Mathematical model is presented for prediction of thermal losses from central receiver solar thermal power plant. Results obtained are verified with evidence from solar experiments. Code is developed for studying the effect of variation of weather conditions i.e. variation of incident solar radiation, wind speed and ambient temperature during the entire year on the thermal performance of receiver. Thermal losses have its effect on efficiency of the receiver and hence the overall cost of solar thermal to electric power. Radiation and convection losses are the major components of thermal losses. Simulation is done for weather data of Jaipur city of India