Washing at lower temperatures = save money

[PuzzledObserver]

TL:DR - wash at 20 degrees, save a packet. If you are already doing this, my apologies; posting in the hope that some people don’t realise how much of a difference it could make.

For about 5 years, I have been turning the temperature on my washing machine down from the default of 40 to 30. The washing still seemed clean, I assumed it would save me money and be good for the planet.

Just recently I have become intensely interested in how much electricity things use, trying to reduce unnecessary usage and move as much as possible times when it’s cheaper. So I have got used to how much various appliances use, e.g. using the oven and hob to cook a meal will use about 1.5kWh, the dishwasher and washing machine both use about 1kWh per cycle. My solar system has monitoring which means I can see the power being used every 5 minutes.

Then one day I looked at the 20 degree option on the washing machine and thought I would give it a go.

The result….. I can barely see the energy being used by a washing machine cycle. It used to draw about 2kW for 10-15 minutes. Now the heating cycle doesn’t even last long enough to get picked up by the 5 minute monitoring. Spin seems to use about 700W but only for a few minutes.

So instead of using 1kWh per cycle, it’s using about a quarter of that. So if you’re on the standard variable tariff of about 28p/kWh, that would save you 21p every time you put the machine on. If, as some forecaster are suggesting, electricity goes up to 40p/kWh in October, you would then save 30p per cycle.

Multiply that by the number of times your machine goes on per week, it will add up to quite a few pounds every month, which for many people these days could be significant.

Hope this helps someone.

I wonder why the manufacturers stopped the hot fill facility. I’ve got hot water sat in my tank, yet the machine fills cold and then heats it up.

I’ve been using 20C washing for some time and it is an energy saver. Great idea to post this tip.

However, I’m going to go all geek on you. Your observations sound like they are based on summer warm cold water that the washing machine doesn’t really need to warm up any further. If you track energy usage in the winter- when the cold water tap produces freezing ice cold water, you will note that the same cycle at 20C uses a bit more energy because the washing machine will have to heat the water a bit. (Of course, it’s still always less than a higher temp cycle.)

@KangarooKenny I don’t know why they did either, since heating water with electricity is almost always more expensive than using gas. Though for people who have a combi boiler and no hot water tank, they don’t have hot water just sitting there.

@Discovereads thats a fair point - I think I settled on 1 cycle being 1kWh in December and hadn’t revisited it since. So the saving may not be as much as I suggested, but hopefully still worthwhile for some.

I’ll recheck the dishwasher usage, although that’s not as straightforward to measure as the cycle is longer so it’s not easy to deduct the “normal” usage to work out how much the appliance itself is using. My dishwasher is already on the Eco setting. I imagine they still have to heat to a higher temperature to effectively sterilise things.

I’m going to buy an energy-monitoring smart plug and use it on various sockets round my house to find out where it would make the most difference to not leave things on standby (and then put WiFi controlled plugs on those, so they can be switched on a schedule and/or when my solar is going full belt.). But I can’t - or, rather, it would be very difficult to - put these on my DW and WM to accurately measure their usage because they are both integrated and the sockets are not accessible.

My dishwasher is already on the Eco setting. I imagine they still have to heat to a higher temperature to effectively sterilise things.

Dishwashers can’t really sterilise, most home units don’t get hot enough. So really, home dishwashers sanitise dishes. Also, the Eco settings are frequently below the temperature to effectively sanitise things. You need to wash at 50-60C and rinse at 82-88C to effectively sanitise your dishes. The temperature settings vary by manufacturer/brand so it’s best to check your user manual to see which cycles wash and which cycles sanitise.

Mmmmmm, food for thought. Off to put a 20 degree wash load on.

