Kettles: FAQs
How long does it take to boil a kettle?
Not surprisingly, the answer is – it depends on the kettle. Our Best Buys boil a litre of water in less than two and a half minutes – enough for four large cups of tea.
Of course if you’re just boiling the kettle for yourself you won’t need anywhere near that amount of water and boiling times for each kettle can vary greatly, as we found in our 2007 test.
| Kettles: Time to boil | ||
|---|---|---|
| One cup (250mls) | ||
 | Least |  47secs |
| Average | 54secs | |
| Most | 1min 11secs | |
| Two cups (500mls) | ||
 | Least | 1min 17secs |
| Average | 1min 26secs | |
| Most | 1min 47secs | |
| Four cups (1 litre) | ||
 | Least | 2mins 3secs |
| Average | 2min 34secs | |
| Most | 3mins 13secs | |
How much energy does a kettle use?
On average a kettle uses the same amount of energy to boil a litre of water as it takes to run a fridge for about seven hours, so it’s a good idea to boil only as much water as you need. The British boil their kettles on average four times a day, so you should buy a kettle that's as energy efficient as possible.
A slow boiling kettle isn’t necessarily the most inefficient one. Some kettles waste energy, continuing to boil for up to 10 seconds before the automatic cut off switches the kettle off – a period we refer to as 'overboil'.
| Kettles: Energy consumption | ||
|---|---|---|
| Boiling one litre | ||
 | Least | 0.103 kWh |
| Average | 0.114 kWh | |
| Most | 0.120 kWh | |
Manufacturers have created alternative products which aim to make it easier to save energy:
Ecokettle
The Ecokettle is fast to boil and uses less energy than all the kettles on test, although it’s not intuitive to use. It has an inner and outer chamber with three sets of water level graduations, which can be confusing at first glance, and the centre button used to transfer water between chambers is stiff to depress.
Tefal QuickCup
The Tefal QuickCup: hot water at the touch of a button
The QuickCup is more of a water heater than a kettle, but it dispenses hot water at the touch of a button, and only heats as much as you need.
We've tested this innovative product so you can decide if its features outweigh its limitations.
Do illuminated kettles use a lot more energy?
We found the LED illumination used in kettles which glow or change colour only use about 1W, which is tiny compared to the 3000W used by the heating element. Even in the few kettles that remain illuminated whilst on standby, the cost of that 1W over the course of a year is going to be less than £1.
Of course, you should think carefully about whether you really need a kettle which glows with all the colours of the rainbow.
Do I have time to make a cup of tea in the adverts?
All our Best Buy kettles boil a litre of water in less than two and a half minutes – enough for four cups of tea. That’s fairly quick, but with around three and a half minutes of adverts on terrestrial commercial channels you’ll be hard pressed to fill, boil and brew in the space of one ad break.
Watching back-to-back programmes on the BBC will leave you higher and drier with around a minute and a half between shows. But there’s still hope.
Coffee is best made with water that isn't boiling, and it takes about a minute to boil one cup's worth of water, or a minute and a half for two cups. So if you want to be back in your seat for the opening credits, switch off the kettle just before the water boils and make it an instant coffee for one.
What's the best way to boil water for coffee?
Whether you want a proper cup of coffee made in a proper copper coffee pot, or a simple instant, coffee experts agree you shouldn’t pour boiling water onto coffee. Boiling water can create a slightly bitter and burnt taste – it can even be noticeable with instant coffee, although adding milk helps to disguise it.
There’s no definitive answer as to how hot water should be to make coffee, but our expert recommends somewhere between 92 and 96 degrees celsius.
So how long should you leave the kettle once it’s boiled? We timed each of the kettles in our 2007 test to see how long freshly boiled water took to cool to 95 degrees celsius. The fastest cooled in around 78 seconds, but for most kettles you’ll need to wait between three and five minutes.
| Kettles: Boiling points | ||
|---|---|---|
| Time to boil 1 litre (4 cups) | ||
| Fastest | 2mins 3secs | |
| Average | 2mins 34secs | |
| Slowest | 3min 13secs | |
| Overboil | ||
| Fastest | Less than 1sec | |
| Average | 5secs | |
| Slowest | 12secs | |
| Time to cool to 95 degrees C | ||
| Fastest | 1min 18secs | |
| Average | 3min 55secs | |
| Slowest | 5mins 47secs | |
A faster alternative is to intercept your kettle before it’s boiled – a matter of skill and judgement with most kettles although some offer dedicated coffee settings or temperature adjustments, so there's no reason for burning your beans.
How can I judge the capacity of kettles?
Some kettles measure capacity in cups, others in litres. If you work on the premise that a mug of coffee will need the equivalent of 250ml you can’t go far wrong.
Some kettles display very few water level graduations and over half in our most recent test had no minimum level mark at all which can be frustrating. Only a few kettles have a minimum filling requirement of one cup.
Most specify filling with at least 0.5 litres or two cups-worth of water before boiling; inefficient if you’re just after a quick cup of coffee on the run.
How often should I clean it?
All manufacturers recommend cleaning and descaling your kettle to keep it in good working order. This will also ensure it remains as efficient as possible .
You can use vinegar for cleaning, but previous Which? tests found that even after rinsing repeatedly kettles can still retain an unappetising vinegary aroma.
How often you need to descale your kettle depends on how hard your water supply is, but it’s advisable to check the spout filter regularly for any build-up that can be easily cleaned off.
What about this Quooker thing I saw advertised?
For boiling water at the push-and-twist of a tap you can get your sink kitted out with a Quooker.
Available in 3 and 7 litre capacities, the insulated tank sits under your sink providing you with filtered, boiling water from your mains supply through a dedicated boiling water tap.
The boiling water is stored in the tank ready for when you need it, but if you use a whole tank full in one go you’ll have to wait around ten to 20 minutes for it to refill and boil.