The energy certificate is essential in order to sell or rent a property; its function is to provide us with information on consumption and CO2 emissions. It has been compulsory in Spain since 1 June 2013 in order to rent or sell a property or premises. The obligation to show the certificate is regulated by Royal Decree 235/2013 and the responsibility for obtaining the certificate lies with the owner of the property, who must contract the services of a certifying technician to obtain it.