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Repowering means addition of gas turbine unit(s) to a steam power plant in order to make use of the exhaust gas heat and to increase efficiency of the new combined cycle. There are two groups of repowering methods: partial repowering and full repowering. Full repowering is more common and is used in power plants with nearly ended useful lifetime. In this case the capital investment is considerably reduced compared with the case of making a similar combined cycle. Objective functions are per kWh electricity cost and exergy efficiency. These functions are based on important independent variables of heat recovery boiler, steam turbines, gas turbine. Finally, considering the introduced objective functions, it is tried to achieve the most optimized techno-economic characteristics for Be'sat power plant repowering cycle, using genetic algorithm optimization method with two scenarios of single and multiobjective.