The aim of the project was to study the potential of borehole systems in Portugal, once its need for acclimatization is increasing. At the same time endogenous and renewable energies are important and necessary to be implemented in the country. The borehole system is a renewable and reliable new technology for heating and/or cooling that has been used in several countries. The potential of borehole systems in Portugal was carried out by evaluating a number of criteria: heating/cooling demand, energy demand, climate, geology, hydrology and population density. The compilation of these criteria resulted in a number of different geographical areas well defined. For all of these areas the EED (Earth and Energy Designer) program was used to calculate the required borehole systems for three different types of buildings. It was concluded that Portugal has moderate to high potential for borehole system applications. The most favorable conditions were found in the north of the country. Borehole systems were increasingly less feasible from the centre to the south and from inland to the coast. The main reasons for this difference was the high cooling demand and the high ground temperatures of the southern areas. At the same time high acclimatization demands gives higher efficiencies for borehole system applications for all the areas of mainland Portugal. / <p>Validerat; 20101217 (root)</p>