Evaluation of transmission and distribution cost rationality of power grid enterprises enables governments to scientifically approve power transmission and distribution prices. To depict the impact of environmental differences of power grid enterprises on the evaluation of operational efficiency, we measured and calculated meta-frontier efficiency and group-frontier efficiency of 25 provincial-level grid enterprises in China, from 2016 to 2019, by building a meta-frontier-based super-efficiency DEA model, and ranked them based on meta-frontier efficiency, in this paper. The measurement results show that there are pronounced differences in the operational efficiency levels of power grid enterprises, which are not only related to objective differences in economic development level, geographical environment, and historical burden, but also related to technology and management levels of individual enterprises. The cost rationality evaluation method proposed in this paper lays a foundation for introducing "cost benchmarking" in future power transmission and distribution pricing, providing reference for perfecting the transmission and distribution prices regulatory mechanism.