The utilization of deep geothermal resources for combined heat and power generation in Germany has increased slowly but continuously during the last years. Due to the growing technical readiness, the focus is now shifting from the first proof of concepts to optimizing the performance of existing plants. One promising approach is the further development of the monitoring software of geothermal plants. While the current software enables a safe operation of the plant, it does not offer any profound features regarding documentation, data validation, condition monitoring and enhanced maintenance strategies. Due to this so far unexploited potential, an improved novel software is developed within the project Monitoring by the Geothermal-Alliance Bavaria. This thesis is carried out as part of this project and aims to provide specific recommendations concerning the features and methodology of the software. In order to achieve these goals, real operating data of two geothermal plants for combined power and heat production are assessed. Resting upon the evaluation of more than 4,000 entries of the documentation system of one reference plant, a detailed assessment concerning the reliability of the plant and its main weaknesses is derived. On this basis, an advanced system for the future documentation of incident data is developed to remedy the identified limitations of the current system. An enhanced validation strategy based on the VDI 2048 guideline may significantly improve the interpretation of the process parameters’ accuracy. For instance, currently the thermal water flow rate, which is a crucial parameter for the process evaluation, cannot be measured reliably. However, the actual flow rate may be estimated accurately by implementing a validation algorithm, which assesses the heat balances for the heat exchangers. By utilizing suitable key performance indicators (KPIs) within the future software, an improved condition monitoring may be achieved. To select these KPIs, various parameters are evaluated with respect to their potential benefits. Regarding the condition monitoring, systematic parameters, such as the thermal efficiency, exhibit the difficulty of being strongly sensitive to the ambient temperature. Therefore, the actual systematic parameter should be compared to a value indicating the optimal achievable performance for the current ambient temperature and flow rate. With the dimensionless resistance factor and the systematic pump efficiency, two suitable component specific KPIs are identified for the condition monitoring of thermal water pumps and heat exchangers. However, a comparable condition monitoring of the turbine and condenser is only to a limited extend possible. In addition, the investigation of the degradation processes of the thermal water pump reveals a significant improvement potential by adapting the acidification interval to the characteristic of the performance change of the pump. Currently, acidification are carried out in an interval of six to eight months. Within this period, the thermal water flow rate reduces up to 28%, which results in significant revenue losses. The evaluation reveals that despite the additional costs for the acidification, the increases in the achievable flow rate due to shorter acidification intervals may result in a financial benefit of more than 100,000€ within a period of eight months. Finally, a general strategy for the implementation of an enhance maintenance strategy concerning the optimal acidification is elaborated.