A micro-cogeneration device functions on the basis of an internal combustion engine which powers the electricity generator. Waste heat from cooling of the engine, generator and exhaust gases is used to heat rooms and domestic water or for other purposes, while the electricity generated in this process can be fed into the power grid or used for own purposes. The system is designed to be used in apartment or commercial buildings for bivalent operation in combination with the boiler or other source of heat. Such systems require installation of an intermediate container in order to ensure appropriate heat storage. The control system, installed on the basis of the selected heating curve or flow need required by the client or with regard to the external temperature, is used to control the required water temperature in the heating system.