Flat Plate Collector (FPC) is widely used for domestic hot-water, space heating/drying and for applications requiring fluid temperature less than 100°C. The absorber plate of the FPC transfers solar energy to liquid flowing in the tubes. The flow can takes place due to thermosyphon effect or by forced convection. However, certain energy absorbed by the plate is lost to atmosphere due to higher temperature of the plate. The collector efficiency is dependent on the temperature of the plate which in turn is dependent on the nature of flow of fluid inside the tube, solar insolation, ambient temperature, top loss coefficient, the emissivity of the plate and glass cover, slope, etc. The objective of the present work is to evaluate top loss coefficient considering these aspects of the flat plate collector both theoretically and experimentally. A test setup is fabricated and experiments conducted to study these aspects under laboratory conditions. © 2006-2009 Asian Research Publishing Network (ARPN).