Study on Energy Efficiency Testing Method of Window Mounted Ventilating Fans Window mounted ventilating fan is a common appliance to keep good air exchange for household and dining uses. This paper focuses on experimental study of energy efficiency testing method for these ventilating fans following international standards ISO 5801 and AMCA 210. This study also provides the performance data of a standing electric fan sample to explore the difference of air flow rate measurement between ISO 5801/AMCA 210 and CNS 547, which applies to the electric fan testing in Taiwan. Finally, here finishes the test for 19 samples and conducts a suitable energy efficiency draft for the voluntary ”Energy Label” program to run in the future.