Your dishwasher saves you so much time in the clean up after cooking and mealtime, but you may be surprised to know it can also save you stacks on your utility bills. That's right – your dishwasher is not necessarily the energy and water suck you may think it is.
Although it's easy to think that washing dishes by hand is the more water-efficient method, a German study found that dishwashers use less water than washing by hand and can reduce your kitchen water consumption by hundreds of litres a month.
And because most of the energy used when washing dishes goes to heating the wash water, using a dishwasher is far more energy-efficient too.
In this article we take a look at what makes an efficient dishwasher, and how to maximise your energy and water savings while using one.
On this page:
- What makes a dishwasher efficient?
- Which type of dishwasher is more efficient?
- Energy use and running costs
- Dishwasher tips to save water and energy
- Are dishwasher energy star ratings reliable?
What makes a dishwasher efficient?
An efficient dishwasher is one that uses the least amount of water and energy to get your dishes clean to a level you're happy with.
It's worth noting that the most energy-efficient dishwashers in our latest review (those with a 'very good' energy efficiency score of 80% to 90%) tend to have lower scores for drying (in the 'good', 'OK' or 'borderline' range).
That's because dishwashers dry by building up a heat load in your crockery so the water will evaporate off. The higher the final rinse temperature, the better the drying performance.
But as heat requires energy, dishwashers that dry well tend to be more energy-intensive. Conversely, lower energy use means lower temperatures, and poorer drying performance.
The most energy-efficient dishwashers in our latest review tend to have lower scores for drying
Water efficiency is also linked to energy efficiency. Because most of the energy used goes to heating the wash and rinse water, it stands to reason that with less water to heat, a dishwasher will use less energy.
Of course, there's also a trade-off for performance – a dishwasher needs enough water to function effectively in each stage of its cycle. Manufacturers may reduce water consumption by deleting part of the program – they might go from three rinse cycles to two, for example. But this may mean the dishwasher isn't quite as good at getting your plates clean.
When considering dishwasher efficiency, it's all about balance. Higher energy consumption generally means better washing and drying performance, but higher utility bills. Conversely, a dishwasher that's really cheap to run may not do a fantastic job of washing and drying.
Ideally you should look for a dishwasher that's somewhere in the middle – one that washes and dries to an acceptable level, but doesn't brown out the neighbourhood.
Read more expert tips about what to look for when buying a new dishwasher.
How your choice of program affects efficiency
Your dishwasher has several programs, and they can vary significantly in terms of energy use.
When considering which program to choose, two of the most important factors to consider are:
- how dirty your plates are – heavily soiled plates require more intensive washing
- whether you're washing plastics – some plastics require higher temperatures to boost drying, while others may be damaged by high heat.
While all programs will use comparable amounts of water, the big difference in terms of energy use is wash temperature.
More intensive programs tend to be hotter, and as most of the energy used in washing your dishes goes to heating the wash water, this means the more intensive programs will use more energy.
It's worth experimenting to find the lowest temperature program that can get your dishes clean
When we test dishwashers in the CHOICE labs we use the default, auto or normal program. We tell you how well a dishwasher will wash and dry on this program, and how much energy it will use to do so.
This is a good starting point, but it's not the end of the story, because you can get better washing and drying performance by choosing a more intense, and therefore probably hotter, program.
Conversely, you can improve energy efficiency and reduce your running costs by choosing a lower intensity, lower temperature program. It's worth experimenting to find the lowest temperature program that can get your dishes clean.
Higher energy consumption generally means better washing and drying performance, but higher utility bills.
Which type of dishwasher is more efficient?
The good news, when it comes to standard-sized dishwashers at least, is that there's no difference in energy efficiency between dishwashers of different types.
Manufacturers typically make several versions of the same product to suit your needs – freestanding with worktop, built-under, semi- or fully integrated – and while the outsides are different, inside they have the exact same components and programs.
This means you can choose the style of dishwasher that fits your kitchen, without having to feel guilty about the environment or worry about a higher than expected energy bill.
Compact or slimline dishwashers can't fit as much in them, yet they use a similar amount of water and energy as standard-sized dishwashers
When it comes to compact or slimline dishwashers though, it's a different story.
Slimlines, with their 45cm width (as opposed to a full-sized model's 60cm frontage), just can't fit as much in them, yet they use a similar amount of water and energy to wash.
This means lower efficiency on a per-plate basis, and is why slimlines, and their similarly afflicted compact models, generally achieved just OK or even borderline energy efficiency scores in our tests. There was one exception, but predictably it did a lacklustre job of drying at the end of the cycle.
Even the most energy-hungry slimline or compact will be far more efficient than washing up by hand
That's not to say you should eschew a slimline model in favour of a full-sized one – chances are you're looking at a slimline because that's what's going to fit in your kitchen, and the cost of remodelling will far and away eclipse any perceived energy savings.
The choice comes down to what's going to work for your kitchen. Just remember that even the most energy-hungry slimline or compact will be far more efficient than washing up by hand.
Energy use and running costs
There's no doubt that dishwashers are more efficient than hand washing, but how much energy and water does your dishwasher actually use? And how much will it cost you to run over its lifetime?
Obviously it will vary depending on the model and settings used, but at CHOICE we've tested more than 430 dishwashers over the years, so we can tell you what fiercely frugal and energy- and water-intensive actually look like, as well as everything in between.
We've tested more than 430 dishwashers over the years, so we can tell you what fiercely frugal and energy-intensive actually look like
Program selection has a huge impact of course, but for benchmarking and comparison purposes we use the normal, auto or default program for our test. This is the most relevant program for consumers because it's what the majority of people use on their own dishwashers.
