To increase the energy efficiency of coal flaring, a technology with mechanochemical activation of coal by the mills is being developed at the Institute of Thermophysics SB RAS. The technology is aimed at increasing coal reactivity and can be used to replace high-reactive expensive and difficult-to-obtain fuel oil for ignition and lighting of pulverized coal boilers of thermal power plants (TPP) using mechanically activated microground coal. A technique for assessing the technical and economic efficiency of using the technology of mechanically activated microground coal is suggested. The investment attractiveness of replacing fuel oil ignition and lighting with mechanically activated microground coal on a number of pulverized coal boilers of thermal power plants of Siberia is presented.