So I actually have experience with these in the north of Sweden - they are definitely more efficient in summer, but do provide some amount of hot water as well in winter on days with clear sky (of which there are few).

On the topic of using this for heating in the Mediterranean - I don't think that's where you want to invest, installing underfloor heating in one of those houses. That will cost some serious money. It's probably wiser to spend it making the home less prone to get cold/hot using insulation in that case. I will admit to being out of my depth when it comes to optimizing buildings for hot climates though