The objective of this thesis is the optimal operation of a complex energy system via the \Rolling Horizon" algorithm (also known as \Receding Horizon" or \Model Predictive Control"). The target of the optimization will be achieving the lowest possible monetary expense given a pre-determined energy demand (heating, cooling and electric power), by determining the optimal mix of power production from the components of a HRES system, including the option of buying or selling energy to the national grid. The energy system will also be subjected to uncertainty in the energy demand forecast, which is going to be managed thanks to the Rolling Horizon algorithm.