Energy self-sufficiency of buildings is based on the production of heat and electricity with the systems which are integrated into the building and utilize renewable energy sources. These systems can be built as decentralized units that are simultaneously converting solar radiation into electricity and heat. Researches shows that high efficiency of both electricity and heat production can be achieved in this way.In the thesis, solutions of integrated photovoltaic and thermal systems using solar energy and their efficiencies are presented, analyzed and compared. A numerical model for determination of effectiveness of the device in the year-round operation was developed and analyzes of possibilities for increasing the effectiveness of the device with concentration of solar radiation are shown.In the thesis we have done a research of the importance of solar energy and it’s relations with other energy sources in Spain, Slovenia and around the world.While researching types and the usage of solar energy, we were focused especially on the use of thermal systems applications with integrated photovoltaic panels (PV-T systems) and the different ways how to increase their efficiency by installing concentrated applications.Finally, a comparison of three different devices for solar energy exploitation (photovoltaic panel, heat exchanger with metal sheet and photovoltaic thermal PV-T) has been done. We studied their behavior in the cities of Ljubljana, Barcelona and Madrid during one year’s period. This study has been made by using of upgraded numerical model developed in the MS Excel program created for a Diploma work “Heat transfer in double ventilated facade” in the University of Ljubljana by Nejc Bozic in December 2009.