"Ian Stirling" wrote in message
...
TonyK wrote:
Hi

Just looking for a guide, not actual calcs, from someone who can give an
authoratative "yes" or "no"...

Fitted a 330l pressurised cylinder (insulated) earlier this year and to
date
has been left switched on all the time due to high demand for hot water
literally 24hrs a day. Now demand is dropping off dramatically and will
only
be needed Fri-Sun so...

Should the cylinder be switched off Monday - Fri am allowing the water
to
cool and reheat from what I asume would be almost cold on Friday pm. Or,
is
it more energy efficient to leave it on and let the thormostat regulate
power consumption to keep it up to temp throughout the week?

As others have said, it's best to turn it off.
However, if it's in a place where this is possible, you'll get a
significant
increase in time to cool down if you get a 5 quid roll of loft insulation
and
pack it (loosely, but leaving no air gaps) round the cylinder.


Coincidentally was thinking about the same question only this only this
morning. Would there be any economy in switching the water heater
tank/cylinder off for certain periods, especially since now only one person
(me) living in this house?

Talking to myself driving to technical college, went like this. Self, I
said;

"Normal practice here is to leave the hot water heater, which is typically
30 imperial gallons with upper and lower 3000 watt heaters with individual
thermostats in a flip-flop arrangement, on, all the time".

BTW we went on vacation on one occasion for a couple of weeks and switched
off the hot water circuit breaker; when we returned the tank water was still
tepid! So have always assumed that heat loss to the ambient surroundings in
our unheated average 55 to 60 degrees F. basement, is very small?

" What about temporarily hooking up an electric clock to the heaters. Then
see how long the heaters came on while domestic hot water use was zero, to
maintain the set temperature.
If the clock ran for say ten minutes during a ten hour period.
Then electric consumption would-be 10/60 * 3 = 0.5 Kilowatt hours or units
per 10 idle/quiescent hours. An average of 0.05 units per hour?
Electricity here now costs about 9 cents (Canadian) or roughly 4 pence per
unit all charges, such as sales tax included
Using these hypothetical numbers; then if unit left on for 24 hours, with no
use of domestic hot water, 24 * 0.05 * 0.04 = approximately 5 pence per
day?".

For a two week holiday I would in fact shut off the water pressure and
switch off the hot water heater and, unless mid winter, the electric heat;
otherwise for a quiescent two weeks it might cost, theoretically, about 14
* 5 = 70 pence! Does this make sense or have I slipped a decimal place
somewhere?

Cheers.