Hello Ray.
We have had solar hot water for 7 years. The make is SolaHart.
It is made in Australia. I suppose there are spanish equivalents.
The panel and tank sit on the roof. The water is gravity fed.
It provides all the hot water we need most of the year. Perhaps a few times in winter after a sequence of dull days, we need to use the immersion heater which is built into the tank.
I believe it is now a law in spain that all new builds must have solar hot water heating.
It has saved me a lot of money. I think the pay back is in the order of 5 years but that depends on how much you use it etc. Money well spent in my view.