My task was to define the consumption of a previously established KNX/EIB building automation system and the additional type GIRA Homeserver in addition to determining the sustainability and the return of the system. I am mainly focusing on presenting the essential functions of the KNX/EIB system. Moreover, I am presenting the details of the consumption of an average family house and its devices. I am also going into the energy-saving opportunities of the two systems. I am also outlining the establishment of the measurement and its results. From this data, in addition to the information received from other companies in the field, I am drawing a conclusion with summarizing my results. Standard meters were used for the measurements. Predicting the expected result, our system will presumably save the amount of energy it consumes but the main question is if our investment pays off in the long term. We are trying to find an answer for this question. And fortunately, with the help of hungarian companies, we will have the answer at the end.