In this master's thesis, the main concern was to calculate the efficiency of a steam power plant with a capacity of 210 MW, which produces steam pressure of 145 bar and 530 °C and includes seven feedwater preheaters, of which two are high-pressure regenerative preheaters, one degasser and four low-pressure regenerative feed water preheater. Default steam power plant has one reheater. Then, the same calculation was performed using the software EBSILON Professional, where a steam power plant, with the same parameters, was modelled and the calculation results, ie obtained total effective efficiency of the steam power plant were compared. Next were observed the dependence of the power plant efficiency on different pressures and the dependence of steam flow on the pressures in the reheater. The main set pressure in the reheater is 38 bar, and later the same calculation was performed with pressures of 25 bar, 30 bar, 35 bar, 40 bar, 45 bar, 50 bar, 55 bar, 60 bar, 65 bar, 70 bar and 80 bar. What was also performed is the thermal calculation of the steam generator, where were shown the emissions of flue gases and in the end it was observed the flue gases purification system from sulfur and nitrogen oxides in Plomin power plant.