In this work a thermodynamic model of a steam turbine power plant that is part of a combined cycle power plant was made. In order to find the best configuration of the heat exchangers inside the multi pressure heat recovery steam generator, heat exchangers network was made. In the heat exchangers network each pressure level of steam as well as steam superheating is presented with one separate column in the heat exchangers network. It allowed the arbitrary configuration of the heat exchangers within the multi pressure heat recovery steam generator. Optimization routine determines the enthalpy increment within each heat exchanger as well as pressure and steam mass flow for each pressure level. In the case of thermodynamic optimization, objective function is represented by the maximum thermodynamic efficiency, but in the case of thermoeconomic optimization objective function is made of minimal thermoeconomic losses in the steam turbine plant. Genetic algorithms were used as a robust method of finding an extreme of the objective function. In comparison to previous scientific research, it is shown that there are better configurations of the multi pressure heat recovery steam generator, mainly in the form of parallel position of heat exchangers of different pressure levels. Thermodynamic and thermoeconomic optimization showed that the best plant is the one with three steam pressure levels with superheating.