The use of renewable energy sources (RES) remains a key element for the future of the planet. Similarly, hybrid energy systems that combine the advantages of clean energy from RES, with diesel generators and battery for storage ensure reliability at times when different forms of RES are not available, are particularly appealing for electricity generation in remote areas. For this, it is particularly important to size effectively the different system components and control strategies, in order to increase efficiency and make it not only reliable, but also economically operational. In this framework, a simulator of a hybrid system combining wind-turbine, photovoltaic and diesel generator system with a battery pack has been constructed, to test this facility and study its behaviour. The hybrid system facility, which is unique in Europe, combines a software and hybrid simulator, for long-term analysis of the system behaviour. The tests included different configurations of the system with various control strategies for fuel savings, which were found to vary the systems efficiency widely. To aim for efficient hybrid systems, and achieve effective co-operation between the different renewable energy systems with more conventional sources, it is critical to understand the interactions between the different systems employed, in combination with the load distribution. This can make hybrid systems more competitive, targeting market penetration in the near future.