This study investigates the impact of occupancy assumptions on the accuracy of simulated energy performance of Australian office buildings in the design stage. The first part of this paper will present the results of occupancy surveys of a limited number of Australian office buildings performedby the author.

The second part of the paper utilises the data from the occupancy surveys to quantify the difference between the predicted energy performance of buildings using a range of values for occupancy based on the surveys and the predicted energy performance of the same building models using the National Australian Built Environment Rating System (NABERS) occupancy assumptions. The study aims to determine if use of the NABERS assumptions causes significant distortions in modelled energy performance.