What cause the decline of energy intensity in China's cities? A comprehensive panel-data analysis

China's progress in energy efficiency has contributed significantly to the reduction in global energy intensity (El), but the descending speed of per unit GDP energy consumption in China has been decreasing during recent years. The present study aims to investigate the core driving forces of El from 2005 to 2016 in 289 Chinese cities based on Granger Casualty Test and regression analysis. For this purpose, the study employs panel data analysis with both fixed coefficient and time-varying coefficient which are suitable for examining the effects of influence factors on EI and their change trend. The Granger Casualty Test investigates that there supposed to be a bidirectional causality between air-pollutant emission and energy consumption in China. However, due to China's weak environmental regulations, the negative effect of emission on El is not significant. Further, regression analysis shows that a percentage increase in electricity price decreases El by 0.722% in long-term, but this adjustment takes time. Furthermore, analysis of short-term relationship reveals that optimizing energy structure may be the best way for China to reduce El in short run. Finally, the time-varying coefficients of panel data model indicate that inhibitory effect of promoting electricity consumption on El will keep improving with expansion of electricity use. (C) 2019 Elsevier Ltd. All rights reserved.