This study conducted a benefit-cost impact evaluation of the research and development activities of the Building Technologies Office on investments in heating, ventilation, and air conditioning (HVAC), water heating, and appliance technologies. The analysis suggests that BTO investments in this R&D has generated an estimated benefit-to-cost ratio between 20-to-1 and 66-to-1 with an internal rate of return between 38% and 51%. This report is a retrospective look at investments made from 1976 through 2015.