What an appliance costs to run is arithmetic, not an opinion, and the arithmetic is simple enough to do yourself. Most published figures are wrong not because the sums are hard but because they use a unit rate from whenever the article was written.
The calculation
To use it you need two numbers.
- The appliance's power in kilowatts. It is on the rating plate, usually on the back or
inside the door, in watts. Divide by 1,000. A 2,200W kettle is 2.2kW.
- Your unit rate in pence per kWh. It is on your bill, not on a comparison site. If you
are on a standard variable tariff it moves with the price cap; if you are on a fixed tariff or Economy 7 it does not, and Economy 7 has two rates.
A 2.2kW kettle boiling for three minutes uses 2.2 x 0.05 = 0.11kWh. At a rate of 25p that is about 2.75p a boil. Ten boils a day is roughly £10 a month.
Why most figures you read are wrong
- They use an out-of-date rate. The cap changes quarterly. An article from two years ago
is arithmetic on a number that no longer exists.
- They assume your usage. "Cost to run a tumble dryer" depends entirely on how many loads
and on which programme.
- They quote the maximum rating. A washing machine draws its full power only while heating
the water, which is a fraction of the cycle. Fridges and freezers cycle on and off. For anything that does not run flat out, the rating plate overstates the real cost.
Where the money actually goes
The rule of thumb that survives every tariff change: anything whose job is to make heat is expensive, and everything else is not. Kettles, ovens, tumble dryers, immersion heaters and electric heaters all convert electricity directly into heat, and heat costs. A television, a laptop or a phone charger left on will not move your bill noticeably however guilty the advice makes you feel.
That is why the savings that work are about heat: washing at a lower temperature, drying outdoors, filling the kettle only as far as you need, and running the oven for one thing rather than three times in an evening.
What is coming here
We are building a calculator and a page for each common appliance, worked from the current price cap and the manufacturers' own published ratings, with the rate and the date shown on the page so you can check it. Where a figure changes because the cap changed, the page will say so rather than quietly updating.