Issues of efficiency of the energy objects (power plants) have been examined. Methodology of exergic analysis of the energy objects’ life cycles has been developed. In the frame of the methodology the concept of life cycle has been defined and dependences for definition of exergy’s cost and electricity generated during the life cycle of the energy of an object have been given and substantiated, as well as measure of efficiency has been formulated. By using this methodology definition, comparison and analysis of energy efficiency of various energy facilities could be quickly produced.