This paper presents monitoring results of two examples of building integrated PV system investigated at the School of the Built Environment, University of Nottingham in the UK. One of the systems is installed on an educational building, and consists of a thin film PV facade appropriate for commercial or office suites. The other system is installed on a detached house, and uses crystalline PV roof slates, appropriate for domestic buildings. As the two buildings are significantly different in size, construction and occupancy, the design and selection of the PV system for each was also different. The monitoring investigation has assisted identification of shortfalls in performance and possible explanations have been suggested. The results presented in this paper provide information on the design process, and highlight similarities and differences in the design, installation, performance and economics of the two systems. (C) 2003 Elsevier Science Ltd. All rights reserved.