Washing machine temp question

louby40 · 30 December 2012 at 12:56PM

I have a decent washing machine which has the ability to lower the timings for each cycle.

I tend to wash most things at 40 degrees and I alter the time from 1 hr 20 minutes to a 40 minute cycle.

I could wash at 30 degrees for 1 hour 5 minutes.

Which would be more economical? 30 degrees for longer or 40 degrees for shorter?

Louise

I can also lower the 30 degree wash to 20 minutes but sometimes things don't come out completely clean!

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EricMears · 30 December 2012 at 1:15PM

louby40 wrote: »

I have a decent washing machine which has the ability to lower the timings for each cycle.

I tend to wash most things at 40 degrees and I alter the time from 1 hr 20 minutes to a 40 minute cycle.

I could wash at 30 degrees for 1 hour 5 minutes.

Which would be more economical? 30 degrees for longer or 40 degrees for shorter?

Louise

I can also lower the 30 degree wash to 20 minutes but sometimes things don't come out completely clean!

There may not be a simple answer.

If the machine is cold fill only, then it's always cheaper to run at lowest acceptable temperature since electrical heating costs a lot more than simple agitation.

However, if you can fill the machine with hot water then the relative costs of heating & agitation won't be quite so simple. There are water heating methods which are almost free (e.g. solar panels or a wood-fired boiler if you own your own woodland); electrical water heating will be even dearer than heating water in machine (water may cool between your tank and the machine); other heating metods fall somewhere in between.

Shortening cycle time always helps reduce costs - but not of course if you then have to re-wash half the load.

Cardew · 30 December 2012 at 5:05PM

If you have a water meter, then the cost of water is a bigger factor than the cost of electricity.

My machine - a cold fill Bosch - uses 0.4kWh or 0.6kWh on most washing cycles.(an occasional 0.9kWh) - so with electricity @12p/kWh say 5p or 7p for most cycles.

The water consumption varies between 59litres and 80 litres.

Water and sewerage costs vary a great deal across the country from under £2 to over £5 a cubic metre(1,000 litres) So taking an average price as £2.50, my water costs are 14.75p to 20p a cycle.

So you are better looking to see if there is a marked difference in water consumption rather than concentrating solely on electricity consumption.

Dave_Fowler · 30 December 2012 at 9:17PM

A very valid point about the cost of the water used by the machine. Not something I had considered. Thanks Cardew for drawing attention to this.

Most washing machine owner's operating instructions list the consumptions of electricity and water for each type of load so you can easily see which uses most electricity and water. For our Bosch machine it states for a full load (5kg) of cottons at 40 deg C: power consumption 0.46 kWh and water 51.6 litres. The same load at 60 deg C uses the same water but 1.02 kWh. Most other loads use around 35 - 45 litres of water for the wash + rinse cycle.

One point to note is that if you have to use the drying cycle and the machine has one of the condensing dryers (i.e. no external hot air exhaust pipe), the water consumption for the dry cycle is stated to be 30+ litres - almost as much as used in the complete wash + rinse cycle.

Dave F

nicter · 30 December 2012 at 10:30PM

I find when i have used a 30 degree wash items dont come up as clean. Sons shirts still smell "sweaty" under the arms. Not a problem at 40 degrees, therefore could be false economy

Cardew · 30 December 2012 at 10:39PM

Dave_Fowler wrote: »

A very valid point about the cost of the water used by the machine. Not something I had considered. Thanks Cardew for drawing attention to this.

In South West Water's area the customers pay £5.26 per cubic metre.

Some of the older washing machines can apparently use 150 litres on a cycle - so nearly 80pence a cycle.

Even reasonably modern and expensive machines can cost 30p to 40p a cycle.

grahamc2003 · 5 January 2013 at 12:45PM

EricMears wrote: »

There may not be a simple answer.

If the machine is cold fill only, then it's always cheaper to run at lowest acceptable temperature since electrical heating costs a lot more than simple agitation.

However, if you can fill the machine with hot water then the relative costs of heating & agitation won't be quite so simple. There are water heating methods which are almost free (e.g. solar panels or a wood-fired boiler if you own your own woodland); electrical water heating will be even dearer than heating water in machine (water may cool between your tank and the machine); other heating metods fall somewhere in between.

