The simulation model for performance of chiller (ASHRAE model in this study) disclosed in ASHRAE Guideline 14 in 2002 is implemented in Taiwan to verify the efficiency of energy-saving methods adopted by energy service companies (ESCO). Since the accuracy of the simulation model for performance of chillers has influenced on the promotion of the ESCO business, the author used practical measurement data to compare the accuracy between the ASHRAE model and the commonly used energy consumption model of chillers (XY model in this study) and concluded that the XY model had much higher accuracy than the ASHRAE model.