The existing stock of institutional buildings constructed before current thermal regulations is known to be high-energy consuming. In several cases, those dedicated to education and research in particular, contribute to a large share in local authorities' expenses. The high consumption levels are due in general to low thermal regulations requirements and to the diversity of occupants, occupancy profiles and used equipment. We hereby report on a comparative study of the energy consumption of three campus buildings covering more than 50,000 m² useful ground area and situated in Paris region. Used data were collected during more than three years between 2014 and 2017 and at different time scales, from a yearly time step down to 10 minutes. Statistical analysis tools are used, to identify the main energy drivers and their relative weight in the overall energy consumption for instance. The impact of different thermal regulations is clearly assessed through a post occupancy study. Together with equipment, occupancy is shown to be the main electric energy consumption driver. The introduced tools lay the ground for a non-intrusive method for large tertiary buildings power demand curves decomposition and reconstruction.