Abstract Fossil fuel reserves (coal, oil, natural gas, etc.) diminish day by day. In addition, rapid advancement of technology causes an increase in the amount of energy needed. This emerging situation resulted in ever increasing importance of renewable energy sources, and various systems are being developed to utilize these renewable energy sources effectively. In this study, information about Aydin–Salavatli geothermal field’s features and working principles of the 2 power plants (DORA 1 and DORA 2) in the region are given. Power plants’ energy and exergy efficiencies were calculated with the emphasis on the effects of thermal fluids used in power plants. Also, in this study, some correlations were developed. Power plants’ sections which cause exergy losses were identified. Accordingly, improvement suggestions were presented in this study. Additionally, exergoeconomic analyses were conducted while power plants’ investment costs and equipment maintenance costs were taken into consideration.