Kettles: How we test kettles
We put each kettle through a number of tests in the Which? lab and only the kettles that score highest overall can become Best Buys.
Speed of boiling
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 kettles, 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.
Kettles which can boil a litre in less than two-and-a-half minutes get a five-star rating for time to boil.
Kettle energy use
For each kettle, we check what the minimum amount of water is that you need to put in. 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 calculate the average amount of energy used by each kettle to boil a litre of water, though this typically varies very little between kettles.
Kettles in general don't use much energy - boiling one litre of water twice a day would cost you an average of just £11.86 per year in electricity.
We boil a litre of water in each kettle and once it reaches its average boiling temperature, we time how long the kettle continues to boil before switching itself off.
We can then work out how much extra energy the kettle uses when it continues to boil before automatically switching off.
We measure noise levels whilst each kettle is boiling, and also get a listening panel to rate how intrusive the noise is.
Ease of use
Our expert panel pour 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 also look at the water gauge on each kettle - kettles with large windows on either side, allowing you to see how much water is in the kettle, get the highest marks in this area.
Ease of cleaning
We check whether the body of the kettles shows finger marks easily, how easy these are to remove, and how easy it is to clean the inside of the kettle.
We also note any features which might make life easier, such as long cords, cool-touch bodies and wide-opening lids.
Our testers inspect each limescale filter to check if it is well-fitting, durable, effective and easy to remove, clean, and replace.
Kettle test scores
Our total test scores ignore price and are based on:
- Performance (time to boil, energy consumption, overboil time and minimum fill) - 50%
- Limescale filter - 10%
- Noise - 10%
- Ease of use - 25%
- Build quality - 5%
Kettles must score 74% or more overall to become a Which? Best Buy.