Solar panels are one of the most promising renewable technologies for energizing future buildings. For roof top solar panel installations, knowledge of the optimum tilt angle is important to have the maximum annual or seasonal energy yield. The annual optimum tilt angle is dependent on many factors such as the latitude of the location and the weather condition. In an urban application, the optimum tilt angle can be affected by the surrounding obstacles. Consequently, new concerns such as shading or sky blocking effects have to be taken into consideration. In this paper, a simple method is proposed based on a modified sky model to calculate the optimum angle of installation for the urban applications. The obtained results demonstrate the dependency of the optimum angle of installation on the latitude, weather condition and surroundings. (C) 2012 Elsevier Ltd. All rights reserved.