The installation of common solar panels and collectors in the built environment requires access to significant roof space, which is limited. This motivates the development of high-efficiency, building-integrated technologies that can maximize space utilization and energy provision. In this work, a building-integrated hybrid photovoltaic-thermal window (PVTW) is fabricated and tested, composed of a semi-transparent photovoltaic (PV) layer and a selectively absorptive liquid-based thermal absorber. It is demonstrated that, at 30° inclination, the PVTW can simultaneously generate electricity, with an electrical efficiency of 3.6%, and provide ≈50 °C water, with a thermal efficiency of 10.7%, in the middle of a typical summer day (20th July) in London (maximum ambient temperature ≈34 °C, solar irradiance ≈1100 W m−2 at midday). The water temperature decreases by ≈7 °C, whilst thermal efficiency improves to 17.6% as the inclination angle increases to 90° (vertical); the electrical efficiency reduces marginally (3.3%). Compared to a liquid-based solar-thermal window (STW), the PVTW can generate hot water at ≈10 °C higher temperature and with 10% absolute increase in thermal efficiency when the inclination angle is 60°, plus electricity. The wider uptake of this technology in glass-based urban spaces has the potential to generate significant energy while reducing building temperature management costs.