the total electric power increase of the Unit by up to 24.5 MWe for the analyzed operational conditions supported by the measured data. The reduction of the steam extraction also leads to the reduction of the heat regeneration within the Rankine cycle and the decrease of the steam turbine plant efficiency, but this effect has a smaller influence on the Unit gross efficiency than the increase of the steam boiler efficiency due to the recovery of the waste heat in the additional economizer from the exit flue gas. In total, the important increase of the Unit gross efficiency is achieved. These changes of efficiencies depend on the feedwater flow through the additional economizer. The maximum increase of the Unit gross efficiency by 0.53 percentage points is achieved for the feedwater mass flow rate through the additional economizer in the range from 33% to 38% of the total feedwater mass flow rate to the evaporator section of the steam boiler. In the same range of the feedwater flow through the additional economizer, up to 9.4 MWe of the Unit electric power is produced on account of the exit flue gas utilization, where 0.4 MWe is obtained due to the reduction of the pressure drop along the parallel feedwater pipelines and the economizers sections and consequent reduction of the main feed- water pump power. The exit flue gas temperature after the Ljung- strom air preheater is reduced by 28 C, but this temperature is still higher than the temperature of the sulfuric acid dew point and there is no risk for the low temperature corrosion in the electro- static precipitator. The additional feature of the performed solution is the possibility to control the steam turbine power by the change of the feedwater flow through the additional economizer, while the parameters and the mass flow rate of the fresh steam are being kept constant in front of the high pressure section of the steam turbine. The economic analysis shows that the project is extremely attrac- tive. For the electricity price in the range from 50 euros/MWe to 100 euros/MWe the internal rate of return varies from 58% to 115%, while the simple pay back period is in the range from 22 months to 11 months respectively.