Borehole thermal energy storage (BTES) is a long-term energy storage measure. It provides a feasible solution to reduce the seasonal thermal imbalances in buildings by storing renewable or waste heat through vertical borehole heat exchangers. The thermal storage and extraction characteristics of BTES systems are crucial to the heating or cooling performance of buildings. An analytical model is established based on fluid heat transfer within the borehole and transient heat transfer in the surrounding ground. The thermal response of the BTES system is obtained by superposing the excess temperature of individual boreholes in both time and space based on a semi-analytic solution. The borehole wall temperature is used as continuity conditions in calculation to predict the heat storage capacity at different inlet temperatures. The reliability of the semi-analytic model was validated through a borehole charging and extraction experiment. On this basis, the influence of the distance of BTES system on heat storage and extraction efficiency was estimated. The results show that the optimum spacing of heat storage and extraction efficiency is different with different operational years. The optimal borehole spacing increases with the increase in operational duration.