Abstract: Given that the impact of initial investment in energy storage as well as its operational costs and revenues on the overall economic benefits of the integrated project are of vital importance, this paper proposes an investment benefit analysis method in which the operational profit of energy storage for park-level projects is taken into full consideration under the user's independent investment operation mode. Firstly, based on the operating characteristics of energy storage, quantitative models are constructed for typical-day residual photovoltaic (PV) charging/discharging volumes and peak-valley arbitrage electricity quantities in park-level energy storage. Secondly, models for various revenue sources within the project are presented. Then combined with the analysis of the investment and operating costs, a comprehensive investment return analysis model that accounts for the operating benefits of energy storage is proposed. Finally, the effectiveness of the proposed model and methodology is validated through the case study of a comprehensive park project in Shanxi Province. Simulation results show that with the internal power source primarily photovoltaic, considering the optimization objective of the overall system benefit, the optimal source-to-load ratio for the project should fall within the range of 2∶1 to 3∶1, and the energy storage configuration should account for 10% to 25% of the total installed PV capacity.