The work deals with usage of heat energy from cogeneration unit in a family house. It is focused especially on the use for family house's heating and warming of service water. Optimalization is made on existing cogeneration units. In this work we will handle with two types of cogeneration units of different capacities. From the beginning we concern in current situation and the possibilities of regulation. Further we deal with the possible ways of optimalization of winter and summer running and with the costs for these optimalizations.