Domestic heating and cooling is responsible for a fair percentage of world energy consumption. Heat pumps offer the most energy efficient way to provide heating and cooling in many applications, as they can use renewable heat sources of the building＇s surroundings. A number of related heat pump technology versions exist that have led to significantly lower heating and cooling energy consumption in certain climatic conditions. In this paper, a comparative discussion is giver. of the effect of climatic conditions on applying ground source heat pump technologies. Specific examples are given for northern and southern parts of Europe. It is shown that the attainable building energy consumption reduction with ground source heat pump systems may be significantly higher in the warmer Mediterranean climatic conditions. To this end, advanced technology residential heat pump systems should be employed and their operation matched to the specific climatic conditions. It is concluded that climatic conditions significantly affect the performance of heat pump systems, which should lead to markedly different strategies for domestic heating and cooling, if an optimization is sought on sustainability grounds.