I know this has been done to death previously but I am about to visit a friend who is contemplating a *grand design*.
National grid want their usual arm and 3 legs to connect so alternative sources are under consideration. The site is on a steep slope so a basement thermal store would be do-able.
Very roughly, how large a store of water would be required to provide dhw and under floor heating for say 200m2, constructed to something better than current regs.?
The idea would be to heat this with off peak electricity possibly supplemented with power from a PV array. Nice unshaded South facing roof.
I suppose tank life and replaceability is a consideration.
regards