The optical analysis of a concentrating photovoltaic system plays an important role in determining its overall performance. Typically, ray tracing with a standard AM1.5 source spectrum is utilized to carry out this process. However, this does not represent the actual operating conditions experienced by the device. The solar spectrum changes depending on the time and geographic location. In this work, we propose and demonstrate a procedure to include the changing solar spectrum whilst predicting the annual performance of a building integrated concentrating photovoltaic system. Using a statistical approach a frequency of occurrence of the different solar spectrum is estimated for different locations and utilized for carrying out the annual performance prediction of the system. It is found that using the standard spectrum underestimates the actual system performance. The highest optical efficiency of 79.8% was observed for Kemi when considering the actual spectrum values. This value was found to be 1.6% higher than that obtained using AM1.5D spectrum. An average difference of 1.25% was found in the annual performance of the system when evaluated for six different geographic locations. (C) 2015 Elsevier Ltd. All rights reserved.