After a three-year trend of flat or slightly decreasing CO2 emissions in China, carbon emissions rose again in 2017. This was mainly driven by the construction of additional coal power plants, resulting in large uncertainties regarding China’s future emission trajectories. This paper focuses on the uncertainties, including potential carbon ‘lock-in’ effects, for the Chinese power sector regarding the development of future coal power plants. This is accomplished through the development and application of a technology-rich bottom-up energy system model. Several scenarios were constructed to investigate the impacts of different future power sector pathways on China’s peak CO2 target. The results show that peaks occur at three different times based on different conditions: (1) If more coal power plants are added in the 13th (2016–2020) and 14th (2021–2025) five-year plan periods, it is likely that China will reach peak CO2 emissions around 2025–2035, (2) if coal power plants operate at higher utilization rates, the emission peak is more likely to occur later, between 2030 and 2035, and (3) if renewables are given more priority in the grid and operate at higher utilization rates, it is likely that China will reach peak emissions between 2025 and 2030. Moreover, if more stringent controls on coal capacity are implemented after 2020 and the rate of utilization of renewable power plants improves considerably, it is likely that the peak will occur earlier (between 2020 and 2025). Based on our results, we suggest that governments should integrate plans for investments in coal power plants into long-term emissions mitigation strategies and implement regulations to optimize their country’s power generation structure.