The paper considers methods of identifying the qualitative properties of energy technology objects in terms of equivalence and order, their classification by alternative attributes and determining the number of objects of equivalent classes of non-metric scales. It is found that the control of energy processes of a thermal power plant is carried out through certain qualitative properties that characterise coal and its products by size, and thermodynamic production processes, such as transportation and heat conversion by determining the lost heat of each process, which are revealed in the equivalence relation and classified into two equivalent classes, forming the corresponding name scales. The frequencies of occurrence of names, objects of equivalence classes of non-metric scales of R5 coal lumps/ R90 particles of coal dust, ash, fly ash, and heat of burnt fuel in the processes of production, transportation and conversion, and in general, the heat used by a power unit, which are important technological, technical, economic and environmental indicators of a power unit, are analysed. It is proposed to use such relations as the frequency of an event, equal to the ratio of the number of observations of this event to the total number of observed single events, for qualimetric assessment by non-metric scales, which coincides with the definition of the frequency of an event in the theory of probability and encourages the involvement of such relatively new entities as an event, its frequency and probability in the theory of scales.