This report summarizes the findings from research conducted at National Renewable Energy Laboratory (NREL) to assess the technical potential for zero net energy (ZNE) building technologies and practices to reduce the impact of commercial buildings on the US energy system. In this study, NREL researchers developed quantitative predictions to answer the questions: How low can you practically go in terms of energy use? To what extent can rooftop photovoltaics supply the remaining energy needs of commercial buildings? The analysis is limited to the technical potential and does not assess market penetration or make detailed projections for how the various commercial building subsectors might evolve by 2025.