Here are some general results to give you an idea of how much water and energy a dishwasher can use.
To compare specific dishwashers based on actual energy and water usage as well as 10-year running costs, see our dishwasher reviews.
| Lowest | Average | Highest | |
|---|---|---|---|
| Energy use per cycle | 0.55kW | 1.04kW | 1.37kW |
| Water use per cycle | 10L | 14L | 21L |
| 10-year running costs | $883 | $1624 | $2102 |
TABLE NOTES: Results are taken from the 49 currently available full-sized dishwashers from our tests, based on tariffs of 40c per kWh for electricity and $2 per 1000 litres for water, using the default, normal or auto program. As of July 2023.
Difference in running costs explained
Why the big difference in running costs? It's primarily down to energy use. Even though we try to use readily comparable programs for our tests, manufacturers can configure this program differently depending on what they want to achieve.
For example, one manufacturer's 'normal' program may wash at 45 degrees celsius, whereas another manufacturer's 'normal' program might wash at 65 degrees celsius.
How temperature can affect performance
As well as the differences in running costs, we also see temperature-related differences in performance.
A washing machine with a hotter 'normal' wash will cost more to run, but will usually do a better job. And conversely, if your machine has a lower 'normal' wash temperature, it will probably be more efficient, but you may need to use a more intensive program to get results that you're happy with.
As mentioned above, you'll need to do some experimenting to find a balance between efficiency and performance.
One manufacturer's 'normal' program may wash at 45 degrees celsius, whereas another manufacturer's 'normal' program might wash at 65 degrees celsius.
Dishwasher tips to save water and energy
So you've done your homework and bought a dishwasher that rates well for energy and water use?
There's still more you can do!
Here are some handy tips for wringing the most out of your dishwasher.
1. Avoid hand washing anything you can put in your dishwasher
It might be tempting to wash that stray plate or butter knife, but resist the temptation and use the dishwasher instead. While we're at it, familiarise yourself with all the things you didn't know you could wash in the dishwasher too.
2. Skip the pre-rinse
Not only does it waste water, you may be tricking your dishwasher into thinking your plates are cleaner than they actually are, meaning it won't wash as well.
3. Run full loads
A dishwasher uses about the same amount of water no matter how much, or how little is inside it, so your efficiency per item improves with every extra cup or bowl you cram in (as long as you've stacked it so that water can reach every surface). And because a full dishwasher has greater thermal mass, a fuller dishwasher will have better drying performance too.
4. Choose the right size for your household
The fuller your dishwasher, the more efficient it is on a per plate basis, but for smaller households it may take several days to fill a full-sized dishwasher, by which time it could be getting decidedly whiffy.
That's where a compact model (45cm wide), or a dish drawer dishwasher can be handy, because with less capacity they generally use less water and because you'll fill them sooner, you'll eliminate the issue of dirty plates sitting around for a week.
A double dish drawer gives you the best of both worlds; run a single drawer for everyday use, or both drawers together after a big dinner party. Be warned though – the consumption figures on the star rating stickers are for a single drawer – double that if you're running both drawers.
5. Keep the filter clean
This helps extend the life of your machine, but also reduces the likelihood of food scraps being redeposited on your crockery, necessitating a second cycle.
6. Use the lowest intensity/temperature program that'll do the job
This requires a bit of trial and error, and there's no one 'right' program (more on this below).
7. Buy the right detergent
Dishwashing detergent is a major contributor to your overall running costs, and our dishwasher detergent reviews have found the most expensive products aren't necessarily the most effective.
8. Maximise your solar (if you have it)
If you've got solar hot water, buy a dishwasher with a hot water intake. That way your wash water is heated by the sun for free. If you have a regular solar system without solar hot water, you're better off choosing a model with cold water intake only and using your dishwasher when the sun is shining.
Are dishwasher energy star ratings reliable?
Energy and water star ratings (where applicable) are required for all products regulated under the Minimum Energy Performance Standards (MEPS) in order for the product to be legally sold in Australia.
Because these are a government requirement, the testing for the labels must be carried out in an accredited laboratory, which means they are very reliable.
But that's not the whole story.
Energy and water star rating labels only show the comparative energy and water efficiency of the program used for registration.
Provided they list the program and settings used, and that that program is capable of achieving minimum performance standards for washing and drying, manufacturers are free to use whichever program they like to calculate their ratings.
Energy and star ratings are very reliable, but they apply to just a single program
Because good star ratings sell more appliances, manufacturers will usually use the lowest energy consumption program that can do the job, even though it's probably not the one you're going to use in your own home.
Or to put it another way, the star rating labels just apply to a single program.
But of course dishwashers have many programs, and the other programs are likely to be more energy- and water-intensive. And while there's nothing stopping you using the registration program at home, most of us probably won't.
The story behind your dishwasher's 'eco mode'
As explained above, manufacturers can choose which program is tested for their energy and water efficiency rating.
In an effort to get the best rating possible, many manufacturers develop special programs designed to be just good enough to achieve the minimum washing and drying thresholds required for registration, while using as little energy as possible. And because 'registration program' doesn't sound all that appealing, marketing teams have cleverly renamed it 'eco mode'.
Because 'registration program' doesn't sound all that appealing, marketing teams have cleverly renamed it 'eco mode'
Is eco mode the solution to power-hungry plate cleaning, given it probably doesn't wash as well as other programs?
It just might be – and if you haven't tried eco mode, then it's worth experimenting with it.
If your plates come out clean then great! You've reduced your running costs and saved some money. And if not, well, the worst that can happen is you re-run the dishwasher on a more intensive setting – there's nothing to lose.
Stock images: Getty, unless otherwise stated.
