In order to evaluate the energy performance of the VRV air-conditioning system, a new simulation module is developed and validated experimentally in this study, on the basis of the building energy simulation program, EnergyPlus. The differences between average monitored and predicted data for the total cooling energy and power use are proved to be within 25.19% and 28.31%, respectively. Also, the relative error of power usage simulation follows that of cooling energy closely on an hourly basis. The COP and PLR simulation of the VRV system are also examined, with average error of 6.36% for COP and 18.40% for PLR. It is observed through the test that the energy performance of the VRV system At part-load condition is better than that in the rated condition. (C) 2007 Elsevier B.V. All rights reserved.