The present study analyzes the correlation between the optimal angle for a fixed Building Integrated Photovoltaic (BIPV) system and the latitude of the system's site as measured in degrees according to estimates made with PVSYST 3.41 software. Calculations were made for a BIPV south orientated tilted roof at 20 different locations in 14 countries, ranging from 0 degrees to 85 degrees, latitude in the Northern Hemisphere. In order to prove the reliability of using the latitude angle as the angle for the tilted panel, the correlation was made between the performance obtained with the system using the optimal angle and the system with the site's location angle. Results indicate that an average of 98.6% a system's performance with the optimal angle can be obtained using the latitude angle for the tilted panel. (C) 2008 Elsevier Ltd. All rights reserved.