The rising costs of oil and its derivatives and the increased sensitivity of public opinion, led to the ratification of relevant international treaties on the reduction of carbon dioxide emissions into the atmosphere (Kyoto Protocol 2020). This has meant that the industry has become one of the first major users of systems to heat pump to replace all those applications in which hot water is required at temperatures up to 60-70 °C. This new trend, combined with massive use of electricity from renewable sources (solar photovoltaic), has brought a drastic reduction in the cost of electricity resulting in an additional economic benefit .