A number of regulations aim at achieving energy and climate policy goals by mandatory increases of energy efficiency. However, in reality the resulting savings of energy can be lower than those expected that were calculated by engineers. Possible explanations for this are rebound effects, which stem from changes in patterns of behaviour. They can be divided into direct and indirect effects. The direct rebound effect shows that the demand for goods or services increases if their energy efficiency rises and they become cheaper. In contrast, indirect rebound effects imply that savings that come from higher energy-efficiency in one area allow for spending them for energy-using activities in another area. Moreover, on a macroeconomic level, the decline in demand for energy leads to lower energy prices. Ceteris paribus, the demand for energy of third parties is stimulated and thus counterbalancing savings effect. Scale, causes and impacts of rebound effects, especially in Germany, are not well researched yet and mostly unknown. REBOUND, commissioned by the German Federal Ministry of Education and Research (BMBF), aims at developing a better understanding of rebound-effects. The project pursues an interdisciplinary approach, which provides not only an economic view but also the social dimension of the rebound effect.