Minimum allowable values of the energy efficiency and maximum energy efficiency grades are analyzed for room air conditioners in China and several ASEAN members. The profiles of cooling hour vs. temperature corresponding to those weather conditions in several cities of China and ASEAN are figured out, and then the seasonal energy efficiency ratio (SEER) and thermodynamic perfectibility for room air conditioners under those weather conditions are discussed. SEER and thermodynamic perfectibility are different for air conditioners with the same energy efficiency ratio (EER) running in diverse climatic areas. As far as numerous air conditioners operating in a certain climatic area are concerned, the higher EER for a given air conditioner, the higher SEER and thermodynamic perfectibility. Nevertheless, there are obscure rules between SEER and thermodynamic perfectibility. No matter what energy efficiency indicators such as EER, SEER or thermodynamic perfectibility are selected to evaluate the energy performance of room air conditioners，the energy efficiency level in China is the highest among China-ASEAN region.