This thesis shows the energy - economy analysis of the separation of the residential building from the district heating and the transition to its own thermal system. This thesis analyzes the proposals for a new heat generator, and the option of installation of thermal insulation. Before the analysis could be accessed, it was necessary to determine the annual useful energy for heating and cooling, as well as for heating of domestic hot water. Software KI Expert Plus was used for this purpose. Three generators of heat were taken into account: a gas boiler, an oil boiler and a heat pump. All heat generators were analyzed in combination with thermal insulating from 0 cm to 15 cm thick. The goal of this paper was to determine the system that will have the lowest cost over a period of 20 years, for the lowest annual primary energy consumption. For each of the three proposed heat generators, the annual primary energy consumption was calculated in relation to the insulation thickness and the total investment costs and the cost of running the system is calculated. Based on the data obtained, the optimal system was chosen as a replacement for the district heating system