As the demand for sustainable energy solutions grows, photovoltaic windows (PV windows) have gained significant attention as an emerging building integrated photovoltaics (BIPV) technology. This is due to their dual potential in reducing building energy consumption and providing renewable energy sources. This study aims to propose an analytical solution for the energy assessment model of semi-transparent photovoltaic insulating glass units (STPV-IGU) by simplifying the thermal balance equation nodes. The efficacy of the proposed model was validated through comparison with experimental data, demonstrating a high degree of congruence. Additionally, an equivalent electrical method is employed, which uniformly converts non-electric forms of energy into electrical energy according to possible conversion coefficients. Taking Shanghai as an example, a comparative analysis of the annual energy performance of the south-facing window system for STPV-IGU and double-glazed insulating glass units (DS-IGU) was conducted. The results show that the annual net electricity consumption of STPV-IGU is -11.5 W/m², while that of DS-IGU is 22.3 W/m², indicating that STPV-IGU has substantial energy-saving potential.