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How do washing machine star ratings work?

Why ratings for energy and water use rarely tell the whole story

energy rating sticker on front loader washing machine
Last updated: 09 August 2019

Need to know

  • Energy and water star ratings are very important, but they’re calculated on a single program so may not give the full story
  • Manufacturers want their washers to scrape past the minimum performance requirements because this gives them most stars
  • Washing cycles are getting longer because this enables manufacturers to ‘game’ the system and earn more stars

Earth, air, wind and fire – we're all familiar with the classical elements. But there are four completely different elements to consider when evaluating washing machine performance – dirt removal, spin performance, rinse performance and gentleness on your clothes. 

And they don't just inform how well a washing machine performs. There are also minimum thresholds for each of them when calculating a machine's energy and water star ratings. 

A good star rating sells a lot of washing machines, so manufacturers pay very close attention to them when developing and registering a new appliance.

How are star ratings calculated?

Under the Australian standard, a washing machine must be able to wash a full load of laundry to defined minimum standards in each of the elements listed above (dirt removal, spin performance, rinse performance and gentleness).

To test a washing machine, it is loaded to its maximum claimed capacity using an Australian standard cotton load made up of a laundry list of items, with soil and fray swatches attached, and then run on a warm program (minimum 35°C).

At the end of the cycle, the performance is measured to ensure it achieved the threshold required for each element, and the energy and water used is recorded. These figures, in a ratio with the machine's capacity, inform the energy and water star ratings.

Why top loaders use less energy

Because the Australian Standard specifies a warm wash, the energy rating also factors in the energy used to heat the wash water. 

For front loaders with built-in heaters, this is all the one measurement. But top loaders typically don't have their own heaters, so do they get an advantage?

No, because the figure on the label is calculated including an estimate of the energy your home's hot water system uses to heat the amount of hot water the machine takes in during the test. 

That's why front loaders are typically more energy efficient, despite common sense telling you their much longer cycle times would use more energy – because they use much less water, and need much less energy to heat it.

If you think washing cycles are longer than they used to be, you're right

Never ending cycle?

Speaking of cycle times, if you think they're longer than they used to be, you're right. And part of the reason is the star rating system. 

Manufacturers work hard on tweaking their rating program to use the least amount of water and electricity to wash the largest load possible, while still meeting the minimum performance requirements. 

If they do badly in one of these elements, they simply don't pass. And if they increase their water or electricity use, they're penalised.

But the one thing they can't be penalised for is time. So if they're not meeting a given threshold, they can just make the wash cycle longer until they do, with no loss of star rating.

Alternatively, they might already meet the requirements, but want a better water rating. So they tweak the program to use less water and compensate for the resulting performance drop by circulating that water for longer.

The 'dark art' of getting most stars

In a similar vein, the star rating labels actually create a perverse incentive to manufacturers not to improve the performance of their products. Or rather, instead of incentivising them to make their washing machines really good, it incentivises them to make it just good enough. 

What do we mean by that? Under the star rating system, a washing machine must achieve a minimum performance standard, but there's no bonus for exceeding it. 

When they're developing a washing machine, manufacturers have total control over how the appliance works – they can play around with settings, temperatures, speeds, soak times and virtually every aspect of how the washing machine works. So they can generally make their machines wash and rinse way better than the version they bring to market.

So why don't they bring them to market? Because the machines would use more energy and more water, which means fewer stars – and less appeal to consumers. 

The dark art of getting the most stars, then, is to program a washing machine that only just passes the registration test – not one that exceeds it with flying colours. We're not saying every manufacturer adopts this philosophy, but they're certainly well aware of it.

What it means for you

What does this mean for you? Well, your washer will do what it says on the tin, or probably even better, as far as energy and water consumption, and that's a good thing. 

And because Australians for the most part wash essentially clean clothes it'll do a good job of getting them clean again, but for heavily soiled clothes and nasty stains you're probably going to benefit from using a pre-treater or laundry soaker, and contrary to our usual advice, wash smaller loads. 

Oh, and your washing might take a little longer than it used to back in the day, but you can use that time to meditate on the environmental and cost benefits that come from improved water efficiency.

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