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.