Can regional integration narrow city-level energy efficiency gap in China?

Improving energy efficiency is essential for conservation, emissions reduction, and sustainable development. Prevalent huge gaps are not advantageous the improvement of region's overall efficiency. Although studies have analyzed influencing factors regional gap, impact integration on gap remains untested. This paper applies extended stochastic frontier analysis (SFA) method that incorporates time-varying, time-invariant city heterogeneous characteristics to estimate city-level in China from 2005 2017. Building “center-periphery” framework, we further calculate investigate through generalized moment (GMM). The results show 1) average 44.2%, ranging 2.9% 75.5%, indicating has a gap; 2) there U-shaped relationship between within agglomeration. Improvement can narrow when degree low, expand level high; 3) government intervention will smooth Practicable policies mitigate suggested applicable other emerging economies, especially those with imbalance