To remain competitive on the international market companies have to improve the energy system of their chemical production sites. Many consultants who work in this field have developed appropiate methods and application programs to fulfill this task. The latest development is a procedure called SitEModelling(TM) which covers the thorough experience of experSCience. This paper describes the SitEModelling(TM)-procedure and the corresponding program. Case studies are included to present application and value of the program.