In Portugal, the Energy Certificate is mandatory by law, applying to all properties, regardless of whether they are being sold or rented. An Energy Efficiency Certificate (EEC) is an official document that rates a property's energy performance based on its consumption and environmental impact. It helps homeowners, buyers, and tenants understand a building’s efficiency, promoting sustainable living and reducing energy costs. Many countries require an EEC for property sales or rentals, ensuring transparency in energy performance. Improving insulation, using energy-efficient appliances, and adopting renewable energy sources can enhance a property's rating. An EEC not only contributes to lower utility bills but also supports environmental conservation by reducing carbon footprints and promoting sustainable energy use.