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Updated: 14 Mar 2022

How we test kettles

Buying a new electric kettle? Find out how our in-depth kettle testing helps you to get the best kettle for your kitchen.
Rebecca Jakeman

Our independent kettle reviews tell you everything you need to know about a kettle before you buy it. What's more, they allow you to compare models on an even footing, as we test each kettle in exactly the same way.

Every kettle can boil water, but that doesn't mean they are any good. We can help you avoid shoddy kettles that are slow, noisy and will leave you with bits of limescale in your tea. 

Our reviews answer the most crucial questions about kettles: 

  • How quickly does it boil?
  • How noisy is the kettle while boiling?
  • Does it waste energy by over-boiling?
  • Does it allow you to boil small amounts of water?
  • Does it have a good limescale filter?
  • Is the kettle easy to use?
  • Should I buy it?

Read on to find out how we test kettles to ensure our Best Buys are a fast, fuss-free route to a lovely brew.

See the kettles that stood out in our tough tests by heading to our kettle reviews.

How quickly does it boil?

We fill each kettle with one litre 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 the kettle automatically switched itself off and how long it took. We test each kettle three times to find an average boiling time and temperature.

The fastest kettles can boil a litre in less than two minutes and 18 seconds, but we've also tested kettles that take nearly twice as long - leaving you waiting around for your cuppa.

How noisy is the kettle while boiling?

We use a sound level meter to measure how loud each kettle is in decibels 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 the noise of each kettle is, to highlight any unusual or annoying noises.

Does it waste energy by over-boiling?

We boil a litre of water in each kettle and, once it reaches boiling point, we time how long the kettle 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 kettles that stay on for an extra 30 seconds.

Does it allow you to boil small amounts of water?

For each kettle, we check what the minimum amount of water is that you need to use 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 are best at helping you save 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.

Does it have a good limescale filter?

Nobody wants a collection of bitty limescale flakes in their tea. We carefully inspect each limescale filter to check that it fits into the spout properly, then we pass debris through the filter to check how well it does its job. We also look at how easy it is to remove, clean and replace.

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 in order 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 - allowing you to see how much water is in the kettle - get the highest marks in this area.

We also check whether the kettle shows finger marks easily, how easy these are to remove and how easy it is to clean the inside of the kettle.

What is a Which? Eco Buy kettle?

If you're trying to make more environmentally-friendly choices when buying your next kettle, be sure to look out for our new Eco Buy badge.

Eco Buy kettles are a more sustainable option compared to other kettles, meaning they'll help you to cut down on 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 73%
  • Five stars for speed of boiling
  • A minimum fill equal to or smaller than 275ml
  • An overboil time of less than five seconds
  • Its brand must get a good longevity rating in our annual consumer surveys

Less 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.

Should I buy it?

The tests above all form part of the overall score for each kettle we review. When working out that overall score, we give more emphasis to the tests that we know are more important to you, including speed, energy efficiency and ease of use:

  • 30% ease of use
  • 20% speed
  • 15% overboil time
  • 15% minimum fill
  • 15% limescale filter
  • 5% noise

Kettles with an overall score of 73% or above are rated as Best Buys, while those scoring 45% or below are Don't Buys - kettles that did so poorly in our testing that we think they are best avoided.