How Much Does It Cost to Boil a Kettle in the UK?

Here is what an electric kettle costs per boil at 26.32p per kWh. These figures assume tap water starts at 15°C and the kettle turns 90% of the electricity into heat in the water.

Full kettle (1.7 litres): about 0.19 kWh, so about 4.9p a boil.

1 litre (about four mugs): about 0.11 kWh, so about 2.9p a boil.

One mug (250ml): about 0.027 kWh, so about 0.7p a boil. Many kettles have a minimum fill line of around two mugs, so check yours. Filling below the line is not safe.

In winter, tap water is colder, so each boil can cost up to about a tenth more. In summer it can cost a little less.

Want to work out other kitchen gadgets too? Our appliance running cost calculator works costs out from an appliance’s wattage and how long it runs. For a kettle that gives a similar answer to the sums here.

Say you make four hot drinks a day. Boiling a full kettle every time costs about 20p a day, or about £72 a year. Boiling just one mug each time costs about 2.9p a day, or about £11 a year.

Most people sit somewhere in between. The Energy Saving Trust says only filling the kettle with the water you need saves about £10 a year in Great Britain. That fits our sums for a household that overfills a bit, rather than one that fills to the top every time.

A quick way to fill the right amount: pour the mugs you are about to make into the kettle, rather than filling it from the tap and guessing.

Per litre at the price cap, a pan on a gas hob is cheapest to run, at about 2.0p, even though gas wastes most of its heat. An electric kettle costs about 2.9p, an induction hob about 3.0p and a microwave about 4.0p.

Why is gas cheaper when it is so wasteful? Gas costs 7.97p per kWh at the cap, about a third of the electricity price. In Michael de Podesta's tests, gas burners put only about 36% to 56% of their heat into the water, with bigger burners wasting more. We use 40%. Even at that rate, the cheaper fuel wins.

Gas is much slower, though, and it heats your kitchen rather than the water. It is also easy to put too much water in a pan. If you boil more than you need on the hob, the kettle quickly becomes the cheaper option.

A microwave is the most expensive way to boil a litre. In the 2022 tests it was about 65% efficient. For a single mug it costs about 1.0p, still more than a kettle boiling just that mug, and water heated in a microwave can boil over suddenly when you move it. Comparing microwaves anyway? See our best microwave UK guide.

1. Boil only what you need. This is by far the biggest saving, and it costs nothing.

2. Do not boil for green tea or coffee you then leave to cool. Heating water to 80°C instead of 100°C takes about 24% less energy, because you are warming it by 65°C rather than 85°C. Kettles with temperature settings make this easy.

3. Skip the keep-warm button unless you really need it. Keeping water hot means the kettle keeps topping up the heat it loses.

4. Make several drinks from one boil. One boil of 1 litre costs less than four separate boils of 250ml each, because the kettle body heats up once, not four times.

A basic kettle with a simple on and off switch uses no power when it has switched itself off. Kettles with a digital display, temperature settings or a keep-warm mode may use a small amount on standby, so check the manual. If you want to know for sure, plug it into an energy monitor plug and look at the reading when the kettle is off.