[permaculture-oceania] Electricity usage of electric hot waterheaters

[R Freeman]

 Jedd has a hot water system
>  ~200 litres, tall round metal canister, effectively 
> outdoors, ambient  day temps around 20C, night temps around 
> freezing, left unused  for 7-10 days at a time.

And asks
>  At what level of usage do these things warrant being left on?
>  Or rather, at what frequency of *not* being used, does it 
> work  out better to turn them off?

>From personal experience with a very similar setup (and with a family
routine of showering in the evening and putting off doing the breakfast
dishes until after lunch), I found that turning off the HWS at bedtime and
turning it on again sometime the next morning saved significant dollars
(therefore energy). I can't quite remember how much 'significant' was, but I
do recall that it was worth getting up in the night to turn it off if I had
forgotten. Now, in a different rental house I have instant gas HWS. The
house I build will have solar, boosted by a wood fire.

In summary, these things don't warant being left on at all, except during
the time that you are actually using it. 

Setting the thermostat a bit on the low side helps save too, but in that
case more water from the HWS is used and too many people showreing in quick
succession means that the last person has to wait for the HWS to get hot
again or get a cold shower.

--Robert