Abstract: The operating characteristics of thermal power units have changed after they have undertaken large-scale thermal loads,and coal consumption evaluation has become more complicated. The current coal consumption calculation methods for power generation cannot reasonably evaluate the real coal consumption level and actual coal saving effects of thermal power units.Based on the actual production process of the cogeneration unit,the calculation method of the coal consumption rate of the back pressure heating unit is redefines.Combining with the coal consumption rate of the back pressure unit and the pure condensing unit,the parallel steam flow theory is used to calculate the coal consumption rate of the condensing bleeder turbine unit,and the social coal saving index is proposed to objectively evaluate the energy saving point and energy saving of the cogeneration unit.The calculation example results show that the new coal consumption index can accurately reflect the coal consumption level of power generation process and the social energy saving effect.