With the development of energy storage technology and decrease of energy storage cost, energy storage has become an important means of load control. The economic benefits of energy storage allocation in power demand side are evaluated. Firstly, the cost calculation model considering the whole life cycle is established. Secondly, the benefit calculation model is established from four aspects of grid side, user side, power side and policy subsidy.Finally, it is concluded that this energy storage can obtain good economic benefits through example analysis. In addition, it is concluded through sensitivity analysis that factors such as energy storage cost, peak-valley price difference and policy subsidy have a great impact on the economy of energy storage system.