How we test washing machines
We test almost 100 washing machines at our expert lab each year, but what goes on behind the scenes in our thorough washing machine tests and how is the score you see generated for each product?
Why our washing machine tests are different
Reviews you might read elsewhere online for washing machines might be based on the opinion of the store selling them or one user’s initial feelings about the machine. But they aren’t based on the thorough lab testing and assessments that we carry out at Which? – nobody goes to the lengths we do to find out which will be best for you.
As well as running multiple wash tests for each washing machine we review – we run wash programmes between six and 10 times for each washing machine we test – we also run dozens of ease-of-use assessments using a panel of three experts. The Which? overall percentage score you see alongside every review on our site is calculated purely from these test results.
We also buy every single washing machine we test and we don’t accept free samples of any machines.
What are Which? Best Buys and Don't Buys?
Best Buys are awarded to washing machines that impress us most in our tests. As of November 2019, a washing machine scoring more than 70% will be a Best Buy and comes with a firm recommendation, although you should still read our reviews for any weaknesses that might impact your buying decision. Meanwhile, washing machines that score less than 45% are Don’t Buys.
- tick the most important boxes – outstanding stain removal from cottons and manmade fibres, excellent spin cycles, effective rinsing and easy to use.
- tend to fall down in the most important areas – ineffective stain removal, spinning is too slow to be effective and detergent is left on clothes after the rinse.
What is a Which? Eco Buy washing machine?
If you want to make the most sustainable choice when next buying a washing machine, an Eco Buy is for you.
Eco Buy washing machines will have a lower impact on the environment over their lifetimes than other washing machines.
We calculate this in two ways: how energy efficient it is and how little water it uses. You can expect an Eco Buy to save you money on your energy bills as well as be kinder to the environment.
To become an Eco Buy, a washing machine must have:
- A total test score of at least 60%
- Three stars or more for energy efficiency on both cottons and synthetics washes
- Three stars or more for water on both cottons and synthetics washes
- Four stars or more for cleaning on both cottons and synthetics washes
How is the Which? score calculated
The Which? overall score is a percentage. The score only takes into account the results of our tests and ignores price completely. This means that all washing machines are tested on exactly the same scale, so you can compare any washing machine at any price and know how it measures up against its rivals in key areas. All washing machines are tested in the same way, regardless of the manufacturers’ claims.
Weightings and star ratings
A Which? overall score is made up of dozens of individual tests, from key factors such as overall cleaning, rinsing efficiency and ease of use, to energy and water use. Behind each of these ratings are dozens of measurements and checks. In the case of ease of use, we carry out more than 50 convenience assessments for each washing machine.
The most important aspects of a washing machine’s performance, such as how well it cleans clothes, will more greatly impact its score than whether the instruction booklet is easy to understand or whether the drum is easy to load and unload.
To keep things simple, the most important scores are shown as star ratings out of five on each washing machine’s Test Results page. This gives an easy-to-compare list of strengths and weaknesses, so you can quickly work out whether a washing machine is right for you.
A washing machine with a cavernous 12kg-capacity drum will be tested in the same way as a machine that can only hold 6kg of clothes. The bigger machine is likely to use more energy and water than the smaller machine, so we divide the energy and water used by the capacity of the machine in kilos to evaluate our results fairly for each machine on test.
How the overall test score is calculated
Our key testing criteria
Below are the key testing categories and how we evaluate each one:
Washing machine overall cleaning
Key question: Is this washing machine any good at removing stains from clothes?
Our cleaning tests are now tougher than ever, which means our Best Buy recommended machines are truly the best on the market for cleaning clothes. We challenge each machine we test to clean a range of stains, including tough-to-shift blood, grease, ink, milk, oil and rust.
We load the machines to 80% of their total capacity when washing on the cottons program and to the full capacity for the synthetics program.
We run our wash tests three times on each program. If any of the wash or energy results are wildly different between tests – or if one test run is much longer or shorter than the others – we will carry out two further test washes. And we do this on both the 40°C cottons program and the 40°C synthetics program. Most machines will end up being tested across six washes, but machines with variable results will be tested up to 10 times.
