Exergetic and thermoeconomic analyses were performed for a 500-MW combined cycle plant. In these analyses, mass and energy conservation laws were applied to each component of the system. Quantitative balances of the exergy and exergetic cost for each component, and for the whole system was carefully considered. The exergoeconomic model, which represented the productive structure of the system considered, was used to visualize the cost formation process and the productive interaction between components. The computer program developed in this study can determine the production costs of power plants; such as gas-and steam-turbines plants and gas-turbine cogeneration plants. The program can be also be used to study plant characteristics, namely, thermodynamic performance and sensitivity to changes in process and/or component design variables.