The expected rapid rise in power demand during the 21st century is accompanied by mounting problems with power plant sitting, environmental impact, resource shortages, and increasing shortage of available space for fuel and power generation and distribution. With growth of modern technologies into the world households, it is necessary to replace clean energy, reduce irreversibility in consumed energy systems and optimize the energy consumption. In this regard technical and economical analysis of any thermal systems is very necessary. It is increasingly recognized that for any conceptual design, analysis and development it is necessary to add the subject of exergy (a second law of thermodynamic) to the conventional energy analysis. Unfortunately this part of exergy is not included in the teaching of thermodynamic of our universities. In macroeconomics, exergy offers a way to reduce resource depletion and environmental destruction by such means as an exergy tax. By minimizing life cycle cost, we find the ‘‘best’’ system under given prevailing economic conditions, and by minimizing exergy losses, we also minimize environmental effects. Exergetic production cost (EPC) is a new method developed for the analysis and optimal improvement design of combined heat and power (CHP) systems. In this study EPC scheme is applied for the Shiraz solar power plant to find the effect of amortization and starting temperature on the electricity cost. Another example for a chemical plant is also analyzed by EPC method to minimize exergy cost. This study is useful for the students as well as engineers who are involved in the process design and energy saving subjects.