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My electric washing machine has an express wash button (they seem a common feature) that reduces the washing time by a lot. My first thought would be that using it would save energy because of the much shorter time, but I'm guessing it has to do extra work to wash in a shorter time (faster spins?), so I could be wrong.

I've not measured the time difference, or looked at an energy meter because I'd like to know if there's a general principle I can apply.

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    I think the general principle here is to gather data by using an energy meter. That's the only way to know for sure how much energy is used. – THelper Oct 6 '15 at 19:15
  • @THelper knowing how fast a specific vehicle moves in practice by using a speedo doesn't mean it isn't useful to understand the principles of motion ;) – iain Oct 7 '15 at 2:33
  • Well, does it do extra work? I suggest you sample both programs to see what the differences are, if any. It's hard to determine if you do not supply a specific make/model. – Jan Doggen Oct 7 '15 at 7:44
  • @iain I don't think you have the right analogy there. How efficient a specific vehicle runs in practice from A to B is best decided by looking at how many litres of petrol it actually took. – Earthliŋ Oct 7 '15 at 12:48
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    From my recollection of Australia's Choice magazine (consumer reports equivalent) most washing machines are run half empty on the wrong wash cycle with far too much detergent, most of the time. So in practice anything you can do to reduce those errors will be a zero-cost fix. Viz, if you use less detergent, fill the washing machine with clothing, and use the correct cycle you benefit with no cost. Alternatively, half filling the machine and using the economy cycle is a compromise that will help (since most people buy machines for peak loads not normal ones). Also, wash clothes less often. – Móż Oct 8 '15 at 1:05
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I think a "general principle" is that "express wash" usually means one or more of the following

  • reduce the wash cycle
  • reduce the spin cycle
  • skip a rinse cycle (e.g. by not using any softener)
  • etc.

In other words, rather than "same washing in less time" you get "less washing", but still enough for not-so-dirty clothes to get clean.

This means that the total amount of energy is less, so express wash is more energy efficient.

(Talking about "general principles", a priori there is no immediate problem with hardly ever washing clothes, or washing them for shorter periods of time. But if dirty clothes would make you throw them away earlier, washing them on time may be more sustainable.)

  • Thank you for taking the time to consider this and answer. If I'm able to get hold of a meter at some point then I'll come back and provide the specifics too! :) – iain Oct 8 '15 at 22:19
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To supplement the existing answer, it's worth mentioning that using a hot wash may well incur more electricity costs in water heating than the washing machine incurs in actually washing, assuming you use electricity to heat your water.

According to this, 1 kilowatt-hour of electricity will only get you around 18 litres of hot water. I'd guess that most washing machines would use less than 1KWh of electricity for a cycle, but a full hot wash could easily use more than 18 litres of hot water. It pays to use a cold wash if you can!

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