There's no question that dishwashers are efficient users of water – they're more water efficient than washing by hand – but how do they fare in terms of energy efficiency? Shouldn't you just look at the energy star rating to tell?
Well, it's complicated. And unfortunately energy star ratings aren't always a helpful way to tell how much energy a dishwasher uses (see below to find out why).
So what's an environmentally or budget conscious consumer to do?
CHOICE whitegoods expert Ashley Iredale talks us through the ins and outs of energy efficiency.
Plus, for CHOICE members, we'll tell you which dishwashers are the most energy-efficient, and which ones you should buy (hint: they're quite different lists).
Energy star ratings vs energy efficiency
The energy star rating system was designed to be a simple way to assess how energy-guzzling an appliance is. But unfortunately it's not quite as simple as it seems.
If you want an energy efficient dishwasher, you just look for one with a high energy star rating, correct? No.
"Good star ratings sell a lot of machines, because it's a clear signal to consumers about how efficient an appliance is," says Ashley.
We test using the default, normal or auto mode because that's what most dishwasher owners use, so our results will reflect real-world use
Ashley Iredale, CHOICE whitegoods expert
"Manufacturers know this and they want the best star rating possible, so they design special programs that just barely meet performance requirements to use as little water and electricity as possible. In an act of marketing genius they rebadge these registration programs as 'eco' modes.
"But we test using the default, normal or auto mode because that's what most dishwasher owners use, so our results will reflect real-world use. It's also why our energy and water consumption figures may be different from what's on the star labels."
CHOICE tip: If you look at the star ratings they'll actually state what program and settings were used when calculating the savings.
How energy efficient is a great wash?
Here's the bad news: if you want stellar performance, you'll probably need to give up on your dreams of energy efficiency.
"Our tests show that machines that dry the dishes well tend to be less energy efficient, indicating that good drying performance usually comes at the cost of higher energy use," says Ashley.
"That's because dishwashers use the last rinse cycle to build up a heat load in your crockery, which is how they dry – better drying means more heat, which uses more energy.
"Few dishwashers manage to score very well for energy efficiency when tested on the 'normal' cycle, which most people use."
It's a matter of having to compromise on either performance or energy efficiency
So it's a matter of having to compromise on either performance or energy efficiency, depending on what your priorities are.
"If you want better performance, select a more intensive program with the knowledge that it's going to use more energy," says Ashley.
"Equally, if you want to be more energy efficient, select a lower intensity program but be aware that performance may suffer."
How to find the most energy-efficient dishwasher
When you're shopping for a new dishwasher, don't just look at the energy star rating – it'll only give you part of the picture.
But don't buy solely on performance either if energy efficiency is important to you.
Try to find the sweet spot between energy efficiency and performance
A dishwasher that's energy efficient won't necessarily give you the best performance – and a dishwasher that delivers the best performance probably won't be especially energy efficient.
"There's an inverse relationship between energy efficiency and performance," says Ashley.
The energy/efficiency sweet spot
Your best bet is to try to find the sweet spot between energy efficiency and performance. We test for both performance and energy efficiency (as well as running costs, water use, energy use and more). To find the most energy-efficient, high-performing dishwasher, check our expert dishwasher reviews.
Or if you're a CHOICE member, read on – we'll share the most energy-efficient dishwashers, plus the top performers in our tests that are also efficient on energy.
If you're not a member, consider joining CHOICE to access thousands of independent reviews, or check out our free buying guides.
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