Abstract: This paper presents an investigation of the impact of different family groups and key energy-related behaviours on the energy consumption of residential buildings through computer simulations. Design of Experiment (DOE) method is used to design the matrix of experiments. The result shows that there is a large variation in the energy consumption per person under different family structures. The energy consumption per person of the retired couples aged over 65 living alone was 1.65 and 1.23 times of the working couples aged between 35 and 64 living with two children and the working couples aged between 25 and 34 with no children respectively,under the same geographical location and the same building characteristics. The results from this study can be potentially used to assist in reliably predicting the most significant factors influencing the energy consumption of residential buildings with different family structure. It is also shown that the development of energy saving policy should consider the variation of geographical location and family structure,occupant age,cooling temperature set-point and air-conditioned area.