In the process of low-carbon construction of integrated energy systems, the analysis of the system's low-carbon level and the determination of factors influencing the system's low-carbon development potential are considered to be a challenge. Therefore, a comprehensive low-carbon assessment method for integrated energy systems based on the hybrid variable-rights theory was proposed. Firstly, the current development of smart grid was taken into account, and a low-carbon integrated assessment system including carbon capture and demand response technologies was also proposed. Pearson coefficients were utilized to conduct correlation analysis of the indicators within the system. The weights of the indicators were updated using a subjective and objective combination assignment method improved by the hybrid variable weight principle, taking into consideration the ranking of the multi-dimensional indicator state values. Secondly, a technique for order preference by similarity to ideal solution (TOPSIS) model based on hybrid variable weights was established to comprehensively assess the influencing factors of the system's low-carbon level and low-carbon development potential, providing a more scientific and objective basis for seeking carbon reduction paths and achieving the construction of the system's decarbonization. Finally, the data of the integrated energy system in the northern region of Xinjiang were selected for arithmetic analysis to verify the correctness of the proposed method.