Solar energy, owing to its emission-free properties and environmental sustainability, has been extensively explored for integration into buildings. Building-integrated photovoltaic (BIPV) technology contributes to energy conservation and emissions reduction by combining electricity generation with architectural design. However, conventional solar buildings face challenges related to single functionality, suboptimal photoelectric conversion, and a significant increase in space cooling load. In response, a semi-transparent BIPV window system combined with an air-conditioning system is proposed as a promising solution to improve comfort levels and reduce energy consumption. This study aims to provide valuable insights into optimizing system designs for achieving more energy-efficient buildings. The focus is on evaluating the energy and daylight performance of this combined system for various window-to-wall ratios (WWR). Electrical and thermal performance is simulated and assessed through solutions of the energy balance equations for each component of the system in the Matlab environment. Daylighting simulations are conducted using Design Builder software to analyze the distribution of natural light in indoor spaces and thus artificial lighting demand. Furthermore, the influence of WWR on the energy benefits and consumption of a typical office integrated with this system is investigated for three typical cities in China with hot-humid weather conditions. Results show that with a relatively large WWR (WWR ≥ 60%), the application of the system in the building offers better overall energy performance.