Electric use vs water use

[EnterFunnyNameHere]

Hi folks,

This is something I've been thinking about recently, and wondered what other people's take would be. I've been a longtime user of the eco mode on our washing machine. This uses less electric, but more water.

However, given recent trends of increases of drought - is this better? Our electricity is a green tariff, and water processing to make the clean water the washing machine uses probably is all fossil fuel... so is it better (if the energy is "green") to use a bit more electricity and a bit less water each time?

Obviously the bigger thing is to reduce using the washing machine as much as possible - which I'm already doing through being a slattern through and through 😁

What's the difference between eco mode and other modes in terms of electricity use.

Very interesting thought though.

@EnterFunnyNameHere I've just done a very quick check.

University of Oxford undertook a study with Thames Water the showed the energy required to treat 1000 litres of water was roughly 0.625kwh.

If energy consumption is roughly proportional to the assessed charge rate, the energy required to treat and resupply potable water (with a heavy bit of rounding) would be something like 1kwh per 1000 litres of water.

If your eco wash uses 50 litres that's 0.05kwh of electricity used by your water company.

I'm sitting in the garden on my phone so I could be waaaay wrong, but it doesn't feel ridiculous.

Conclusion - stick to eco mode.

Wow @Daftasabroom, THANK YOU. That's a great bit of sleuthing! If you can find it again, do you mind linking that study please? When I Google it I just get lots of news about people in Oxford protesting against Thames Water...

I might dig out the manual and see the guideline figures for electric & water usage across the different cycles and run some numbers (albeit I think it can vary depending on how full the machine is, it's as good a guide as any I suspect).

Thank you!

@EnterFunnyNameHere I can't get access to the full paper without logging into my work laptop, and copyright to rules would prevent me from me from sharing in any case.

I did find this, I haven't done anymore than read the title, so it may not be a lot of use.

Searching for half decent info on anything is fraught with risks. Id suggest you might like to try ChatGPT, don't take the results as gospel and double, triple check. But it's natural language, so if you're not used to googling by keyword and syntax it might be a lot simpler.

You raised a really fab question, I like good questions!

Does your machine handbook tell you how much water is used in each type of wash?

How great are the differences?

I have access to a fair few science publications through my work account, so I might do some further digging on there. Thank you!

So interestingly, according to the manual, the water use differences are pretty negligible- and actually the most heavy water usage is a normal cotton wash at 20oC when comparing a max load of 7kg.

However, if a water treatment figure of 1kWh/1000L is about right, the "best" overall might actually be the 20oC wash! Comparing 7kg load on each:

Eco is 0.7kWh + 55L water (0.055kWh) = 0.775kWh. This equates to cost (for interest!) of (0.7kWh x 59.46p)+(55L x 0.19368p)=£0.52

Cotton at 20oC is 0.35kWh + 69L water (0.069kWh) = 0.419kWh. Cost-wise this is (0.35kWh x 59.46p)+(69L x 0.19368p)=£0.34

Unless my maths is way out of course!!

I was wondering about this. I always use eco mode unless I’m in a massive hurry (forgotten to wash the kids PE kits) then I do one of the quicker washes. I always wonder if I’m doing the right thing.