Just taking this as an example, a DIY kit, with a simple plumbing
arrangement (for those of us with tanks!), with an additional pv
panel to
drive the pump, is =A31900.

Excessively expensive. Doesnt have a hope in hell of paying back.

Solar heating can payback very well indeed, but only if you design it
right. I have never seen a commerical system that I would describe as
desgiedn right.

For some odd reason, most solar engineers live in a world where cost
and payback are complete non issues. This problem has dogged solar
energy all along.

There is a good ng for this, alt.solar thermal.

Solar HW is quite tough to make pay; it can be done, but most systems
dont achieve it.

Solar flat panel space heating OTOH captures vastly more heat, costs
less to install, is simple to blue peter, and has excellant payback
figures as long as you design it sensibly, which is easy compared to
DHW heating.

Theres another good payer: a crossflow heat exchanger on the shower.
Warm water going down the drain heats the cold supply to the shower,
result is you use much less hot water. Payback can be under a year,
depends on level of use.


NT