How appliance running costs are worked out
Electricity is billed in kilowatt hours: 1,000 watts running for one hour. So the cost of running anything comes down to three numbers you can find in minutes, its power draw in watts (on a label, in the manual, or from a plug-in energy monitor), how long it runs each day, and your tariff's unit rate in pence per kWh.
The calculator scales that to a week, a month (one twelfth of the year) and a full year. It deliberately does not assume a unit rate for you: rates differ by supplier, region and payment method, and the price cap is revised every three months, so check your own bill or app for the real figure.
Typical appliance wattages
Power ratings vary by model and age, so treat these as typical starting points and check the rating label on your own appliance. Also watch the gap between peak and average draw: many appliances only pull their headline wattage for part of the time they are on, which is why a plug-in energy monitor is the gold standard for the ones you care about.
- Kettle: 3,000 W while boiling
- Washing machine: around 2,000 W while heating the water, far less the rest of the cycle
- Electric heater: 2,000 to 3,000 W
- Fridge: around 150 W while the compressor runs, but it cycles on and off, so the average draw over a day is much lower
- Television: around 100 W for a mid-size set
- LED bulb: around 10 W
Worked examples (27p per kWh used as an example rate)
These use 27p per kWh purely to make the arithmetic concrete. Substitute your own unit rate, the shape of the answer stays the same: wattage × hours is what you pay for.
Cutting the running costs that matter
The pattern in the examples is the lesson: anything that makes heat dominates. A heater, tumble dryer or oven used daily costs hundreds of pounds a year, while LED bulbs and routers cost pounds. So the high-value habits are heat habits, boil only the water you need, wash at 30, dry clothes on a rack when you can, and never leave an electric heater running in an empty room. Remember the figures here exclude your standing charge, a fixed daily fee you pay regardless of use. For wider help with bills and efficiency, see gov.uk's energy efficiency guidance. This is guidance, not financial advice.
Frequently asked questions
What is a kilowatt hour?
A kilowatt hour (kWh) is the unit your electricity bill charges in. It is 1,000 watts running for one hour, so a 100 W television on for 10 hours and a 2,000 W heater on for 30 minutes each use exactly 1 kWh. Your unit rate is the price you pay per kWh.
Where do I find my electricity unit rate?
On a recent bill, in your supplier's app, or in your tariff details, listed as pence per kWh. Rates vary by supplier, region and payment method, and the price cap changes every three months, so check your own figure rather than using a number from the news.
Why is my bill higher than the appliance costs I calculate?
Two main reasons. Your bill includes a standing charge, a fixed daily fee of tens of pence that you pay regardless of usage, and a home runs many loads at once: fridge, router, chargers, lighting, hot water and heating. Add the standing charge and the other appliances and the gap usually closes.
Which appliances cost the most to run?
Anything whose main job is making heat: electric heaters, tumble dryers, ovens, immersion heaters, kettles and the heating phase of washing machines and dishwashers. Electronics like TVs, laptops and LED lighting are comparatively cheap even over long hours.
Do appliances use electricity on standby?
Yes. Most modern devices draw a small amount, typically from under 1 W to around 10 W each, but a home full of them adds up to a constant trickle. Switching off genuinely unused devices at the wall, or on a standby-cutting extension lead, saves a modest but real amount over a year.