How we test dishwashers

We’ve been testing dishwashers since 1960. The Colston Mk4 was the first to become a Which? Best Buy in 1965. Today we test more than 60 models in our specialist laboratory each year, cleaning around 28,000 dirty dishes, glasses, cups and pieces of cutlery. 

We don’t accept any freebies or samples – we buy every single dishwasher that we test direct from retailers, just as you would. Our reviews are as independent and unbiased as they are rigorous and robust. 

Other review sites typically use an individual tester and generate scores based on their preferences. At Which?, each dishwasher undergoes around 200 checks and assessments to give it an overall score – we rely on science-backed evidence, not opinions. 

And if it’s bad, we don’t hesitate to give it a Don’t Buy warning.

We’ve tested the latest models to help you choose the best dishwasher for you and your kitchen

Cleaning: Does it blitz through grease and dirt?

To test how well each dishwasher cleans, we stack them with a range of dirty dishes, glasses, mugs and cutlery. Our menu of challenging grime includes milk, coffee, eggs, pasta, spinach and margarine. 

Our appliance testing experts put dirty dishes in a heated cabinet to really bake on the dirt. This simulates them being sat on the side or in the dishwasher for a day before being cleaned. Some mucky crockery is left to air dry on the side, too. 

We also add some clean dishes to the load to see if the dishwasher transfers grime from one plate to another. After washing, we inspect each item in the load and score it for cleanliness.

While your dishes may not be as heavily soiled as the dishes we test, it means we can give dishwashers a really tough test to find the best. 

What separates a good result from a poor one?

A dishwasher with a five-star rating for cleaning will leave everything practically spotless, although you may spot small traces of stubborn stains, such as pasta or egg, on the odd dish here and there. On the other hand, a dishwasher with a one-star rating will leave most dishes heavily soiled and transfer dirt onto the clean dishes too.

Drying: How well does it dry dishes?

Our lab technicians inspect how dry each dish is after the cycle ends, because nobody wants dripping lunch boxes and watermarked wine glasses.    

Once the program has finished, dishes are left in the dishwasher for 30 minutes with the door closed, unless it opens automatically. Each dish is inspected by our technician for water droplets and then given a rating out of five stars for dryness. We use spotlights to ensure no drips or moisture are missed.

Both of our cleaning and drying tests are repeated twice to ensure our results are consistent. If there are any anomalies, we’ll run up to two further tests to ensure accurate results. 

We also test the drying efficiency for plastic dishes and give that a separate star rating, because some dishwashers struggle much more when it comes to drying plastics compared to ceramics. If you do a lot of meal prepping or pack a lot of lunch boxes, this is something you might want to look out for. 

What separates a good result from a poor one?

A five-star dishwasher will leave dishes dry and ready to pop straight back into the cupboard, whereas a one-star model will leave items noticeably wet, so they may need additional air drying or wiping with a tea towel. Remember to check the separate star rating for drying plastics – three stars or below usually means dishes are considerably wet.

Energy and water use: How efficient is it?

We don’t rely on the energy label, because they’re almost always based on the eco program, which you may not use all the time. We run our own energy and water-use tests to find out how efficient a dishwasher really is during everyday use.

Our lab technicians calculate how much energy is used during the main program, which is likely to be the most commonly used setting. But we also test the energy-saving or eco programs for those who want to make an extra saving while running their appliance.

The most water-efficient dishwasher we’ve tested uses around half a litre of water per place setting, while the worst uses more than three times that amount. 

We also calculate the exact annual running cost for every model we test, based on running the main dishwasher program five times per week for a year. We found that the most expensive dishwasher to run costs more than double the cheapest in energy costs. 

What separates a good result from a poor one?

A five-star rating means the dishwasher uses resources efficiently, while a one-star rating means it uses energy or water excessively, which can inflate your bills more than necessary. 

Dishwashers do, of course, require energy and water to clean well, so the most efficient aren’t always the best. Those that manage to pull off brilliant cleaning while being efficient get our Eco Buy recommendation. 

