Authors carried out analyses to determine the influence of parallel and series connection of high-tem- perature installations with low-temperature installations on improvement the utilisation of geothermal energy in a geothermal heat plant. The main purpose of this work was to evaluate how much the application of the low-temperature heating systems has an effect on the influence on the degree of the geothermal energy in the geothermal heat plant, which supplements the heat distribution network supplying two groups of heat receivers having the distinct shares in a heat consumption. These studies are very interesting because concern the possibility of modernisation the heating systems by application the geothermal unit in a conventional heat plant.