This report provides information on the design and operational factors affecting the performance of photovoltaic (PV) systems in non-domestic buildings. It is aimed at decision makers, developers, architects and engineers involved during the conceptual stages of PV projects on buildings, and will inform system design decisions at the earliest stages. The report uses monitoring data from real buildings and recent research. It focuses on commercial systems but also draws on experience in the domestic sector. Appendices contain background information on PV for those in the building industry with limited knowledge of the technology and its use in building systems. The report does not aim to be a design tool but provides key information for use in developing a PV building project in order to help maximise energy generation performance. It reviews the background to PV systems, performance measurement, their use in buildings, including building integration methods, performance design choices and operational issues affecting performance as well as system costs and carbon savings.