Thermoeconomics is the branch of engineering that combines exergy analysis and economic principles to provide The system designer or operator with information not available through conventional energy analysis and economic evaluations but very important to the design and the operation on cost-efficiency of a system. Introducing the process computer we can know in every moment the price of our product, in this case the price of the steam with the desired quality. In this paper is presented a mathematical model to count a kilogram of steam in order to optimize the exergetic efficiency of a steam boiler
