During the actual operation of an ASHP unit installed in different climate regions, ambient operating conditions can vary constantly over an entire heating season, thus the actual output heating capacity of ASHP units may vary significantly from region to region. To enable a convenient evaluation of output heating capacity of a space heating ASHP unit installed in different climate regions, regional performance evaluation indexes including $\overline{T_{\text{a}}^{\prime }}$, HERR_(Ta’), β_Ta and β_RH based on ETD method have been developed. These evaluation indexes are generalized and can be used to evaluate the regional performance of ASHP units operated in any regions. It can also be used to specify the key factors affecting the operating performances of ASHP units in different regions. With the developed evaluation indexes, the regional operating performances of ASHP units installed in 278 Chinese cities were evaluated. The results demonstrated that the total output heating energy for ASHP units operated in Southern Chinese provinces may be lower than those in Northern China. In Shanghai, $\overline{T_{\text{a}}^{\prime }}$ at −6.0 °C is lower than that at −3.0 °C in Beijing, suggesting the total output heating energy from an ASHP units operated in Shanghai over an entire heating season would be lower than that in Beijing. Furthermore, in southern Xinjiang and northern Fujian Provinces, the total output heating energy from ASHP units may be higher than those operated at the nominal condition. In addition, in Tibet, Beijing, Liaoning, etc., the total output heating energy from the ASHP units would be affected more by T_a, thus ASHPs’ manufacturers are recommended to develop ASHP units suitable for operation in low temperature ambient. In most regions in southern China, RH would affect more on the total output heating energy from the ASHP units, thus ASHPs’ manufacturers are recommended to develop ASHP units having frosting suppression provisions and accurate defrosting measures.