In last years, the energy efficiency in non-interconnected islands became an important topic, since the electricity production is often based on diesel generators, thus contributing to the global warming. Italian government recently emitted two decrees to promote the introduction of renewable energy technologies in 21 non-interconnected islands, both for electrical and thermal uses. In this paper, the economic and environmental feasibility of the introduction of renewable energies in the island of Pantelleria was assessed adopting an optimization approach. Furthermore, the flexibility provided from the local desalination plant and the domestic water heaters was evaluated. The final demands for electricity, air conditioning, domestic hot water and freshwater were analyzed, and the island was schematized as a multi-carrier energy hub and optimized through a mixed integer linear programming algorithm. Results prove that the renewable energies may provide a strong reduction of operating costs and greenhouse emissions of diesel generators in non-interconnected islands, although the optimal configurations differ according to the objective function of the optimization.