A system for real-time management and optimisation of industrial utilities facilities is presented. The system, given the demand from the process (steam of various levels, power), optimally allocates the load to the available utilities equipment (boilers, turbines, etc.) and external sources (national power grid). The utilities plant is considered to consist of three interacting sub-systems : fuel, power, water. The system is based on a modelling framework where operational characteristics of the utilities equipment are decomposed from nominal design, so that the computational efficiency is increased without loss in rigor. Discontinuities are removed with the introduction of appropriate transition functions and the complete problem is formulated in a non-linear programming framework. An industrial scale benchmark problem is used to test the approach. The tests demonstrate the efficiency and robustness of the system.