Today, the supply of electricity still comes mainly from large power plants fueled primarily by fossil fuels that operate through established distribution and transmission systems. Although these systems provide an efficient service worldwide for many years, times are changing. Modern societies have understood that in order to mitigate climate change, it is needed to reduce polluting emissions. The optimum use of traditional sources must be accompanied by an ever-increasing use of renewable energy sources (RES). There is therefore the spread of a wide range of energy sources that involve a number of complexities in terms of improvements in RES’ technologies and design of electrical networks. The EU has launched several initiatives to increase the use of RES in all EU countries. With the climate and energy package, energy policy becomes a unilateral commitment in Europe. The achievement of macro-objectives outlined in the package is entrusted to the synergistic effects of different proposals closely linked. With regard to the RES Directive 2009/28/EC on the promotion of the use of energy from RES, it sets the overall policy framework in order to ensure coverage of 20 % of the energy demand of the EU through RES to the electricity, transport (biofuels), and heating–cooling sectors. The objectives of mandatory coverage with RES are implemented at the national level and they vary from one country to another; they are between 10 and 49 % of final consumption by 2020.