Shortening cycle time always helps reduce costs - but not of course if you then have to re-wash half the load.

Regarding the hot fill bit, what you say holds true if you actually get cheap hot water into your washing machine. If you have longish pipe runs, your hot fill may fill up with the cold water in the pipes, and stop filling when the hot water from the tank or boiler actually makes it to the washing machine, so you may still end up heating the water in the washing machine from cold, and taking hot water from the tank and put it in the pipes, a potential double whammy. This is partly the reason many washing machines are cold fill only, along with much less water use and lower temperatures.

Also shorter cycles aren't necessarily cheaper. Ignoring water costs (and thankfully I can do that since I'm not metered), the major cost is heating. If the lower temps are on a longer timed program - which I expect is sensible - then the longer program is likely to be cheaper.

That is the case for my dishwasher, where the eco cycle takes 2.5 hours, yet uses just over half the energy of the quick cycle which takes about 35 minutes, iirc.

jamesingram · 5 January 2013 at 3:38PM

i've heard of people with Solar thermal and a surplus of HW using a themostatic blend valve to fill cold only or hot/cold washine machines to get round the problem you mention Graham. Setting the blend valve to 20-30ish deg C and feed the cold fill with it . so all water entering the machine is hot(ish) ( with consideration to pipe run length) would be an attempt to make the most of availble free(ish) hot water.

ronangel · 30 January 2013 at 4:57AM

A bit off topic but a real money saver:
I have a modern LG washer dryer with electronic controls. I plugged it into a device that shows electrical consumption when I first got it,( I am electrical Engineer ) to work out the total electrical cost of each type of wash. I discovered that when switched off it still consumed 15 watts per hour on standby ( like leaving a small light on 24 hours a day!) In the same way as a TV set (1-2 watts) controlled via remote control, although the panel had no lights on. Always UNPLUG or switch off electricity EXTERNALLY to the machine after you have emptied it.
Note: DO NOT unplug modern digital flat screen TVs or Digital set top boxes/hard drive recorders as they automatically update their programming guides at about 3 am each day without fully switching on. If you do you will have to retune or risk not having the following 7 days of program information fully updated/be inaccurate and/or miss programs you have set to record when not there.

Cardew · 30 January 2013 at 10:18AM

ronangel wrote: »

A bit off topic but a real money saver:
I have a modern LG washer dryer with electronic controls. I plugged it into a device that shows electrical consumption when I first got it,( I am electrical Engineer ) to work out the total electrical cost of each type of wash. I discovered that when switched off it still consumed 15 watts per hour on standby ( like leaving a small light on 24 hours a day!) In the same way as a TV set (1-2 watts) controlled via remote control, although the panel had no lights on. Always UNPLUG or switch off electricity EXTERNALLY to the machine after you have emptied it.
.

That surely is atypical, if not faulty. Have you checked with LG, or your handbook. Does it tell you to switch off at the mains?

15watts is sufficient to produce quite a bit of heat - modern electronics require nowhere near that amount of power.

What it is the purpose of 'standby' on a washing machine i.e. standby for what?

ronangel · 30 January 2013 at 12:10PM

Cardew wrote: »

That surely is atypical, if not faulty. Have you checked with LG, or your handbook. Does it tell you to switch off at the mains?

15watts is sufficient to produce quite a bit of heat - modern electronics require nowhere near that amount of power.

What it is the purpose of 'standby' on a washing machine i.e. standby for what?

I have just rechecked the consumption and it is 14 watts at 230 volts ( 13 watts at 228 volts and 15 watts at 235 volts) this would depend on time of day and load on grid. The model number of LG is F1403YD5 I do not know exactly what this power is used for but see your point, It is probability used for “soft switching” where the mains goes through a power supply unit as in a computer with low voltage on panel switches. If you contact the manufacture to find out please let us all know the answer. I have had machine for 2 years and so far no problems, unplugging after each use.
I would be happy to dismantle the machine and take various readings to find EXACTLY where the power goes and what it is used for providing you with a short technical report. If this is required please Arrange to send martin £120-00p to cover my professional fees which he can donate to the charity of his choice. Upon confirmation from martin I will prepare report.
( Thought not..Grin). hopefully others will find this free tip useful.

Washing machine temp question

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