Heat demand reduction and cogeneration are two main options to reduce fuel consumption for space heating and warm tapwater in buildings. This article compares fuel saving and costs of these two options for the case of new Dutch houses. In the calculations, simulation techniques are used to account for diurnal and seasonal variations of both the heat demand level and the operational conditions of cogeneration. The use of a short term thermal storage is considered in order to match heat supply and demand. Heat demand reduction and cogeneration appear to have a considerable fuel saving potential in new Dutch houses. At present Dutch natural gas prices both options are not cost-effective. However, expected investment cost reductions and energy taxes that are under consideration may eliminate this hindrance. These developments would also open possibilities towards combinations of heat demand reduction and cogeneration. Such combinations could make a large contribution to fuel consumption reduction goals in The Netherlands.