Washing machine costs

Ultrasonic

BooJewels said:

Section62 said:

nannytone_2 said:

I've heard that washing at 30 degrees gives a considerable cost saving over washing at 40 degrees.
I have a 9kg washer and do 2 to 3 wahes a week.
My issue is that the full load programme washes at 40 degrees and takes 45 minutes,
The half load programme washes at 30 degrees and takes 30 minutes.

Is it more cost effective to do 3 full loads or 5 or 6 half loads?

Check the instruction manual - usually there will be a table showing the energy and water consumption for each programme (and sometimes each temperature option).

As Ultrasonic says, sometimes longer programmes use less energy (and water) by using soak time to do the cleaning rather than bashing the fabrics around so much.

When I was working this out for another thread, the motor of my own machine is 350 watts and the heater is 2100 watts, so the heating is the power hungry expensive bit, not the sploshing it about or even spinning.  So lower temperature and longer and slower in the machine would certainly use less juice.  My slow or gentle cycles only turn the load every few seconds, so for the most of that time, it's not using much energy.

I'm also not keen on stuffing the machine full either, I never fill it to capacity, it just doesn't feel like it can work properly and I'm also a fan of soaking - I often soak things [preferably very hot if they can stand it] overnight before washing them.

It's always a mistake to focus on power figures without properly factoring in how long different items are powered on for. My fridge freezer uses far more electricity overall than my kettle does, but the 3 kW power draw of my kettle when it's on vastly exceeds the maximum power draw of the former.

Section62

BooJewels said:

I'm not sure that it's that simple @adindas - that you can just work it out by time saved.  As I posted before you - the heating element in my machine uses 6 times the energy of the motor that turns it and there's a pump in there too - but I don't have the energy consumption for that.  So ten minutes saved in heating up the water (i.e. by lowering the wash temp) is worth a lot more than ten minutes saved on the time of the cycle.

Hopefully someone who knows how to work out electricity used v temperature can give a definitive answer.

And if people really need to make savings on their energy bill, a bit of additional effort might well be worth it for them.  I can afford my energy bill, but it makes sense to me to just not be wasteful - and I think a washing machine at over 2kWh is one of the big things.

Yes, the assumptions adindas made are wrong.

The reliable methods of finding out what the power consumption of each type of wash are wouldbe to check the manufacturer's instructions (hence my suggestion to nannytone_2), or to use a plug-in energy monitor to do your own measurements.

To further underscore Ultrasonic's last post, even when you take something like the drive motor rated at 350W you can't simply multiply that figure by actual running time, as the 350W would only be the rated power - the actual power consumption will vary throughout each start/run cycle, it won't draw a constant 350W.

nannytone_2

While I really appreciate all your advice, there is a fairly major detail that I failed to mention.
O am blind, so faffing about with settings isn't really an iotuin.
I always gibe my washing an extra spin, and know the 45 minute 40 degree wash is 5 ckicks down, and the30 minute 30 degree wash is 6 clicks down.
That's as technical as I can get

BooJewels

@Section62 - I appreciate that it's much more subtle and nuanced than my simplistic version, but it was just to illustrate that heating water to a higher temperature is the energy hungry bit of the process - and not just how long the wash cycle takes.  I'm not sure I'd say it was a 'mistake', it was more of an example.  My own machine manual didn't give any more detail than I posted in respect of energy consumption, so that may not be available for older machines.

A power monitor for direct comparison for an individual machine for a particular cycle is the only true solution - because it will also depend on factors like the temperature of the water coming in to the machine etc.

Apologies @nannytone_2 - that would make a difference to the advice given, so apologies if my replies were inappropriate.

nannytone_2

Don't apologise for something you couldn't have have known.
The fact that I want to hold onto a semblance of normality is my issue

BooJewels

Good for you @nannytone_2 it's funny how previously considered tedious tasks take on more importance when circumstances are different.  I'm going through something vaguely similar, in that my husband died and I'm having to find new ways of doing things on my own and having to learn how to do things I never had to before.  And then it becomes a personal challenge to try and manage something without asking for help.  And quite a triumph when you do.

I use smart plugs by TP-Link called Tapo - the P100 plugs are just smart plugs - a bit like a glorified timer plug, but they do a model up from that called a P110 which also has an energy monitor.  Mine are controlled using an app on my smart phone or tablet - so I wonder if this is something you could used yourself, if you have assistive technology.  I'm assuming that the P110 would also report the monitoring data in the app, so would allow you to get a definitive answer to the energy use per cycle, so you could continue to use the one that you can easily find but is most economical.  There are other brands of monitor of course.  Maybe someone who uses one can confirm if this would work via the app.

Obviously you'll have the initial outlay for the P110, which are around £10 - £12 each, but you might be able to use them for other things, they're still a smart plug too.  Plus they're seemingly in short supply at the moment.

It might just be that for your own ease in managing your laundry, doing what is generally easier for you personally might be a better option than trying to save a few pennies.

[Deleted User]

As suggested above, most manuals will have lab tested usage information.

Bear in mind that most washing machines are now cold fill. Our cold water supply is most certainly colder than it was 3 months ago as reflected in the daily power required to reheat my hot water cylinder.

DullGreyGuy

You need to check with your individual manufacturer as the math is more complex than the headline temperature. 

Our dishwasher has an eco and quick wash that both claim to be at the same temp but one is 50 minutes and the other 4 hours. Basic logic would say the shorter program is cheaper but actually its 50% more electricity and double the amount of water... thankfully the machine says the anticipated, and subsequently the actual, usage so you can decide if speed is worth the cost.

Our washing machine is more basic but did consider replacing it with the same brand as our dishwasher and certainly with them they said their 15 minute quick wash used more electricity and water than the 1.5hr eco wash ignoring the fact that it only does half the quantity.

BooJewels

@[Deleted User] - I'm going to repeat, in text form, the salient bits from your graphic for the benefit of the OP who is blind.

The graphic Dolor posted showed the energy consumption for 3 types of wash cycle as follows:

Standard 40°C cotton programme, partial load = 0.35 kWh
Standard 60°C cotton programme, partial load = 0.5 kWh
Standard 60°C cotton programme, full load = 0.8 kWh

adindas

BooJewels said:

@[Deleted User] - I'm going to repeat, in text form, the salient bits from your graphic for the benefit of the OP who is blind.

The graphic Dolor posted showed the energy consumption for 3 types of wash cycle as follows:

Standard 40°C cotton programme, partial load = 0.35 kWh
Standard 60°C cotton programme, partial load = 0.5 kWh
Standard 60°C cotton programme, full load = 0.8 kWh

Using maths to be more accurate it will need to modelled using a differential equation as it is a dynamic load (Keep changing)#. It is very complicated. Another method is direct measurement using Energy meter. But using this kWH figure above is much simple.

Now let compare it . Say the cost of electricity 30p/kWH

1. Standard 60°C cotton programme, partial load = 0.5 kWh. Cost = 0.5*30p = 15p.  But for 1 you will need to multiply it by two as you will need to do it twice so  2*15p = 30p

2. Standard 60°C cotton programme, full load = 0.8 kWh. Cost = 0.8*30p= 24p

So as expected 2 is cheaper than 1. But that difference is not significant.

It does not actually need a calculation  to proof that. If you need to do that twice with half load you will always end up with more expensive. Not to mention your valuable time for loading/ unloading, hanging it in airer, etc. Also the lifetime of your WM is shorter to be used more frequently.