The optimization of design and operation of trigeneration plants for civil applications is a very complex task, because of the large number of internal and external variables affecting the energetic and economic results that may be achieved. Further, energy-saving and profit-oriented optimization processes usually lead to different solutions, in terms of plant lay-out, optimal size of components and operation strategy. Thermoeconomic methodologies are very effective theoretical structures for the optimization of industrial energy-systems characterised by regular energy-demand profiles; however, they are hard to use when approaching civil applications and energy systems in unsteady operating-conditions. In this paper, the potential of thermoeconomics for the analysis of CHCP applications in buildings is explored; two main procedures to address the problem are presented, a simplified design optimization and a detailed integrated optimization of plant lay-out and operation. The former approach, based on the use of aggregate consumption data, is described more in detail and finally applied to a trigeneration plant serving a 300-bed hospital, situated in a Mediterranean area; the results are finally compared with those available in the literature and determined by using demand cumulative curves or numerical methods. (c) 2007 Elsevier Ltd. All rights reserved.