In the last decades, the number of geothermal heat and power installations worldwide increased and despite recent drawbacks, the trend seems to continue. In Germany, three regions qualify for the installation of deep hydrothermal geothermal wells: the Upper Rhine graben, the north German Basin and the south German Molasse Basin. 26 deep geothermal projects have been realized in the German Molasse Basin between 1998 and March 2018. In this paper, we provide an analysis of the current status of those southern German deep geothermal projects. The existing 26 hydrothermal geothermal projects have been evaluated in an empirical approach with respect to drilling success and related costs. Analysis show an overall average drilling rate of 43 m/d. Comparing heat and power projects, heat projects show a slightly higher drilling rate with 47 m/d compared to 39 m/d for power projects. Based on the available data the success rate for heat projects including sidetracks and deepenings is 100%. For power projects the success rate is 75%. Analysis show that thus far there are two reasons that lead to unsuccessful projects in Bavaria: insufficient yields and for one project the natural gas content. Overall three projects were unsuccessful, which were all power projects and situated in the deeper southern part of the Molasse Basin. We find that a differentiation should be made between projects that are designed for heat and those that are designed for power production. Naturally, power projects aim at more ambitious target reservoirs at greater depths and require relatively high yields. This causes quite elaborated and rather long (sub-)horizontal drilling paths within the reservoir rock formation. Regarding the drilling success rate, our study shows that the success rate of first-try boreholes for heat projects with 94% is three times higher than for power projects with 32%. The probability of encountering low yields or technical drilling problems increases beyond 3000 mTVD from 4% to 49%. Apart from exploration risks, higher thermal water temperatures that are naturally associated with power projects are more likely to produce scaling and cause more damage to below and above ground facilities than lower temperature thermal waters that are sufficient for heat production. Observed seismicity occurred for both power and heat projects, mainly at the reinjection well locations. Overall eight seismic events with magnitudes higher than ML = 2 have been observed at three locations thus far, ranging from 2,0 to 2,5. Power projects are more ambitious than heat projects and awareness should be raised for the associated uncertainties. However, as power production from geothermal resources remains an important pillar for any energy conversion scenario, significant improvements in all associated technological sectors need to be made in order to reduce the uncertainties described in this paper.

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