Abstract: An energy management system uses an expert engine and a numerical solver to determine an optimal manner of using and controlling the various energy consumption, producing and storage equipment in a plant/communities in order to for example reduce energy costs within the plant, and is especially applicable to plants that require or that are capable of using and/or producing different types of energy at different times. The energy management system operates the various energy manufacturing and energy usage components of the plant to minimize the cost of energy over time, or at various different times, while still meeting certain constraints or requirements within the operational system, such as producing a certain amount of heat or cooling, a certain power level, a certain level of production, etc.