As a leading oil and gas company in middle Europe the OMV AG would like to improve its know-how in the field of geothermal energy. The aim of this thesis is to work out the key performance indicators (KPIs) for geothermal energy projects. Particular attention lies thereby on the technical, the economic, and the political KPIs. In the first part of the diploma thesis the necessary theoretical bases are compiled. The following chapter contains the determination of KPIs on the basis of existing geothermal projects. For that purpose the questionnaire technique and associated evaluations are applied. Supported by the results of this part, a geothermal project, planned in Vienna, is examined economically. With an extensive model built on basis of existing expert's assessments, the net present value of this planned plant is computed. In the following step a deterministic and a probabilistic sensitivity analysis is accomplished in order to examine the single inputs on their influence on the net present value of the project and to find out the KPIs. With these results the KPIs for this and for similar projects are identified. In the last part of this thesis a quantitative evaluation of KPIs is realized for hydrothermal projects. Therefore generalized parameters are inserted into the model calculating the net present value and the KPIs are found out by using a probabilistic sensitivity analysis.