From April 2008 onwards, it is mandatory to inform the consumer of the source of the energy sold by the retailer and its associated environmental impact on electricity bills and marketing communications. This information is shown in graphs and labels that are the same for all the power companies, as established by the Spanish National Commission for Markets and Competition (CNMC)

In order to prepare these labels and graphs, the CNMC has set up a Guarantee of Origin system that enables the origin of the energy supplied by the various companies to be determined. The mix of energy sources of each supplier for 2017 has been calculated and published based on the mix of primary energy sources that have been used in electricity production for 2017, and the Source Guarantees of each retailer.

During 2017, 36% of the energy sold by Iberdrola has been certified as being of renewable origin. As regards CO2 emissions and radioactive waste, Iberdrola Clientes has been labelled C in both cases, compared to double D for the national average.

Iberdrola thus confirms its firm commitment to renewable energy sources and its position as the world leader in the production of wind power.