Many countries, especially in Europe, have ambitious goals to transform their national energy systems towards renewable energies. Technological change in both renewable production and efficient use of energy can help us to make these targets come true. Using a panel of German firms linked to the PATSTAT patent data, we study inventions in both types of energy technologies and investigate the role prior inventions as technology-push factors play for both types of technologies. In addition and more importantly, we study whether previous inventions in non-energy technologies also stimulate technical change in energy technologies and whether this effect differs between energy conservation and renewable energy technologies. (C) 2015 Elsevier Ltd. All rights reserved.