The thermal-economic optimization of a combined cycle power plant (CCPP) which can provide 140 MW of electrical power is discussed in this paper. The CCPP is composed of a gas turbine cycle (including, air compressor, combustion chamber, gas turbine), heat recovery steam generator (HRSG), steam turbine, condenser system, and a pump. The design parameters of such a plant are compressor pressure ratio (r_AC), compressor isentropic efficiency (η_AC) gas turbine isentropic efficiency (η_GT), and turbine inlet temperature (T₃), pinch difference temperature (ΔT_pinch), steam turbine inlet temperature (T_a), steam turbine isentropic efficiency (η_ST), and pump isentropic efficiency (η_PUMP). The objective function was the total cost of the plant in terms of dollar per second, including sum of the operating cost related to the fuel consumption, and the capital investment for equipment purchase and maintenance costs …