Retrofit experience in U.S. multifamily buildings: Energy savings, costs, and economics

We present the energy savings and costs of conservation measures in U.S. multifamily buildings based on an analysis of measured data from our data base of over 25,000 dwelling units. Median energy savings were 1450 kWh/unit in electric-heat buildings and 14 MBtu/unit in fuel-heat buildings, or ~14–16% of pre-retrofit consumption. We found that differences in pre-retrofit usage, size of investment, and choice of retrofit strategy were particularly influential in explaining the variation in energy savings among buildings. Retrofit costs were typically much lower in fuel-heat buildings than in electric-heat buildings ($370/unit vs $1600/unit). Median payback time in fuel-heat buildings was 6 yr; paybacks were typically 20–25 yr in electric-heat buildings where the emphasis was on costlier shell improvements. Comparisons of pre-retrofit predictions with actual savings showed fairly good agreement on average, in five out of seven programs, although the variance for individual buildings was often quite large. Extrapolating these measured retrofit results to the U.S. multifamily stock suggests opportunities for saving 0.2–0.5 quads/yr (resource energy), which represents 10–22% of current consumption.