Reducing energy consumption is one of the essential global assignments since modern society is facing problems of the increasing population, limitation of energy resources, and climate changes. Decreasing the CO2 gas emissions, protection of the environment, as well as financial benefits, are one of the most significant consequences of applying the principles of energy efficiency and sustainable development. As in other developed countries, the Republic of Serbia's total energy consumption has been steadily increasing over the last decade. The largest share of this consumption is in the residential and commercial buildings (35-40%), while in other sectors, primarily industry and transport, it is slightly smaller.