A method of calculating underground storage temperatures during the operation of a geothermal plant with a circulation system via at least one geothermal probe or an energy pile with inlet and outlet lines leading to the geothermal probe or energy pile, wherein the underground temperature in the underground storage and/or the temperatures at the inlet and outlet lines are measured, having the steps: - creation of an underground storage model for conversion of the measured temperature profiles to dynamic energy flows in the underground storage; - creation of an energy flow model based on statistically determined patterns and on influencing variables relevant from a thermic and cooling point of view; and - calculation of the future temperature profiles in the underground storage using the energy flow model and the underground storage model. characterised in that the calculation of the dynamic energy flows in the underground storage from the measured temperature profiles takes place by a step-by-step procedure, wherein the current change in the measured temperature is determined in a specific time step and this is corrected by the temperature effect of all energy flow changes in the preceding time steps, whereby at the end of the present time step there remains only a temperature change which is solely an effect of the energy flow change at the start of the present time step, whereby the energy flow change of the present time step is calculated and there is advancement to the next time step, whereby there arises a time series, based on the measured temperature profiles, of the energy flows in the underground storage, wherein recurring patterns, namely annual, weekly and daily cycles of the energy flows in the underground storage, are taken into account for creation and parameterization of the energy flow model and the energy flows to be expected in the future are simulated using the energy flow model and expected future input quantities and parameter values for operative management and utilization of the plant, the outside air temperature and further microclimate data and/or weather data as well as a possible stressing of the underground storage by neighbouring plants. - creation of an underground storage model for conversion of the measured temperature profiles to dynamic energy flows in the underground storage; - creation of an energy flow model based on statistically determined patterns and on influencing variables relevant from a thermic and cooling point of view; and - calculation of the future temperature profiles in the underground storage using the energy flow model and the underground storage model. characterised in that the calculation of the dynamic energy flows in the underground storage from the measured temperature profiles takes place by a step-by-step procedure, wherein the current change in the measured temperature is determined in a specific time step and this is corrected by the temperature effect of all energy flow changes in the preceding time steps, whereby at the end of the present time step there remains only a temperature change which is solely an effect of the energy flow change at the start of the present time step, whereby the energy flow change of the present time step is calculated and there is advancement to the next time step, whereby there arises a time series, based on the measured temperature profiles, of the energy flows in the underground storage, wherein recurring patterns, namely annual, weekly and daily cycles of the energy flows in the underground storage, are taken into account for creation and parameterization of the energy flow model and the energy flows to be expected in the future are simulated using the energy flow model and expected future input quantities and parameter values for operative management and utilization of the plant, the outside air temperature and further microclimate data and/or weather data as well as a possible stressing of the underground storage by neighbouring plants.