The present study analyses the land-use changes associated with solar power plants in the Alentejo Region of Portugal. The adopted method is based on the use of GIS to overlay land use and occupation data with the areas of solar plants installed in recent years. The results are compared with the case of the Andalusia Region in southern Spain, where a similar study has already been conducted. This comparison reveals the pattern of expansion of these technologies in this area of the Iberian Peninsula. Public policies and land use planning should be reconsidered to direct the development of these technologies according to rules that facilitate the establishment of decentralised models, avoiding implementing large plants and preventing irreversible impacts on land use, landscape, and biodiversity.