In this paper, solar data derived from METEOSAT images are used to design stand-alone photovoltaic systems. Using a combination of both daily WEFAX satellite images and a TAG model, hourly global solar irradiation data on a horizontal plane are synthesized with a good accuracy (RMSE<80 Wh m(-2)). Then, adding the Hay and Hollands＇ correlations, generic hourly irradiances on tilted planes are computed and used to size stand-alone PV systems.