Influence of utility prices on the optimum process structure was studied. Different prices of utilities and increasing investment costs (inflation) over three different decades have been considered. In one decade the fuel price was very low while in another one it was very high. Process structures in these decades were derived using pinch and nonlinear programming methods on a hydrodealkylation of toluene process with diphenyl recycled. The results showed that structures differed in the three decades because of different prices and for that reason a common process configuration, usable both for eventual future high or low fuel prices, could be developed.