The performance of a flat plate solar collector with thin absorber is studied. The temperature of the absorber and its variation along the local day time is obtained by solving a heat balance equation. The temperature of the working fluid is also estimated. A published solar source functionto predict the hourly daily incident solar irradiance on horizontal surface is considered. Five absorbers of different materials: Copper, Aluminum, Stainless steel, Glass and Mica are treated. Two cooling conditions at the absorber front irradiated surface are also taken into consideration. Factors affecting its efficiency are revealed.