The solution to the problem of energy saving and improving environmental security can be provided only by a systematic approach, which should be based on the analysis of the efficiency and environmental friendliness of energy production. A methodology was developed and implemented to assess the qualitative state of operation of specific thermal power facilities by energy and environmental characteristics in real time, taking into account the set of energy, environmental, passport and normalized performance of its units, facilities and devices. The methodology in practice allows in a complex to determine simultaneously the level of energy efficiency and environmental safety with an assessment of compliance with the level of permissible values for concentrations of pollutants and hazardous substances of the working area and their hazard class. In this case, indicators and parameters of monitoring of various processes of each individual element and component of the energy production facility as a whole, which uses as a source of energy organic fuel, are used. According to this methodology of comprehensive energy-environmental assessment of operating conditions of energy facilities can be compared different in design, thermal, environmental and other scale characteristics of thermal energy cycles, facilities, installations, units and other thermal energy equipment and optimize the choice of energy source for heat and energy production under different schemes of layout of units within the cycles. Application of the methodology of assessment of energy-ecological efficiency of thermal energy processes allows to assess the energy-ecological feasibility of modernization or reconstruction of facilities in order to achieve the best performance of their operation in the heat and energy supply systems of various sectors of the country's economy. The use of the method is demonstrated by the example of calculating the coefficient of energy and environmental efficiency for energy boilers of different capacities.