Washing machine spin speed efficiency figures and drying costs
Here are some interesting figures (from an tumble dryer user manual) which give us an insight into the effectiveness of faster spin speeds . The figures are based on a 6kg capacity drum size and an efficient condenser dryer and show the residual dampness in laundry (cottons) after being spun at various speeds.
They also (much more interestingly) compare the difference in energy that’s required to tumble dry the laundry after spinning it at at say 1200 rpm compared with if it was spun at 1000 rpm or 1400 rpm.
Results would vary between different washing machines and tumble dryers, but they do give an accurate representation of the differences between the efficiency of different spin speeds, which I suspect is much less than most people are likely to expect, and the main point of this article.
|Spin Speed||Residual Dampness||Energy Used to Tumble Dry|
(based on a modern A rated condenser tumble dryer)
These figures imply there is little advantage to paying much more for a 1400 spin washing machine over a 1200 spin washing machine, which I’ve seen as high as £50 more. These figures show that the difference in dryness between the two after spinning cottons is just 3% and it would cost only .2 of a kWh extra to tumble dry cottons spun at 1200 instead of 1400 (roughly 3 pence – NOTE: This calculation was done before all the recent electricity price rises of late 2008). Most other fabrics would have the same water extraction regardless of the washing machine’s spin speed because only cottons are spun at the top speeds.
Electricity charges can vary quite a lot these days but on the UK Power electricity running cost calculator the average cost per kWh is set at 10 pence so I’ll use that figure. That means drying a load of cottons spun at 1200 would use 3.3kwh in electricity, 3.3 x 10p = 33 pence . If using a 1400 spin washing machine which costs up to £50 more to buy, it would cost (3.1 kWh x 10p) 31 pence to tumble dry – a mere 2 pence cheaper. You would need to tumble dry such a load 2,500 times to recoup the extra cost in buying the 1400 spin washer if you paid £50 more for it.
Spin speeds are good marketing tools
Washing machine manufacturers have long since used faster spin speeds as a way to increase sales and command higher prices. Most people believe faster is better, and “better” is worth paying more for, but the difference between an 1100 spin speed and a 1200 spin, or a 1200 and 1300 and even 1400 are pretty negligible. To make a significant difference in the amount of water extracted you have to have much bigger jumps than one to two hundred revolutions per minute.
Why does this matter?
Slower spin speeds mean –
- Cheaper washing machines
- Quieter washing machines
- More stable washing machines
- Longer lasting washing machines because there’s less wear and tear on the bearings, motor, carbon brushes, suspension etc.*
- Gentler on laundry
* The point about longer lasting washing machines has been somewhat diminished by the throwaway washing machine problem afflicting the majority of washing machines these days. This is because the price of parts is often extortionately high, which makes many of them artificially uneconomical to repair and prevents them lasting any where near as long as they would otherwise last.
Faster is definitely better but..
I appreciate that faster is better up to a point. Even if faster only gets a fraction more water out then arguably it’s preferable. But what I’m saying is that because faster comes at extra cost, and with several disadvantages it is not better per se – all the time, and for every one. As you get faster, the quality does not increase – but the cost, noise, how much it jumps around, wear and tear and even how long it will last all get affected so should be taken into account.
What about 1800rpm?
It’s only when you jump from a 1200 spin washing machine (the current most common speed) to 1800 rpm that you see a more tangible benefit. If comparing the costs of tumble drying after spinning at 1800 rather than 1200 then it would use 2.6 kWh instead of 3.3 kWh. That equates (using the 10p per kWh figure) to 26 pence instead of 33 pence – a saving of 7p. However, an 1800 spin washing machine could easily cost £100 more than a 1200 spin. This would mean someone tumble drying 2 or 3 loads a week would take about 9 years to get a £100 premium purchase back. You should also factor in the fact that an 1800 spin washing machine may be subject to more wear and tear because of the extra speeds involved.
Of course this argument is based on tumble drying laundry. If not tumble drying then the only difference is that it will take a bit longer to dry on the line or in the spare room next to the radiator but at no extra cost. In this scenario the cost issue is replaced by a convenience issue, which for some will be negligible though for others it could be more significant if having laundry drying in the house is inconvenient.
What about the argument that using less electricity is better for the environment?
That’s a fair point. From an environmental point of view it is better that we all pay £100 more for a washing machine and use less electricity if tumble drying – even if the electricity saved is a fraction of the extra costs buying the faster spinning washer. This is a very different argument to the personal economic considerations covered above and is based on the premise that regardless of the cost to the consumer, the less electricity we use the better.
However, as with many environmental arguments, the whole picture needs to be taken into account and all too often it isn’t. If faster spinning washing machines aren’t built to a high enough standard, and break down more often, or just don’t last as long, then the whole environmental benefit is compromised and the scales could even tip the other way.
Many of the most common washing machines are not made to a high enough build quality to cope with very fast spin speeds. They can be noisy, bounce around too much, refuse to spin many loads at full speed because of over-protective and less sophisticated out of balance systems, and parts can wear out or fail quicker and more frequently.
For the average person buying an averagely built washing machine, 1200 should be the best compromise between drying efficiency and cost, noise, stability and wear and tear. The figures above show that a 1400 spin washer doesn’t get that much more water out. I wouldn’t say avoid a 1400 but you would need to decide how much extra you are paying for the extra 200 rpm and if the extra cost is worth it. If buying a cheap washing machine, 1600 is way too fast in my opinion because they aren’t built any better than the 1000 spin versions they used to make. Maybe even 1400 is too fast for some washing machines these days. (related: Washing machines exploding – what’s going on?)
If you use a tumble dryer excessively it may be worth considering a higher spin speed but again, the figures show that you may need to jump to an 1800 spin to get a significant difference, and currently an 1800 spin is likely to cost so much more it’s debatable whether you will save much money at the end of the day unless you tumble dry all the time. It will still save some drying time though.
At the end of the day, as is often the case, trying to look at the bigger picture is complex and there are many variables that make it impossible to advise a common best tactic. The main thing is to not get carried away thinking faster is definitely better and ask why manufacturers make washing machines that spin at so many different top spins when surely there has to be an optimum that should mean all washers should spin at the same ideal spin speed. It costs virtually nothing extra to make a washing machine spin at a top spin of 1000, 1200 or 1400, with spin speeds often set artificially by simply configuring the same pcb differently.
- Washing machine spin speeds
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The arguments in this article are based on electricity charges being at certain (quoted) rates. If electricity charges increase significantly it may affect the argument. At the end of the day if you can follow the argument and factor in the amount you are paying for your electricity you can decide for yourself.