A computational model of a combined cycle power generation unit is developed and applied to one operated by a local utility company. The objective is to predict the performance of this unit by carrying out energy and exergy analyses of its components. The model is based on thermodynamic, heat transfer and psychrometric principles, and includes an inlet air conditioning (fogging) system for the gas turbine cycle. To evaluate the model, simulation results are compared with available plant test data at rated load with and without the inlet fogging system in operation.