The building sector accounts for about 40% of the final energy consumption in Germany. At the same time, the sector is regarded as one of the most cost-effective options for saving CO2 emissions. To target this potential, the European Union introduced energy performance certificates (EPC). EPCs should provide clear information about the energy performance of buildings to building purchasers, owners and tenants. This study analyses, in how far EPCs have helped purchasers of owner-occupied dwellings in Germany to incorporate energy efficiency in their purchasing decisions. The results suggest that the effectiveness of EPCs is limited. Main reasons are first, that the certificates are not helpful for understanding the financial implications of energy efficiency. Second, EPCs are not viewed for most buildings due to their legal status. Third, energy efficiency is only a minor purchasing criterion for dwelling purchases. The results of the study however also point to the potential of EPCs, as these barriers can be removed. From 2013 onwards the use of the EPC will be increased due to the new EU Energy Performance of Buildings Directive (EPBD). Changes to the design of the EPC could further increase the importance of energy performance certificates and of energy efficiency. (C) 2012 Elsevier Ltd. All rights reserved.