Due to the increasing relevance of renewable energies within the society, aiming for an alternative to fossil fuels, geothermal energy becomes more and more attention. The aim of this thesis is to observe the thermic efficiency of a geothermal well TH1 within the city of Munich, planned, executed and operated by Erdwerk GmbH. The well TH1 has a depth of 3860m MD and a TVD of 2809.2m and an average reservoir temperature of 109°C. Geothermal energy, especially in the context as a replacement for fossil fuel sources and renewable, “clean” energy, has gained in significance in recent times. The following methodology includes the construction of a mathematical model of the well via the utilization of the Wolfram Mathematica software program, in order to establish final wellhead temperature through the estimation of the thermal losses during production. The main part of this methodology is the calculation of the heat losses during production, as these occur radial and via steady state within the tubing, cement, casings and annulus and via transient state within the formation. Additional purpose of the model’s construction, was to gain insight as to the impact of certain parameters, thus developing, adapting and implementing possible improvements and solutions strategies for future and current projects. The focus thus was not only on variable parameters but extended to the environment and the trajectory of the well and their influences on the temperature of the produced fluid at the wellhead. Hence, it is important to note, that this model neglected pressures and their accompanying effects such as free gas, as this would certainly exceed the extent of this thesis.