In this paper, we apply the functions of innovation systems theory to explain the successful, diffusion of cogeneration technology in The Netherlands. We show that the technological innovation system for cogeneration functioned very well and that this explains for a major part the successful diffusion. We also show that the innovation system was positively influenced by actions of the Dutch government. Government actions were aligned to the needs of the other parties in the innovation system. Finally, we show that part of the successful diffusion can be attributed to changes in the institutional environment that were not intended to stimulate cogeneration. (C) 2007 Elsevier Ltd. All rights reserved.