There is a tremendous potential to improve performance of geothermal applications in Turkey. Exergy analysis is proven to be a powerful tool in performance analysis of geothermal applications. Geothermal energy assisted processes can be improved and optimized dependent upon exergy analysis. In this study, a thermodynamic analysis is presented for optimizing and describing the effective working conditions for geothermal power generation systems (GPGS) in Turkey. For this purpose, an exergy-based approach is performed for simple organic Rankine cycle (ORC). The variations of the parameters that affect the system performance such as working fluid, evaporation temperature, condenser temperature, mass flow rate, and dead state conditions are examined. First and second law efficiencies, total irreversibility, and economical profit based on network output of turbine are calculated for geothermal power generation systems. The results of the analysis show that the first and second law efficiencies decrease with decreasing of evaporation temperature. Similarly, total irreversibility increases while the second law efficiency and economical profit decreases as the condenser temperature increases.