A systematic procedure is introduced for optimal design and evaluation of cogeneration systems based on the accurate cogeneration targeting model and the development of the R-curve concept through advanced exergetic, exergoeconomic and exergoenvironmental analyses. An advanced exergetic analysis makes this information more accurate and useful and supplies additional information that cannot be provided by the conventional analysis. Moreover, the new graphical representations are proposed based on new concept. Finally, the optimal design of Iran LNG cogeneration plant is performed, in which the usefulness of this method is clearly demonstrated. (C) 2013 Elsevier Ltd. All rights reserved.