Our solar water tubes have been heating our hot water for over three years now after an excellent installation from John Adams. Apparently there are over 90,000 of these installed in the UK now and quite a few in the Wedmore area. They are an excellent way of reducing the environmental impact of your house and involve virtually no maintenance. They can heat your hot water even in mid winter on a very sunny day but it will be working the hardest between April and September.
Sadly there are precious few grants available for the installation of the tubes, approx. £400. Payback is difficult to calculate since it depends on how you usually heat your hot water; gas, oil, wood, or electric as well as whether you installed the kit yourself (approx £1500 or by a registered installer approx £3000) and how much hot water you get through. For us I reckon it will take about 8 years to see the payback.
What will shorten this payback time is a new scheme called the Renewable Heat Initiative from Good Energy who will pay you for the hot water you produce, as far as I know, the first such scheme. This should pay us about £85 per year which will considerably shorten the payback period.
Of course in the meantime, our energy bills are reduced which during such difficult times helps us sleep sounder.
What I am trying to emphasise here is that solar thermal is becoming mainstream even in the UK. The payback is shorter with schemes from the likes of Good Energy and the only hurdles are the lack of a south facing roof and conservation officers if you live in the village centre!