Various types of silicon-based photovoltaic modules were installed at the same outdoor exposure site in Japan. The output parameters of the modules were measured and also incident irradiance, incident spectrum, and module temperature were recorded at the same time. A statistical analysis method has been proposed to separate the influences of spectrum variations and module temperature variations on the output performance of the modules. Moreover, with this method, the performance of polycrystalline silicon, amorphous silicon, and three-stacked amorphous silicon photovoltaic modules were analyzed. (c) 2006 Elsevier B.V. All rights reserved.