The article considers existing approaches to assessing efficiency of innovative activity. The paper provides classification of methods for assessing efficiency of enterprises' innovative activity, identifying their merits and demerits. The authors analyzed efficiency indicators from the position of investment efficiency, depending on the type of effects, and indicators applied at various stages of introducing innovations. The article shows multidimensionality of assessing efficiency of innovative activity at enterprises of power industry. It means that except for indicators characterizing the economic effect of investments into the innovative activity, it is necessary to estimate the extent of achieving activity objectives in scientific and technological, social, environmental and other spheres; to combine quantitative and qualitative standards; to consider purposes of all participants of the innovative activity. The article validates the necessity to apply expert estimates and presents the technique of assessing the innovative activity of the enterprise on the basis of expert methods, which, in combination with the existing assessment methods, allows enterprises – interested parties – to consider similar data, comparing the innovative activity of the enterprise to the one of other enterprises, estimating advantages and disadvantages of their own resource base, proving thereby the effective cooperation. The authors validate the necessity to calculate the efficiency of the innovative activity through the complex assessment that considers interests of the interested parties – enterprises of power industry. In order to ensure effective management of the innovative activity at enterprises of power industry, it is necessary to consider specific features of power industry and to estimate the external factors that influence efficiency. The paper provides the model presented in the form of the network structure and using methods of a multicriteria choice of decisions. This model helps to solve the problem of selecting the most effective innovative project from positions of different subjects involved in the innovative process. There is formulated the generalizing indicator of assessing the innovative project efficiency in the power industry of the region.