Evidence of an indirect rebound effect with reversible heat pumps: having air conditioning but not using it?

Regional energy efficiency programmes are of particular interest as they tackle local constraints which are not always targeted by national energy policy. Within this framework, an energy efficiency programme for existing dwellings has been implemented in a southern European region, providing financial incentives for a combination of energy efficiency actions (heat pump combined with insulation and/or solar water heater). Ex-post evaluation results of this pilot programme are reported in this study. More than 200 households were surveyed regarding their individual energy consumption as well as house and household characteristics. Likewise, the survey highlights household behaviours concerning both space heating and air conditioning, before and after refurbishment. A 3-year billing analysis is used to calculate the energy savings attributed to the operation. Evaluations are carried out taking into account critical parameters like climate differences between years or direct (enhanced space heating comfort) and indirect (use of air conditioning) rebound effects via a statistical model. Moreover, an uncertainty assessment of energy savings was realized on the basis of three scenarios (low, median and high). This study is particularly focused on the use of air conditioning by households, data rarely found in the literature, whereas the consumption linked to air conditioning should increase in the residential sector especially in southern regions. These results help in answering questions about the installation of heat pumps in existing single-family houses with respect to energy savings as well as direct and indirect rebound effects.