During the last decade, the importance of process development has persuaded researchers to propose a great number of optimization models on "production planning" and "production scheduling" for different productive processes. Although many scheduling and planning models are proposed in the past decade, there are few models that handle various applicable goals. In this paper the main objective is developing and extending the traditional scheduling formulations to accommodate optimization of utility (especially energy barriers) demands and supplies. In the context of optimization, the final formulation takes the form of a mixed-integer programming. For this purpose a mathematical model is proposed on the basis of continuous-time representation and applied to two examples to present its effectiveness. (c) 2006 Elsevier B.V. All rights reserved.