Written with people moving from Turkey in mind. The Portuguese rules still apply more broadly.
The Energy Certificate
Every property listed for rent or sale in Portugal must have a valid Energy Certificate. It rates the home's efficiency from A+ (best) to F (worst). This document is mandatory for signing a rental contract.
Tenants should pay close attention to this rating. An "F" rated apartment might look cheap to rent, but it will be freezing in winter and expensive to heat, costing you much more in electricity bills.