Since June 2013, the energy efficiency certificate is mandatory to sell or rent any property, according to Royal Decree 235/2013. This Royal Decree approves the basic procedure for the energy certification of buildings, both new and existing. It is important to know that in addition to having an energy efficiency certificate, it must be registered with the competent body of the Autonomous Community. The energy certificate is valid for five years, from the day it is registered in the Competent Body of each Autonomous Community. When an apartment, which has an energy efficiency certificate in force, undergoes works that affect the envelope or the system, the certificate must be updated in case you are going to sell or rent the property.