Most industrial sites satisfy their heat and power needs through utility plants, which convert basic energy/water feeds into steam, electricity and rotational power. These systems offer the opportunity for substantial savings given their large investment requirements and operating costs. However, minimising such expenditure also represents a very challenging task due to the large number of design choices and methodology for the design and operation of utility plants, which fully exploits their inherent flexibility when they are subject to variable conditions (e.g. demands, prices, ambient temperature). The suggested MILP formulation allows structural and operational parameters to be optimised simultaneously and the procedure is robust enough to tackle real industry problems. © 2005 Elsevier B.V. All rights reserved.