During last few decades the phenomenon of global warming up of the atmosphere is discovered. It is also concluded that the climate in cities changes, the main result of what is the higher air temperature, the heat island within the places with cold weather. This happens also in Belgrade. There are many reasons for this phenomenon, but the anthropogenic production of energy is considered to be one of the main factors for the rise of temperature. The aim of this work is to define anthropogenic sources of heat in Belgrade and to reckon the quantity of heat they emit as additional sources in relation to the sun.