More and more renewable energy units are widely integrated to the power system, resulting in a gradual decrease in the capacity proportion of conventional units with controllable output. Owing to the strong output volatility of wind turbines and photovoltaic equipment generators, the demand for flexible resources in the system is greatly increased. The investment and construction fee for energy storage equipment is expensive. Therefore, determine the optimal configuration capacity of energy storage is necessary. An evaluation method of comprehensive balance capacity for provincial power system considering efficient interaction between source and load is proposed. Its characteristic is to carry out 8760 hours of source-load balance simulation of provincial power grid including energy storage equipment. The system power supply cost is used to determine the configuration capacity of energy storage. Taking the comprehensive power balance problem in Henan Province as an example, the effectiveness of this method is proved by configuring energy storage to meet the power and electricity balance demand in short time scale.