The energy-saving performance of different air economizers (i.e. TEC and HEC) have been investigated in a VAV AC system under different climatic conditions of China based on the year-round energy consumption model developed in this study. According to the calculation results, the air economizers will achieve a higher energy-saving ratio (ESR) in the southern cities of China (char- acterized by hot-humid climatic condition) than applied in the northern cities of China (characterized by dry-cold climatic con-dition). Specifically, it is more energy-efficient to use the HEC scheme under hot-humid climates and to use the TEC scheme under dry climates. Comparing the enthalpy of outdoor air with that of recirculating air needs more sensors (temperature and humidity sensors) than comparing the temperature of outdoor air (only tem- perature sensors required). It is simpler and more convenient to implement the TEC control in the actual situations. Therefore, the TEC scheme should be top-priority in locations having dry climates. While for hot-humid areas, whether or not the HEC scheme is used instead of the TEC one depends on the further investigation on how much more benefit can be gained from HEC than TEC. In addition, the indoor air temperature is the key parameter to influence the energy-saving performance of both the air economizers. Higher indoor air temperature set-point in cooling season will be surely beneficial to the energy savings of VAV AC systems combined with air economizer cycle.