Overall cleaning makes up 50% of the score for all washing machines we test.
Washing machine rinsing efficiency
Key question: Will this washing machine rinse away all of the detergent or will some be left on my clothes?
To measure how well each washing machine removes detergent during the rinse cycle, we take freshly rinsed washing from the machine, just before the spin cycle, and spin it in a super-fast spin dryer. This dryer spins at 2,800rpm, roughly twice as fast as a typical washing machine.
After the spin, we collect water from the clothes and measure how alkaline it is compared with the alkalinity of the tap water used in the wash. Detergent is alkaline, so the greater the increase, the poorer the washing machine is at rinsing.
A machine that has been awarded one star for rinsing clothes might leave visible traces of detergent on your laundry. And in our tests, one in four cotton garments had bits of powder detergent on the fabric. Washing machines that provide a three-star rinse should not leave any visible traces of detergent behind. If you can see residue on your clothing, make sure you're not adding too much detergent to the washing machine. Washing machines that deliver a five-star rinse are the best we've seen at washing away detergent.
Rinsing makes up 15% of the score for all of the washing machines we test.
Washing machine spin dry
It's all well and good if a washing machine can clean clothes, but what about if it leaves them far too wet, making drying your laundry a total nightmare? That's why we measure how much moisture is left in the laundry each machine spins, so we can rate how well a machine will dry your clothes. We do this by weighing the clothes before they’re loaded into the drum and then again after they’ve been washed.
Spin dry makes up 15% of the score for all washing machines we test.
Washing machine ease of use
Key question: How easy is this washing machine to load, set and fill with detergent?
You'll be using your washing machine regularly, so you'll want to know it's not going to make doing the washing even more of a chore than it has to be. So, we look at every aspect of using a washing machine. Our 50+ ease-of-use assessments will cover reading and understanding the instructions in the manual, loading and unloading the machine, using the detergent drawer, the clarity of the control panel and display, selecting a wash program and operating the machine.
We use a team of three lab experts to rate everything from on a scale of very easy to very difficult.
Ease of use makes up 5% of the score for all washing machines we test.
Washing machine program length
Key question: How long will it take for this washing machine to wash a load at 40°C?
We time how long the cottons and synthetics 40°C programs take to run, so you aren't stuck with a model that is painfully slow at cleaning your clothes. The star rating we provide is based on the length of the programs and is relative to the capacity of the washing machine.
Program length makes up 5% of the score for all washing machines we test.
Washing machine noise
Key question: Is this washing machine too noisy to live with? Or will it be just fine in my open plan home?
All washing machines are a little noisy when they're running, but some are far louder than others, to the point where it makes carrying on a conversation or watching TV very hard in the vicinity. That's why we use a panel of five experts to test how noisy each washing machine is during its wash and spin cycles. A very quiet washing machine will earn itself five stars, while a very noisy machine will only pick up one. And we don't just assess the noise level, we also rate how intrusive and annoying the sound is, so that you can avoid particularly frustrating machines.
Washing machine energy use
Key question: Is this washing machine good, bad or indifferent when it comes to energy use?
We record how much energy each washing machine uses on both of the wash programs we test. We then work out a score for energy based on the amount of laundry they’re washing.
That way, we are able to fairly compare a large-capacity washing machine with smaller machines.
Energy use makes up 10% of the score for all of the washing machines we test.
Washing machine water use
Key question: How much water will this washing machine use?
As with energy, we record every drop of water a washing machine uses during our tests. We produce a star rating for water use, based on how much laundry is being washed in the drum. That way, we’re able to fairly compare large machines with smaller models.
Pick the perfect washing machine with Which? reviews
As you can see from the graph below, there is a wide variety in the scores of washing machines in the same price bracket. More-expensive washing machines tend to perform better, as you might expect, but we've found cheaper models that score higher than those that are much more expensive. So look beyond the price tag when you’re in the market for a new washing machine.