Energy Saving, Energy Efficiency or Renewable Energy: Which Is Better for the Decarbonization of the Residential Sector in Italy?

The residential sector is currently responsible for approximately 30% of the final energy consumption and 12% of direct CO2 emissions in Italy, mainly due to the heating and cooling of buildings and the use of domestic hot water. Such figures show a significant potential for reducing non-renewable primary energy utilization to comply with the decarbonization constraints of the European Union. In this context, the purpose of this work is to provide a quantitative assessment of the effect of a different number of actions (eight for energy savings, four for energy efficiency and two for the installation of renewable energy plants) that could be implemented at the national level to reduce the consumption of natural gas in the residential sector. Two typical residential buildings are dynamically simulated using Trnsys®, and the savings from energy, economic and CO2 emissions points of view are evaluated in the different climatic zones of Italy. The most effective action foresees the replacement of natural gas boilers and old air conditioners with modern heat pumps and air/air chillers as well as the installation of a controlled mechanical ventilation system with heat recovery. This solution allows for non-renewable primary energy savings of 58% and an economic savings on annual energy costs of 72%.