Residential energy efficiency improvements often have a smaller effect than expected. Although there is agreement on the existence of this effect, called the rebound effect, there is no agreement on the size of the effect. The objective of this study was to investigate the potential of using serious games to assess this effect. We used a game in which participants play home owners who manage their households in terms of energy consumption. Results of experiments with 50 players showed signs of the rebound effect when players with a low efficiency house reduced their energy consumption more than players with a high efficiency house. In addition, some issues related to previous studies were addressed, such as the possibility to perform an ex-ante assessment and to conduct the study in a controlled environment. Calculations of the size of the rebound effect depended on the approach used to determine the expected effect and showed differences between appliances.