An original methodology for the analysis of systems and processes is developed. The methodology is based on the quantities exergy, cost, energy and mass, and is referred to as EXCEM analysis. The development of a code for EXCEM analysis by enhancing Aspen Plus, a state of the art process simulation code, is described. Applications of the methodology and code to the analysis of several engineering processes (production of electricity, hydrogen and hydrogen derived fuels) are discussed. The relations between exergy loss and capital cost and those between exergy and environmental impact are investigated. EXCEM analysis may prove useful to investigators in engineering and other disciplines.