Abstract: After the integration of renewable energy into the power system, conventional power sources are needed to help balance its randomness and variation, which results in the balancing costs. It is of great significance to analyze and calculate the balancing costs to promote the rational allocation of returns between renewable energy and conventional power sources. The system balancing costs are decomposed into the incremental reserve costs, the secondary frequency regulation（SFR） costs and the incremental electricity energy costs caused by the renewable energy accommodation. Based on the “load-following transform”method, a virtual scenario of renewable energy with no fluctuation relative to load and no need to provide reserve and SFR capacity is constructed, and a calculation method for the system balancing costs based on scenario simulation and comparison method is given. The calculation and analysis results of the balancing costs of the modified IEEE 39-bus system verify the rationality of the proposed method.