel capabilities for using whole-building simulation tools to design and test control strategies for systems that integrate on-site generation, on-site storage, and flexible building loads.• Developed and explored potential methods for characterizing and synthesizing minutescale variability in building loads. These methods could be refined through future research to enable modeling of control strategies for buildings that lack 1-minute-interval metered data.Key findings from these real-world and simulation-based efforts include:• ZEB supervisory controller performance is sensitive to multiple design parameters. These can range from control choices (e.g., net load targets and battery constraints) to system characteristics (e.g., battery capacity).