In message , John Beardmore
writes
) 70% of hot water, not central heating or gas for cooking, it's
patently impossible for it to be viable

Yes, though pay back time is not the only reason people invest in
things.

What's the pay back time on a new car or a new kitchen ?

No idea in your circumstances, but it is less well defined than solar

Solar panels have a reasonably well spec'd return


I don't see what my folks signed for as being economically viable

--
geoff