With a strong commitment to sustainability, numerous universities set their carbon reduction targets, with the common measure being energy retrofitting of their campus buildings. Based on a complex understanding of the higher educational buildings’ energy consumption characteristics, this study addresses the role of the academic calendar that regulates the occupancy condition of campus buildings and consequently determines their energy consumption. Using an Australian university as a case study, the research collected energy data from its 122 campus buildings, analysed the data regarding the occupancy condition, and compared the data under two different academic calendars: semester and trimester. Among all campus building types, those used for teaching had the highest energy use, accounting for more than 50% of the whole campus energy consumption. Buildings that are used for research had the highest energy use intensity, at more than three times that of teaching. From a semester to a trimester academic calendar, the campus energy showed a reduction by 213,090 kWh per year (around 5% reduction). The energy consumption of teaching dedicated space decreased by 505,521 kWh per year (around 3% reduction), while that of research increased by 153,893 kWh per year (around 2% reduction). This indicated a decrease in teaching equivalent to an increase in research activities when transitioning to a more flexible enrolment calendar. The results suggest that the pattern of the occupancy condition regulated by the academic calendar should be adequately captured in the campus energy management and carbon reduction policy.