The success of energy certification in European Union (imposed by the Energy Performance of Buildings Directive) depends to a large extent on the conditions in Member States. Energy consumption in residential buildings varies greatly depending on the type of building, construction year and many country-specific factors, such as climate. The countries have very different energy savings potentials depending on the size and condition of the housing stock. In absolute terms, the greatest savings potentials are in Germany and the United Kingdom mostly due to the large size of their housing stock. Relative to present energy consumption, the greatest savings potentials were identified in Latvia, Bulgaria and Portugal. In general, it seems that cost effective energy savings of approximately 10% can be achieved by 2020 in most countries and 20% by 2030. A total annual energy saving of approximately 150 TWh by 2020 and 280 TWh by 2030 appears possible.