The objective of this work is to develop a mathematical. programming model applied to the operational planning of the utility plant of the RECAP Refinery (S (a) over tildeo Paulo, Brazil), as well as its interconnections with the process units. The problem is formulated as a mixed-integer linear programming (MILP) model where the mass and energy balances, the operational status of each unit, and the demand satisfaction are defined in multiple time periods. The model determines the operational configuration of the plant by minimizing utility costs, and identifies steam losses as well as inefficient units by comparing the optimal solutions with the current operation. The MILP is able to accurately represent the topology and optimize the operation of the real-world system under different utility demands and abnormal situations in single and multiperiod scenarios, achieving up to 10% cost reduction. The MILP is currently integrated with the plant database and used for the planning of the refinery utility system. (C) 2007 Elsevier Ltd. All rights reserved.