The present work undertakes a theoretical and empirical study of the influence of occupants’ behaviour on energy consumption of domestic buildings. The calculated energy consumption of a number of almost identical domestic buildings in Denmark is compared with the measured energy consumption considering the influence of occupants’ behaviour. The sensitivity and uncertainty related to occupants’ behaviour – among other parameters - are determined by means of stochastic modelling based on input distributions found by literature study, industry guidelines, measurements and simple assumptions. A high number of parameters are investigated and ranked in terms of variance and importance to determine which ones contribute the most to the overall level of uncertainty. It is found that the temperature set point and occupant heat load are substantial contributors to the uncertainty. The major part of the variance can be assigned to the occupants’ behaviour.