"Christian McArdle" wrote in message
t...
Depends on the machine. Many take more hot water from the hot draw-off
than
others. Even if a machine only occasionally takes in hot water it is
still
well worth it as electricity is 4 times more expensive. That is a hell
of
a
difference.

Which drops to nothing,

Over a year it is not nothing, it all adds up.

or even negative when the wash
fill is only a few litres, which is
probably greater than the amount of
cold water that is required to be flushed
from the supply line.

If you have a water meter, the cost of
the wasted water may be at least as
significant as the heating costs.

You can have a secondary circulation pump to give instant hot water at the
taps, and cut down on dead leg wastage all around. It is also nicer to have
instant water at the taps.

Yes electricity costs 3 to 4 times as
much. However, the electrically heated
system will be considerably more efficient,
mitigating or even reversing this.

Nonsense.

Some dishwashers can be hot or cold fill.
Best hot, as it is still cheaper
even though the rinse is on hot.

Hot fill dishwashers do not clean
as effectively as cold fill. Hot fill ones
use considerably more energy,
as any rinsing cycles are done with hot water,
rather than cold.

As gas heated water is 1/4 of the price, it is still cheaper.

The supply pipes get hot and cool
down several times in the cycle,

Can be eliminated by using a secondary circulation pump.

leading to much greater parasitic losses.
That is why every single 'A' rated energy
efficiency dishwasher has cold fill.

The A rating is way out of date, as most modern machines now meet it easily
enough. The most efficient appliances was way off the scale making the scale
meaningless and confusing.

Efficiency does not relate to cost of running. As electricity is 4 times
more expensive to run than gas, an appliance using gas to heat the water
that is half as "efficient" as an all electric appliance is still cheaper to
run. Also as electricity is dirty to produce with only 30% efficiency from
station to point of use, the so-called "inefficient" gas using appliances
also far cleaner. Get it?