I have a house in the Algarve. Years ago I was quoted a figure equivalent to £2,000 for a solar heater with a capacity of 42 litres of hot water. Instead I fitted six long stainless steel pipes of that capacity that connect one to the one above it. They are on the back wall of my roof terrace and cold water enters the lowest one and hot water comes out at the top.
I got the idea when we stopped at the side of a road and I put my hand on some Armco steel rail. It was too hot to hold. The family thought I was crazy until the hot water came out of the system.
At the equivalent of £200 it is very cheap and simple. For most of the year, we take a couple of showers each day. Joined by family April to October the supply is fairly constant all day.
To be more efficient I should paint the pipes a dark colour to aid absorption of the heat. I have not bothered as the water can be very hot now. No sun means having to use gas, but the saving in gas has been enormous and reduced the effort buying and changing bottles.
B. Watts, by email