Exergy analysis is a relatively new part of thermodynamics. It uses the concept of exergy for studying technical processes. This method is widely used for analyzing refrigerating plants and various cryogenic systems. It is convenient because the character of processes in the system analyzed are of no principal meaning. In some new systems there is no thermodynamic cycle altogether (thermal elements). Increasingly growing is the meaning of the basic quality of this method, its universality. Furthermore other efficiency indices do not depict reality of processes, e.g. adiabatic COP compares the real process with an adiabatic, i.e. theoretical one, which does not take place in the machine. Unlike those indices exergy COP compares two characteristics.