Modern machines only use a few litres for wash
the pipes from the tank through the house to the machine will have cold water sat in them
when they filled from hot and cold they took a mixture of both as machine didn’t know how hot incoming water was
by the time water run hot the machine has got what it need and the hot water is sat in the pipes wasted and going cold
it would save you nothing in fact cost you more as it’s wasted hot water from your tank and the machine still has to heat

I use everybody to download their appliance manuals. Within those manuals ( providing they are pretty recent ) you will find a break down of what each cycle/programme uses and hood much electricity/water is needed. It actually tells you the cheapest and most efficient wash. Often it is not what you expect. My most efficient wash is AA-+ rated but takes 3 hours!! Seems bonkers to me that the wash can take so long but be cheaper than a perfectly serviceable 14 m quick wash.

@devonianBiatch
Me too. It’s also part of my research before buying a new appliance. Because there’s no set regulation as to what “Eco” means so how “eco” they really are wildly varies.

Usually when there are discussions about washing at low temps you get a run of posters clutching their pearls about the germs that won't be killed and the fact that their DH come home covered in oil every day

The common sense approach of judging the washing requirements load by load seems to be lost on them

If the whole country moved down 10 degrees on each wash we'd save both money from our own budgets and help to save the planet

@devonianBiatch the other thing to read, of course, is the packaging on the detergent you use - both about its performance at different temperatures, and how much you need to use.

Off to do that myself….

Possibly stupid question but I’m guessing that wouldn’t work so well with actually dirty stuff (eg baby clothes that can be soiled etc)?

Do you find the detergent dissolves properly at lower temps? For some reason anything below 40 degrees is likely to leave lots of detergent foam in my machine and then I need to give the load an extra rinse cycle anyway.

Depends on your washer. Some brands do have an eco setting for a quick 60C wash which is the temperature you need to santise baby things.

I am interested in the dirty clothes question too.

at 20 will that effectively remove dirty from kids clothes or dp’s sweaty arm pit work teashirts?

does powder work at these low temperatures or would I need to use liquid?

You could test that out but as I said above doesn't common sense come into play and if you have a load that needs a higher temp then you use a higher temp for that one and lower to 20/30 for everything else

No one is suggesting that you ignore the actual washing and blindly use a lower temp for everything but modern machines and detergents work perfectly well at lower temps and with the rising cost of electricity it's an easy win

Slightly off topic

I've got an electric shower and a gas boiler with a hot water tank

Stopped giving the kids showers and gave them baths instead

Saving a fortune as I have already paid to heat the water regardless of if I use it

And the kids prefer baths too

That’s really helpful thank you - I don’t know that the manual was kept (it was delivered and installed when our twins were about a week out, so it was utter chaos) but I bet there’s a PDF version online. Thanks again.

Yeah I suspect it may be a case of using the 20 setting for our stuff and higher temps as needed for theirs. That’s helpful thanks.

I have started using a half dose of that Dettol laundry rinse (cotton scent) which disinfects when washing really dirty clothes at 20C. It works wonders against sweaty man armpits and teenage grime.

I've tried 30° washes but it just doesn't get through sweaty stinky teenage armpits. So their stuff is done at 40, and mine at 30. I may just try mine at 20, as I'm no longer a stinky teenager!

You may not have gotten a hard copy manual. We replaced our washer less than a year ago and it simply had a website listed on a static sticker…no manual delivered with it. So online pdf is a definite way to find the manual.

An eco /60c /quick programme...?

Eco programmes are longer (the cause of much debate on here, often, but it's the way things are) and 60c is never going to tick an eco box, so not sure how that works?

If you mean you can push a 'quick wash' button on your machine to shorten the length of a wash and you push that on an 'eco' programme, you are very likely to be negating the eco benefits by doing so. Same for overriding the temp on an eco programme.

My washing machine is pretty good at low temp washing however what doesn't wash well (TMI alert-heavily pregnant...) are my underwear and my husband's work uniform. Both of these washes go on a 30c at least but everything else I've found washes well at 20c, as long as the detergent is also adjusted accordingly

I didn’t know there was a 20c option oops! I haven’t noticed it, I have a Bosch machine. I’m abroad on holiday at the moment but will check when I get home. Definitely willing to give it a go if the option is there.

It's cheaper to fill and heat at the point of use than keep a tank full of water heated up and the lose heat from a tank as it goes down the pipes to the machine

It an energy efficiency thing