As a major greenhouse gas, carbon dioxide emissions (CO2E) are the main cause of global warming and environmental pollution. Thus, the reduction in carbon emissions has become a global concern. The widespread use of renewable energy and the improvement of energy efficiency seem to provide a feasible path for countries to achieve carbon emissions reduction, and have received the attention of governments and academics. However, very little literature has focused on the spatial and temporal heterogeneity of the effects of renewable energy use and energy efficiency on carbon emission intensity. This study applies the geographically and temporally weighted regression (GTWR) model and complies with a balanced panel of data from member countries of the Regional Comprehensive Economic Partnership (RCEP) between 2000 and 2019 to investigate the spatiotemporal heterogeneity of the effects of renewable energy and energy efficiency on CO2E. The results show that CO2E per capita (CO2EP) increases over time, but its distribution across RCEP member countries remains largely stable. Overall, the usage of renewable energy tends to decrease CO2EP, while energy efficiency tends to increase it. However, with the passage of time and changes in geographical location, renewable energy consumption and energy efficiency show significant temporal and spatial heterogeneity in their effects on CO2EP of RCEP member countries. Additionally, the effects of industrial structure, merchandise trade, urbanization rate, and energy poverty on CO2EP of RCEP member countries are also characterized by spatial and temporal heterogeneity.