Daylighting strategies in building design can lead to reduce of the energy consumption for electric lighting. However, the potential energy saving for electric lighting is highly dependent on user’s behaviour. While in office buildings the standardized user’s behaviour reveals a robust correlation between daylight availability and the electric lighting energy use, in residential buildings this relationship is not so straightforward. The aim of this study is to investigate if the availability of natural light is related to a decreasing of the electric energy use for lighting, analysing the actual users’ behaviour in three different rooms of a single family house in Trondheim (Norway).