Almost every electric kettle turns 80 to 90 per cent of the electricity it draws into heat in the water, and the differences between models are small. There is no such thing as a kettle that boils the same water for meaningfully less energy than another.
What varies enormously is how much water you boil. That is where the money is, and it is a habit rather than a purchase. A kettle can help the habit, which is the honest case for buying carefully, and it is a much smaller claim than the one usually made.
The physics, in one line
Heating water takes a fixed amount of energy. Raising one litre from cold tap temperature to boiling needs about 0.1 kWh, and no kettle can beat that, because it is set by the water, not the appliance.
So the arithmetic is simple. Multiply the litres you boil by 0.1, then by your electricity rate.
| What you boil | Energy | Cost at 25p per kWh |
|---|---|---|
| One mug, 250 ml | 0.025 kWh | About 0.6p |
| Two mugs, 500 ml | 0.05 kWh | About 1.3p |
| A teapot, 1 litre | 0.1 kWh | About 2.5p |
| A full 1.7 litre kettle | 0.17 kWh | About 4.3p |
25p per kWh is a round figure used here for the arithmetic, not a quoted tariff. Put your own unit rate in from your bill, and see how much it costs to boil a kettle for the fuller costing.
Where the waste actually is
Filling a 1.7 litre kettle to make one mug of tea wastes about 0.145 kWh, or roughly 3.6p, every time. Do that four times a day and it is about 14p a day, which is somewhere near £50 a year spent heating water you pour down the sink.
That single habit dwarfs every other efficiency consideration on this page. Nothing about the kettle you buy will save you £50 a year. Filling it properly will.
The four real sources of waste, in order of how much they cost:
- Overfilling. By a wide margin the biggest. Around £50 a year for a typical household.
- Reboiling. Water that has cooled and gets boiled again is paying twice for the same cup. It also makes worse tea, for the reasons in how to make a proper cup of tea.
- Limescale. A furred element has to push heat through an insulating layer, so it runs longer for the same boil. In a hard water area this is a real and growing cost.
- Keep-warm functions. Holding water hot for an hour to save one reboil usually costs more than the reboil would have.
Does wattage matter?
Not for energy used, and slightly for energy wasted.
A 3000W kettle and a 2200W kettle heating the same litre of water use almost the same total energy. The 3000W one gets there faster, drawing more power for less time. The energy is the same because the water needs what it needs.
The marginal difference is standing loss: a faster boil spends less time radiating heat into the kitchen, so very slightly less is wasted. It is a small effect, worth perhaps one or two per cent, and it is not a reason to choose a kettle on wattage alone. Speed is a convenience argument, which is a perfectly good argument, and we set out what wattage really buys you in wattage explained.
What to look for, if you are buying
Given the efficiency is a wash, the features worth paying for are the ones that make it easy to boil less.
| Feature | Does it save energy? |
|---|---|
| A water window you can actually read | Yes, indirectly, and it is the most useful feature here. If you cannot see the level you will overfill. |
| Cup markings, not just MIN and MAX | Yes. Filling to a marked two cups is far more accurate than guessing. |
| A low minimum fill | Yes. A kettle with a 500 ml minimum forces you to boil two cups for one. |
| Concealed flat element | Indirectly. Easier to descale, so it stays efficient. Also quieter. |
| Removable washable filter | Indirectly. Keeps scale out of the cup and makes maintenance likelier. |
| Variable temperature | Yes, a little, if you drink green tea. Heating to 80C instead of 100C uses around a quarter less energy. |
| Keep-warm | Usually no. It costs more than it saves unless it genuinely replaces a reboil. |
| App connectivity | No. |
| An eco or energy-saving badge | Almost never. There is no UK energy label for kettles, so the claim is unregulated. |
That last row is worth dwelling on. Kettles are not covered by the UK energy labelling scheme that applies to fridges and washing machines, so an eco badge on a kettle box means whatever the manufacturer wants it to mean. Treat it as marketing.
One cup kettles and hot water taps
One cup kettles dispense a measured cup on demand and genuinely do stop overfilling. They are slower per cup, they hold a reservoir of standing water, and they cost more. Whether they are worth it depends entirely on whether you would otherwise overfill, which we went into in are one cup kettles worth it.
Instant hot water taps are efficient per cup but keep a tank at temperature around the clock. For a household that makes a lot of hot drinks they can work out well. For two people and four cups a day they will not repay the installation cost in any reasonable timeframe.
A kettle beats a microwave and a hob for heating water, comfortably. A microwave heats unevenly and loses energy to the air and the container; a hob loses a great deal around the sides of the pan. If you are heating water to drink, the kettle is the efficient appliance.
Descaling is an efficiency job, not just a cleaning one
Limescale is a thermal insulator. A layer on the element means the element has to run hotter and longer to get the same heat into the water, so every boil costs slightly more, and the gap widens as the scale thickens.
In a hard water area, descaling every one to three months keeps the kettle close to its original efficiency and roughly doubles its working life. The method is in how to descale a kettle, and which descaler to use is compared in kettle descaler, vinegar or citric acid.
Six habits that actually cut the bill
- Fill to the number of cups you are making, using the markings rather than your judgement.
- Do not reboil. Tip it out and refill with fresh cold water, which is better tea anyway.
- Measure with the mug if the markings are hard to read. Fill the mug, pour it in, boil that.
- Descale on a schedule, not when it looks bad.
- Boil once for a round of drinks rather than separately for each.
- Do not use keep-warm as a default. Switch it on only when you know you will want more within the hour.
Where we stand
The Toastley 1.7L electric kettle is not sold as an eco kettle, because we do not think that claim means anything on a kettle. It is a 2200W rapid boil kettle with a concealed element, a washable limescale filter, and a water window with cup markings that you can read at a glance in a normal kitchen.
That last part is the only feature on this page that will genuinely change your bill, and it does so by making it obvious when you are about to boil four cups for one. The rest of the range is in our kettle collection, and it pairs with a matching toaster in the kettle and toaster sets.
If you want the broader buying advice rather than the efficiency question alone, that is in the best kettle for a UK kitchen.
Common questions
Are some kettles more energy efficient than others?
Only marginally. Almost all electric kettles convert 80 to 90 per cent of the electricity they draw into heat in the water, and the spread between models is small. How much water you boil matters far more than which kettle boils it.
How much does it cost to boil a kettle?
Around 0.1 kWh per litre. A full 1.7 litre kettle is roughly 0.17 kWh, which is about 4.3p at 25p per kWh. A single mug is closer to 0.6p.
Does a higher wattage kettle use more electricity?
No, not meaningfully. A 3000W kettle draws more power for less time and uses almost the same total energy as a 2200W one. A faster boil wastes very slightly less heat to the room.
Is it cheaper to boil water in a kettle or a microwave?
The kettle, comfortably. A microwave heats unevenly and loses energy to the container and the air, and a hob loses a great deal around the sides of the pan.
Does limescale make a kettle use more electricity?
Yes. Limescale insulates the element, so it has to run longer to put the same heat into the water. The effect grows as the scale thickens, which is why descaling is an efficiency job as well as a cleaning one.
Do eco kettles actually save energy?
Rarely in any measurable way. Kettles are not covered by the UK energy labelling scheme, so an eco badge is an unregulated marketing claim. A readable water window that stops you overfilling saves far more.