The paper presents the results of the thermodynamic model of the GE LM6000-PF gas turbine with a water heat recovery boiler. The maximum electrical power output of the unit is 48 MWe. The turbine is a part of the cogeneration heat and power plant (CHP). The model was developed in the Ebsilon Professional software. The efficiency of the gas turbine and the output power strictly depend on operating conditions, such as the thermophysical parameters of the inlet airflow. To control the unit operation as well as during the conceptual analyses, the detailed thermodynamic models are increasingly used. Simulations are particularly applicable to the ongoing optimization of the CHP plant operation through short-term planning of energy production, where hourly production parameters are needed to be forecasted on a day-ahead time horizon. The method of the production parameters calculation (electric power, heat output, fuel consumption, exhaust gas composition) was discussed. The procedure for validating the model using the correction coefficients determined based on the real data was presented. The outcome of the model in the form of hourly gas turbine parameters was presented and compared with real ones coming from measurement data from several months of operation. The results accuracy obtained thanks to the developed model is significantly increased when the correction factors are implemented. The mean percentage error of the model was approximately 1%, 3%, and 1.6% for electric power, heat output, fuel mass flow, respectively.