In this paper, we present the development and automated implementation of an iterative methodology for exergoeconomic improvement of thermal systems integrated with a process applicable to real, complex plants. The methodology combines recent available exergoeconomic technique with new qualitative and quantitative criteria for the following tasks: (i) identification of decision variables that affect system total cost and exergetic efficiency; (ii) hierarchical classification of components; (iii) identification of predominant terms in the component total cost; and (iv) choice of main decision variables in the iterative process. To show the strengths and potential advantages of the proposed methodology, it is here applied to the benchmark CGAM cogeneration system. The results obtained are presented and discussed in detail and are compared to those reached using a mathematical optimization procedure. (C) 2003 Elsevier Ltd. All rights reserved.