which is cheapest way to heat up water - Old Immersion or new washing machine?

JethroUK

I have my emmersion on 1 hour each night on economy 7 cheap rate
I have a fairly modern washine machine on each night on economy 7 too
The washing maching uses either hot water from the emmersion or heats up on its own
My question is which is cheapest way to heat up water - Old Immersion or new washing machine?

muckybutt

It depends on the Kw rating of the Immersion or washer.

If it's just hot water for using the washing machine you want then just use the washer as that will be the cheapest option, you will only be heating 7 - 9 litres of water compared to 250 litres in a hot water tank.

Alter_ego

muckybutt wrote: »

It depends on the Kw rating of the Immersion or washer..

Not really, more Kw will just do it faster.
The cost of heating water by electricity will be constant, as long as you are comparing the same price per Kw.
There will be losses to take into account, pipework, insulation etc. But the basic cost of heating it will be the same, and that was the question Jethro asked.

JethroUK

Alter_ego wrote: »

Not really, more Kw will just do it faster.
...

Just what I thought - but currently my immersion comes on at 5 a.m. and washing comes on at 6 am and starts off by using some of the hot water from the immersion

It wasn't until this morning when I was resetting the timers that the question popped up at all - Just wondering whether I got these timers the right way round - or are you saying it doesn't really matter

muckybutt

Alter_ego wrote: »

Not really, more Kw will just do it faster.
The cost of heating water by electricity will be constant, as long as you are comparing the same price per Kw.
There will be losses to take into account, pipework, insulation etc. But the basic cost of heating it will be the same, and that was the question Jethro asked.

I didn't quite explain that how I meant to but never mind

Norman_Castle

Just what I thought - but currently my immersion comes on at 5 a.m. and washing comes on at 6 am and starts off by using some of the hot water from the immersion

Depending on the distance from the tank the washing machine may be heating cold water from the pipes. I fitted a Y connector to make my washing machine cold fill only to avoid this.

Paul_the_Painter

Modern washing machines are child fill only, as it is more efficient for the machine to heat it's own water, taking into account length of pipes etc as Norman Castle says the machine is probably taking at least 1/2 of its water that is coming through the "hot" pipe, as cold water in any case. I'd just convert to cold fill only.

macman

If both immersion and w/m are heating on E7 cheap rate, and the hot wash cycle ends before the morning switchover to peak rate, it makes no difference. The kWh cost is the same.
Technically, the heat loss will be a bit lower heating 'on demand' in the w/m, but the difference would be pence per year.

Alter_ego

Paul_the_Painter wrote: »

Modern washing machines are child fill only.

Interesting concept!