“…To make a thorough inquiry of the regional disparities in power efficiency, we divide China into six major regional power networks based on the classification standards of regional power networks, i.e., Northeast, North China, Central China, East China, South China, and Northwest. The regional efficiency level of MTE and ETE from high to low is East (Central) China, Central (East) China, South China, North China, Northeast and Northwest, and the conclusion has been confirmed by other studies [38]. It shows that the ranking of MTE hardly changes after the inclusion of environment constraints, as shown in Table 3 and Figure 2.…”