Electricity Cost Calculator
What an appliance actually costs to run, per hour, day, month and year.
In short
Running cost is watts ÷ 1000 × hours used × price per kWh. A 2000 W heater for three hours a day at 25p per kWh costs £1.50 a day, about £45 a month. Heating, cooling and anything that heats water dominate a bill; standby devices rarely do.
Last reviewed
Runs entirely in your browser. Nothing you type here is uploaded, stored or logged.
The calculation
cost = (watts ÷ 1000) × hours × price per kWhA kilowatt-hour is one kilowatt drawn for one hour. So a 2000 W heater uses 2 kWh per hour of running. Three hours a day at 25p per kWh is £1.50 a day, about £45 a month, or £548 a year if run all year.
That last figure is the one worth looking at. Per-hour costs are small enough to feel trivial and annual costs are not.
Finding the wattage
Look for the rating plate, usually a sticker or moulded panel on the back or underside, or inside the door on ovens and washing machines.
If it lists amps and volts instead, multiply them: 10 A at 230 V is 2300 W. If it gives a range, the higher figure is the maximum draw, which most appliances only reach intermittently.
Note that thermostatic appliances cycle. A fridge rated at 150 W does not draw 150 W continuously. The compressor runs perhaps a third of the time. For those, the annual kWh figure on the energy label is far more accurate than any calculation from wattage.
Where the money actually goes
This is the useful insight, and it's consistent across almost every household: anything that makes heat costs real money; anything that runs electronics doesn't.
| Appliance | Typical power | Roughly, per year* |
|---|---|---|
| Electric heater, 3 h/day in winter | 2000 W | £135 |
| Tumble dryer, 4 loads a week | 2500 W | £130 |
| Immersion heater, 1.5 h/day | 3000 W | £410 |
| Fridge-freezer, always on | ~150 W cycling | £70–100 |
| Oven, 1 h/day | 2100 W | £190 |
| Kettle, 5 boils a day | 3000 W | £55 |
| Desktop PC, 6 h/day | 200 W | £110 |
| Television, 4 h/day | 100 W | £37 |
| Router, always on | 10 W | £22 |
| LED bulb, 5 h/day | 9 W | £4 |
| Phone charging, daily | ~5 W for 2 h | £1 |
*At 25p per kWh. Adjust proportionally for your own rate.
Standby: real, but small
A device drawing 1 W constantly costs about £2.19 a year at 25p per kWh. Switching off every standby device in a typical home might save £20–40 across the year.
That's worth doing and it is not where your bill comes from. Ten minutes less tumble drying a week saves more than unplugging every charger in the house.
What your bill includes that this doesn't
- Standing charge: a fixed daily fee whether you use anything or not, often 50–60p a day. That's around £200 a year before you switch anything on.
- Tax: VAT or sales tax on top.
- Time-of-use rates. On an off-peak tariff, the same appliance costs very different amounts depending on when you run it, which is the whole argument for running dishwashers and washing machines overnight.
This calculator gives the marginal cost. What you save by using something less. That's the number that answers a decision, which the total bill doesn't.
Where the savings actually are
- Heating and cooling. A degree on the thermostat is worth more than every gadget in the house combined.
- Hot water. Shorter showers, and don't heat a full tank you won't use.
- Tumble drying. The single most expensive routine appliance in most homes. A clothes airer is free.
- Fill the machine. A half-empty dishwasher costs the same as a full one.
- Boil what you need. Filling a kettle for one cup wastes most of the energy.
- Shift to off-peak if your tariff has one.
Notice that none of these involve unplugging a phone charger. Effort is best spent where the kilowatt-hours actually are.
Frequently asked questions
How do I work out what an appliance costs to run?
Watts ÷ 1000 × hours used × price per kWh. A 2000 W heater running three hours a day at 25p per kWh costs £1.50 a day, roughly £45 a month. The wattage is on a label on the appliance or in its manual.
Where do I find the wattage?
On a rating plate, usually the back or underside of the appliance, or inside the door on ovens and washing machines. If only amps and volts are listed, multiply them: 10 A at 230 V is 2300 W.
Does standby actually cost anything?
Much less than people think. A device drawing 1 W constantly costs about £2 a year at 25p per kWh. Switching everything off at the wall might save £30 across a whole house, real, but nothing next to heating, hot water or a tumble dryer.
Why is my bill higher than these numbers suggest?
Because a bill also includes a standing charge, a fixed daily fee regardless of usage, plus tax, and possibly different rates at different times of day. This calculates the marginal cost of running one appliance, which is the number that answers "should I use this less".
Which appliances actually matter?
Anything that heats or cools. Electric heating, immersion heaters, tumble dryers, ovens and kettles dominate. Anything that only powers electronics, TVs, laptops, routers, phone chargers, is close to irrelevant by comparison.