Deploying coal for grid flexibility increases power sector costs for China’s carbon neutrality

Decarbonizing power systems with high shares of solar and wind requires enhanced grid-balancing strategies. In China, current policy emphasizes deploying new coal-fired power plants to provide dispatchable flexibility, yet quantification of their effectiveness and implications relative to alternative options remains limited. Using an integrated modeling framework, we compare coal-based and alternative grid-balancing strategies for the China Southern Power Grid (CSPG) under two decarbonization pathways. We find that deploying nearly 50 GW of planned coal capacity in CSPG increases system costs by 11–19%, results in substantial underutilization of the coal assets, and delivers limited reliability benefits. In contrast, solar and wind supported by hydropower and battery storage supply most future electricity demand at lower costs, while a modest contribution of fossil-fired generators with carbon capture and storage further enhances operational efficiency by reducing battery dependence and curtailment.