This paper proposes the use of a site-model to generate marginal values of intermediate materials and utilities. Taking into account the mass and energy balances and interconnections of all production and utility plants, a site-model can accurately calculate marginal values of intermediate materials and utilities by reflecting their actual values on profits. In order to generate marginal values for all required streams by solving the site model, dummy streams with narrow and small bounds are added to and/or taken away from the evaluated streams. The marginal values of adding and taking away a small part of a stream could be different and are strongly affected by where site bottlenecks are located. The locations of site bottlenecks are determined by the capacities of production and utility generation as well as the market values, supply and demand of raw materials, and final products. Examples will be given to illustrate the use of marginal values for debottlenecking a production site as well as assisting business decisions.