The behaviour of the generation-consumption system with an energy storage facility is examined. Such a system is simulated using the operations research method. The aim is to simulate the operation of the system week by week for a period of one or more years. The simulation represents optimisation of production costs. The advantage of the model is that it is possible to assess the influence of such varied parameters as the storage capacity, generating capacity, importation costs on the behaviour of the generation-consumption-storage system. It also makes it possible to study the various potential ways of optimising the operation of the system over a period of one or more years