One of the important tasks for optimal design and analyses of site utility systems is targeting total annualized cost and cogeneration potential. This paper introduced a new cogeneration and total annualized cost (TAC) targeting models that were developed to estimate the cogeneration potential of site utility systems and total annualized cost. The procedure which was proposed here provided a consistent, general procedure for determining mass flowrates and efficiencies of the applied turbines. This algorithm utilized the relationship of the entropy with the enthalpy and the isentropic efficiency. It is considered superior to previous works in that it was accurate, did not require any cumbersome simulation for initiation and could be easily traced,which enhance its programmability, considering full lifetime of the utility prices and it can estimate TAC and TASP with diffrent cost functions. Also, the developed model based on the trends of historical prices has been considered for estimation of utility costs. In addition, developed graphical representations based on site utility grand composite curve (SUGCC) were introduced: (1) TAC-SUGCC, to illustrate On the same diagram heat recovery through the steam mains, shaft work production, TAC, temperature of steam mains and steam flow rate simultaneously; and (2) TASP-SUGCC, to demonstrate TASP on the extended SUGCC diagram. Finally, two case studies were used to illustrate the usefulness of the new method. (c) 2012 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.