The development of new energy in developing areas should not only consider the effect on local economic growth, but also give some attention to its spillover effect for economic growth in neighboring areas and take a new path of cluster-style development and cooperative governance. On the basis of Moran’s I and the Spatial Dubin Model (SDM), this paper analyzes the spatial spillover effect of new energy development on economic growth of 21 developing areas in China from 2000 to 2017. The results show that: (1) According to the Moran’s I, there are significant economic agglomeration characteristics in the spatial distributions among different areas in the study area. (2) A comparative study using the mixed Ordinary Least Squares (OLS) method and SDM shows that new energy has a negative spillover effect on the economic growth of neighboring areas when considering spatial factors, but this negative effect is underestimated in the mixed OLS method. (3) In addition to the core explanatory variable, the spatial spillover effect of new energy on economic growth is also affected by control variables, but the degree of impact varies. The results imply that some effective policy measures, such as sustainable development mechanisms, industrial distribution, and comparative innovation, should be taken to encourage new energy development for the high quality growth in developing areas on the national, regional, and global scale.

Improving the efficiency of green development is a crucial step towards achieving the “dual carbon” goal and promoting regional sustainable development. Currently, China has made a decision to foster new quality productive forces, aiming at upgrading traditional productive forces by digitization, which brings new opportunities for urban green transformation. Drawing upon a perspective from new quality productive forces, this paper constructs a framework of impact mechanism about “production factors–productivity–production relations” and uses 108 cities in the Yangtze River Economic Belt to investigate the impact effects, mechanisms, and disparities of the digital economy on urban green development. The research findings indicate the following: (1) The digital economy has a nonlinear influence on green development, with a critical value of 0.149. The conclusion still valid after “Utest” and robustness checks. (2) With the new strategy, digital economy indirectly influences urban green process through nonlinear mediating effects of green technology and green finance, as well as linear mediating effects of resource allocation and industrial structure. (3) There are notable effects heterogeneity across urban agglomerations and individual cities, as well as between resource-based and non-resource-based cities. (4) Furthermore, the policy intensity exerts a stage enhancing effect on the influence. With the promotion of digital policies such as Broadband China, the influence shows a phased increasing trend. The research provides valuable insights for harnessing new quality productive forces to power the digital economy and regional green transformation.