How we test electric kettles
Buying a new kettle? Find out how our in-depth testing helps you to get the best
kettle for your kitchen
Our independent reviews tell you everything you need to know about a kettle before you buy it. But how do we actually test them, and what makes Which? tests the most rigorous around.
Unlike most free-to-access websites, which typically get kettles free of charge directly from the manufacturers, we buy all the appliances ourselves so you can have complete trust that our verdict is independent.
As well as using multiple testers in a lab, the Which? overall percentage score is calculated purely on the measurements and ratings supplied by the lab, meaning there's no room for bias when giving an overall rating.
Head to our round-up of the best kettles to see our latest top picks.
Video: How we test kettles
Watch this video to discover more about our extensive testing programme and why our kettle tests are different.
What are Which? Best Buy, Great Value, Eco Buy and Don't Buy kettles?
Our recommendations will help you to narrow down your shortlist, but you should still read our full reviews to check for factors that might impact your decision.
Best Buy kettles
Best Buy kettles typically do well in most if not all of our tests, scoring 73% to earn the recommendation. They'll probably be quiet but speedy to boil, easy to use and have good limescale filters. Most Best Buy kettles also have a comparatively low minimum fill and won't waste energy by overboiling.
Great Value kettles
Some Great Value kettles also score high enough to be Best Buys or Eco Buys.
Eco Buy kettles
Eco Buy kettles are a more sustainable option compared to other kettles, so they'll help you to reduce your environmental impact and save you money in the long run.
We calculate whether or not a kettle deserves to be an Eco Buy in a few different ways: how quickly it boils, how low the minimum fill is, and how long it's likely to last without developing a fault.
To become an Eco Buy, a kettle must have:
- A total test score of at least 65%
- Five stars for speed of boiling
- A minimum fill of 275ml or less
- An overboil time of less than five seconds
- The brand must have a good longevity rating in our annual consumer surveys.
Fewer than 10% of the kettles we test are sustainable enough to be Eco Buys. To find out which ones make the grade, head to our kettle reviews and use the Eco Buy filter.
Don't Buy kettles
Kettles that score less than 45% are Don't Buys and should be avoided at all costs.
How the Which? score is calculated
The Which? overall score is a percentage; it only takes into account the results of our tests and ignores price completely.
This means that all kettles are tested on an equal scale, so you can compare any model at any price and know how it measures up against its rivals in key areas. All kettles are tested in the same way, regardless of manufacturers’ claims.
Weightings and star ratings
A Which? test score is made up of dozens of individual tests and checks on key factors such as speed, quietness and minimum fill, as well as ease of use and cleaning.
To keep things simple, the most important scores are shown as star ratings out of five on each kettle's test results page as an easy-to-compare list of strengths and weaknesses, so you can quickly work out whether a model is right for you.
The most important test results have a greater impact on a kettle's overall score:
- 30% ease of use
- 20% speed
- 15% overboil time
- 15% minimum fill
- 15% limescale filter
- 5% noise
Our kettle testing criteria
Here are our six key testing criteria and how we evaluate each one:
1. Ease of use
Key question: is the kettle easy to use?
Our expert panel pours cup after cup, filling each of the kettles to a number of levels, including their maximum and minimum, to assess how easy they are to lift, fill, carry and pour.
We look at the water gauge on each kettle – kettles with large, clearly marked windows on either side, which allow you to see how much water is in it, get the highest marks
We also check whether the kettle shows finger marks, how easy these are to remove and how easy it is to clean the inside of the kettle.
Ease of use accounts for 30% of the total score.
2. Speed
Key question: how quickly does it boil?
We fill each kettle with 1L of water at a temperature of 15ºC, and place a temperature probe into the centre of the water.
We then boil the kettle, recording the temperature reached at the time it automatically switches itself off and how long it takes. We test each kettle three times to get an average boiling time and temperature.
The fastest kettles can boil 1L in 2 minutes 18 seconds, while the slowest can take nearly twice as long, leaving you waiting around for your cuppa.
Speed accounts for 20% of the total score.
3. Overboil
Key question: does it waste energy by overboiling?
We boil 1L of water in each kettle and once it reaches boiling point, we time how long it continues to boil before switching itself off.
Kettles that continue to boil after the water has already reached boiling point waste energy. We've seen some that stay on for up to 30 seconds.
Overboil time accounts for 15% of the total score.
4. Minimum fill
Key question: does it allow you to boil small amounts of water?
With each kettle, we check the minimum amount of water you need each time. Kettles with a lower minimum fill help you save energy because you don't have to boil more water than you need, so we give them a higher rating. We also check that the kettle has a one-cup marker, penalising the models that make you measure out your water first.
Our Energy Saver logo highlights the kettles that save you energy. To earn an Energy Saver award, a kettle must allow you to boil small amounts of water, and it must turn off promptly after the water is boiled.
Minimum fill accounts for 15% of the total score.
5. Limescale filter
Key question: does it have a good limescale filter?
Nobody wants a collection of bitty limescale flakes in their tea. We inspect each limescale filter carefully to check it fits into the spout properly, then we pass debris through the filter to check how well it does its job. We also test how easy it is to remove, clean and replace.
Limescale filter accounts for 15% of the total score.
6. Noise
Key question: how noisy is the kettle while boiling?
We use a sound level meter to measure in decibels how loud each kettle is while boiling. Some of the loudest kettles we've tested are comparable in decibels to the noise made by an electric drill – not what you need first thing in the morning.
We also get a listening panel to rate how intrusive they think the sound is and to highlight any unusual or annoying noises.
Noise accounts for 5% of the total score.
Pick the perfect kettle with our reviews
Every kettle can boil water, but that doesn't mean they're any good. We can help you avoid shoddy kettles that are slow, noisy and leave you with bits of limescale in your tea.
See the kettles that stood out in our tough tests by heading to our kettle reviews.
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