Ease of use: Is it easy to load and use?

We load dishwashers with the kind of stuff you most often want cleaned: dinner plates, bowls, glasses and cutlery. But we also add a collection of more oddly shaped items, including a saucepan and water jug, to check how much of a hassle it is to get them in and out of the dishwasher.

Our lab technicians assess how easy it is to fill and empty each dishwasher to capacity, and whether it can accommodate large plates and long-stemmed wine glasses. We've found that some slimline and table-top dishwashers can be harder to fill to capacity than their larger counterparts, although some full-sized models are a real chore to load, too.

Clear, well-labelled controls that make programming easy get the thumbs up from us. And because a dishwasher is only truly great if it's effortless to use, we also check how easy it is to open and close the door, refill the salt and top up the rinse aid.

With more and more models including foldable prongs and other ways to make loading flexible, we now assess this and include it in our overall rating. For example, we check if you can fit in large plates and tall glasses at the same time.

What separates a good result from a poor one?

A five-star dishwasher will be simple to load, with clear programs and controls, and easy-to-access dispensers for salt and detergent. On the other hand, a dishwasher rated two stars or below for ease of use will be difficult to load, lack space and offer poor support for wine glasses.

Quietness: Does it make a racket while running?

Dishwashers don't tend to be as loud as other appliances, such as vacuums, but a quieter model is an important consideration for those whose dishwasher sits in earshot of areas where people eat or relax. 

We use a mixture of subjective and technical assessments to assess how noisy the dishwasher is. First, we install the dishwasher in a kitchen, and if it’s an integrated model, we cover the sides and top just like it would be fitted in your home. Using a sonometer, we record noise levels during the wash phase.   

A panel of three experts also evaluates how noisy the dishwasher is and notes down any disturbing sounds, such as humming, buzzing or whirring.

What separates a good result from a poor one?

A dishwasher with a five-star rating will be almost silent and won’t disturb you while it's running. But a one-star rating for quietness means you’ll hear disruptive and loud sounds, such as whirring, buzzing, humming and other mechanical noises. A three-star machine might not be loud, but could present you with a cacophony of sounds that constantly shift and change annoyingly.

Spare parts: How easy is it to fix?

We recently introduced a spare parts rating for key manufacturers, so members know how easy it is to source a part if something goes wrong. 

Our in-house experts looked into common dishwasher parts that may need replacing, including filters, cutlery baskets and spray arms, checking the price and availability of the original spare part from manufacturers’ websites. We then rated how easy it is for you to replace these parts yourself at home. 

The guarantee period for the dishwasher also forms part of the overall score, along with data from our annual reliability survey, where we asked more than 3,500 people if and when they’ve experienced faults with their dishwashers. We also took into account the helpfulness of the instruction manual and the manufacturer’s website. 

Based on the research, we rated each dishwasher brand with a star rating from one to five.

What separates a good result from a poor one?

If a dishwasher has a five-star rating for spare parts, they should be reasonably priced. It should generally be easy for members to source the original part on the manufacturer’s website and fit it themselves at home. A one-star rating means the spare parts are not available on the manufacturer’s website or are difficult to buy, so members may have to use a third-party website or source a universal part. 

Which? members can filter all our dishwasher reviews by cleaning, energy efficiency, ease of use, quietness and more of our expert test results.

How we calculate the scores

The price of the dishwasher is not a factor in the score, because all of our dishwashers are tested in the exact same way. You can easily compare a dishwasher's performance, regardless of the price and brand.

Here’s how the weighting for each element of the test breaks down: 

• Cleaning (42%)
• Drying (18%)
• Energy and water use (20%)
• Ease of use (15%)
• Quietness (5%)

How we choose the products

Our market analyst carries out extensive research to sift through the hundreds of dishwashers on the market and identify those that our members want to see tested. We also test models at different prices, ranging from around £250 up to nearly £1,400. 

We invest nearly £40,000 every year into buying dishwashers to test – and we never accept freebies from manufacturers or retailers – so that our reviews and recommendations remain fully impartial.

