Cool roofs are an inexpensive method to save energy and to improve the comfort level in buildings in mild and hot climates. A high scale implementation of cool roofs in Andalusia, in the south of Spain, could potentially save 295,000 kWh per year, considering only residential buildings with flat roofs using electrical heating. At the current energy prices, consumers can save 59 million euros annually in electricity costs and the emission of 136,000 metric tons of CO2 can be directly avoided every year from the production of that electricity. If radiative forcings are considered, Andalucía can potentially offset between 9.44 and 12 Mt of CO2. All the provinces in the rest of Spain are also studied in this paper. The biggest savings are achieved in Gran Canaria (48%), Tenerife (48%), Cádiz (36%), Murcia (33%), Huelva (30%), Málaga (29%), Almería (29%) and Sevilla (28%), where savings are greater than 2 euros per square meter of flat roof for old buildings with dark roofs. For the biggest cities the range of savings obtained are: between 7.4% and 11% in Madrid, between 12% and 18% in Barcelona and between 14% and 20% in Valencia. ► We estimate potential savings in energy, CO2, and money for cool roofs in Spain (residential sector with flat roofs). ► Average savings are of around one euro per square meter in the biggest cities. ► Potential savings are of more than 2 €/m2 in the hottest cities. ► In Andalusia the potential savings are 300 MWh, 60 millions euro and 136,000 tons of CO2 per year. ► With forcings, the CO2 equivalence of cool roofs in Andalusia is between 9 and 12 Mt.