[permaculture-oceania] Electricity usage of electric hot water heaters

[jedd]

 Howdi,

 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?

 I'm sure it's highly dependent on capacity, ambient temperature,
 phase of the moon etc -- but I'm just as sure that there's a point
 where all that makes no matter.  My gut feel is I'm in that zone.

 Even at full ball, to heat the tank up is going to involve
 (max) 2400W x 1hr.  I don't know if  these things trickle less
 power to maintain a temp, or just jerk savagely between the
 minimum and maximum thermostat settings.

 ~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.

 I believe that the concept of off-peak electricity for hot water
 heaters disappeared a decade or more ago -- which makes calculations
 less complicated.

 taa,
 Jedd.