System reliability under varying weather conditions and the corresponding system cost are the two main concerns for designing hybrid solar-wind power generation systems. This paper introduces the Hybrid Solar-Wind System Optimization Sizing (HSWSO) model, to optimize the capacity sizes of different components of hybrid solar-wind power generation systems employing a battery bank. With the incorporated HSWSO model, the sizing optimization of hybrid systems can be achieved technically and economically according to the system reliability requirements. A project case is chosen and simulated to show the importance and reliability of the HSWSO model for sizing the capacities of wind turbines, PV panel and battery bank of hybrid solar-wind systems. The results give the optimal configurations of the hybrid system with the lowest LCE according to the desired system reliability requirements for the demand load. The weighting relationship among three sizing parameters is discussed accordingly. This paper also investigates the influence of the prices of batteries and PV modules on the optimal sizing and the LCE calculation.