To realize the immense opportunity for energy savings from retrofitting existing residential buildings, and to develop a self-sustaining energy efficiency marketplace, accurate data about energy efficiency opportunities needs to be made available at a large scale to all market actors and decision makers. But identifying cost-effective energy efficiency measures for individual homes, or for groups of homes, can be a formidable and expensive task. Energy efficiency programs have traditionally relied on detailed on-site energy audits, building energy modeling, and data analytics, but that approach cannot be scaled quickly and effectively. Alternatively, crude assumptions can be made based on home age and location for targeting, but that does not provide sufficient analytical rigor. We propose a hybrid solution which addresses the limitations, and draws on the strengths, of each approach. Building upon recent advances in data science, machine learning and cloud computing with EnergyPlus⢠and OpenStudio®, and combining them with automated data acquisition of non-traditional sources, we propose to build a new targeting tool called XeroHomeâ . XeroHomeâ will be a building energy modeling and data analytics-based tool designed to generate energy efficiency recommendations for homes quickly, accurately, and at scale. XeroHomeâ will provide a platform to provide un-biased energy upgrade recommendations for homeowners, and a channel for finding and engaging with potential program participants and customers for energy efficiency programs, and technology & service vendors in the home performance industry. Under Phase 1 Vistar Energy will develop a fully-functioning pilot-scale prototype of the XeroHomeâ tool. Working with one of our partner utilities, we will identify 100-500 test homes and use the XeroHomeâ prototype to identify energy upgrade op