Is it a Best Buy dishwasher? What our verdicts mean

The Which? overall percentage score is calculated purely on the measurements and ratings supplied by our laboratory experts, meaning there's no room for unconscious bias when giving an overall rating. 

Our recommendations are designed to help you choose a dishwasher at-a-glance, but it’s always best to read our reviews to find the perfect appliance for your home.

Best Buy-recommended dishwashers

Best Buy dishwashers impressed us the most in our tests. Any full-size dishwasher that scores 79% or more and gets five stars for cleaning performance is a Best Buy. 

These tick the most important boxes – fantastic cleaning and drying, simple loading and unloading, and efficient use of energy and water – and come with our firm overall recommendation, although you should still read our reviews to check for any weaknesses that might impact your buying decision. 

For slimline models, the threshold to get a Best Buy is 71%. As slimline models don't tend to perform as well on average compared to full-sized models, slimlines can score four stars for cleaning and still get the badge. 

Eco Buy-recommended dishwashers

If you want to make the most sustainable choice when next buying a dishwasher, an Eco Buy is for you.

Eco Buy dishwashers will have a lower impact on the environment over their lifetime than other dishwashers, as well as keeping your energy bills low. 

To become an Eco Buy, a dishwasher must have:

• A total test score of at least 65%
• Five stars for energy efficiency for its main and eco programs
• Five stars for water efficiency for its main and eco programs for full-sized models
• Four stars and above for water efficiency for main and eco programs for slimline models
• Five stars for cleaning with full-sized models, and at least four stars for slimlines
• The brand must get at least a three-star reliability score in our annual dishwasher survey, and only 20% or fewer of its dishwashers develop a fault in the first six years of ownership

Great Value-recommended dishwashers

Great Value dishwashers combine good quality performance with a budget-friendly price. 

To qualify, a dishwasher must first score at least 65%, and be significantly cheaper than the average price for tested models of its type, whether that's freestanding or integrated, slimline or full-sized. 

Any model that meets the criteria is named a Great Value product, and you can be sure it will keep you and your wallet happy. Some Great Value dishwashers might also qualify as a Best Buy, but it's not required for the badge.

Don’t Buy dishwashers

Any dishwashers that score less than 45% are named Don’t Buys. These fall down in important areas – they will leave dishes dirty and wet, may have filters that block easily and are often tricky to use.

To find out which dishwashers qualify, head to our dishwasher reviews and use the Best Buy, Eco Buy and Great Value filters to find the best model for you.  

Our dishwasher experts

The Which? dishwasher team works alongside our lab experts to ensure that testing reflects how members actually use their dishwashers at home, as well as turning complex scientific data into simple, informative reviews. Here's the team behind it all: 

• Humairaa Habib, senior researcher and writer: Humairaa interprets technical lab reports to produce helpful and insightful dishwasher reviews, ensuring they’re to the point, so that our members can make informed buying decisions. She also provides advice and recommendations to members based on our data-backed evidence. 
• Victoria Purcell, home editor: Whether it’s a product review, maintenance advice or the latest news, Victoria makes sure what you're reading is clear, helpful and informative so that you can buy and use your dishwasher with confidence. This means keeping an eye on what's trending in dishwashers – be that auto-dosing or extra-dry programs – and seeking out the answers to key consumer questions.
• Dr Steph Kipling, science team manager and dishwashers scientific adviser: Steph analyses hundreds of data points in our laboratory reports to calculate the scores, star ratings and running costs for every dishwasher we test. Her rigorous analysis identifies the dishwashers worthy of our Best Buy and Eco Buy recommendations, as well as the Don’t Buys that will leave you reaching for the washing-up bowl. She also helps develop and refine our test programme.
• Adishree Sharma, senior market analyst: Adishree carries out extensive market research, both online and in-person, to ensure we’re reviewing the dishwasher brands and models that our members are genuinely interested in. She keeps tabs on both established and emerging brands, and anticipates any market trends or changes to ensure our content stays relevant.