A systematic review of energy efficiency home retrofit evaluation studies

This is the first systematic review of studies evaluating the energy savings and cost effectiveness of residential energy efficiency retrofit programs. We review 33 evaluations of 19 residential retrofit programs that were implemented in the United States and Europe between 1979 and 2014. Our sample is restricted to program evaluations that used actual household billing data from 159,935 retrofitted households. We report four primary findings. First, none of the studies in our sample reported deep savings (e.g., 50% or greater) from retrofit programs. The mean reduction in measured electricity and/or fuel consumption due to energy efficiency retrofits for all programs included in our sample was roughly 7.5%. However, because many households use both fuel and electricity, total household energy savings from the retrofit programs evaluated in our sample are probably smaller. Second, reported program savings decreased as the internal validity of study design increased. Third, as measured by realized savings and cost-effectiveness, the most promising retrofits were water heater insulation and programmable thermostats, whereas the least promising retrofits were storm windows and doors. Fourth, programs with high reported savings and low costs of conserved energy served low-income, fuel-heated households exclusively.