On Mon, 19 Jan 2015 16:57:51 +0000 (UTC), Andrew Gabriel wrote:

Maybe but when the time switch on the CH/HW (open vented cylinder)
failed I took a while fixing it, then noticed that the gas bill
had
dropped so didn't bother until I moved out. The cylinder would
only
take 20 mins to reheat and would stay hot enough for washing hands
and dishes for the best part of 48 hours. Running the system under
"on demand" rather than a time switch certainly saved money.

Yes, of course, but the idea of waiting 20 mins before you can have
a shower will not be acceptable to many people.

Some people must have a very poor abilty to think/plan ahead... Bear
in mind that 20 mins was to 60 C plus from 20 ish. It would be hot
enough for a shower in not much over 10 minutes. Get up, turn on HW,
make coffee. have a slurp, 10 mins gone easy.

When you've finished, there's still hot water left which might get
wasted if you aren't around to shower for a few more days.

No other washing? Be that just hands or the dishes?

If you only heat a cylinder on demand, then a combi is probably cheaper
to run for you (and more convenient, being instant).

I reckon it would be quite close with a well insulated tank and
normal HW use for hands dishes etc.

--
Cheers
Dave.