The far‐reaching impacts of climate change have further strengthened the determination of governments around the world to pursue low‐carbon development, and low‐carbon efficiency in less developed regions has become a “shortcoming” in realizing low‐carbon aspirations. We analyze the carbon emission efficiency (CEE) and its temporal evolution in less‐developed regions in developing countries, such as Western China. The differentiation of Western China was evaluated in terms of spatial and influencing factors through the Theil index and the logarithmic mean divisia index (LMDI), and the innovative use of GDP gold content (GDPgc) to represent the absolute economic level in the Theil index. Considering the net carbon emissions (NCE) are undesirable outputs, the GDPgc is taken as the desired output. The Un‐Super‐SBM‐CRS method obtained the net carbon emission efficiency (NCEE) values. The results show that: (1) Western regions’ NCE differences can be categorized as high per capita NCE areas (more than 25 tons), medium per capita NCE areas (10–25 tons), and low per capita NCE areas (0–10 tons). (2) The per capita‐based T (Theil index) and the GDPgc are comparable and “intra‐group convergence and inter‐group differentiation” can be used to describe intra‐regional and inter‐regional NCE differences. (3) Both the level of the economy and the level of urban development are drivers of the 11 domains, and the level of the economy is driven more than the level of urban development overall. There are significant regional differences in other factors. (4) The NCEs and their evolutionary trends in each region can be divided into single‐variable and fluctuating‐variable. © 2024 Society of Chemical Industry and John Wiley & Sons, Ltd.