This paper presents results obtained from a practical study of photovoltaics in buildings, in rural England and a computer model simulation study in Malaysia. It is a particular application of Building integrated PhotoVoltaics (BiPV) where the PV modules are fitted as partial roofing material. Data from a monitored BiPV-UK installation were analysed and compared with PVSYST 2.0 predictions. This computer model was then used to simulate BiPV applications for the standard school building in Malaysia, enhanced with a thermal computer model SUNREL 1.0 beta. Whilst cost-effectiveness has been a major issue in its proliferated use, the technology has been without doubt established. Based on the simulated system performances, it can be seen that the application of BiPV technology in Malaysia seems to offer a much better potential as has been expected.