Geothermal binary power plants can be utilized using low-grade resources. As power plants being thermal conversion units, there is a need to combine economics and exergy optimization from the available energy resource. This study analyzed isobutane air-cooled binary power plants at different geothermal brine temperatures at 187oC, 156oC, and 120oC, accordingly. The geothermal binary power plant was designed and analyzed using Engineering Equation Solver (EES) code and System Advisor Model (SAM). Further, it was optimized by different turbine inlet pressure, and EES results which are the basis to Levelized Cost of Electricity (LCOE) calculations. The exergy efficiencies were obtained between 20-35%. Thermal efficiencies were between 6 - 9.5%, and LCOE varied between 0.079 and 0.099 $/kWh. It is important to combine thermo-economic, exergy, and LCOE in power plant design for optimum utilization of available resource.