Appliance wattage, how long it runs and your unit price → what it actually costs you per day, month and year.
This is unit cost only — it does not include your daily standing charge.
About this calculator
The calculation is simply cost = power (kW) × hours × unit price. Wattage is converted to kilowatts by dividing by 1,000, so a 2,000 W appliance is 2 kW; run for one hour it uses 2 kWh, and at 25p per kWh that costs 50p.
Your usage period sets how often that run happens. The figures are put on a common basis of 365 days in a year, with a week as exactly 7 days and a month as one twelfth of the year, so the daily, weekly, monthly and yearly costs are all consistent with each other rather than drifting apart.
The unit price is entered in the minor unit — pence per kWh in the UK, and the equivalent hundredth of the main unit for other currencies. That matches how electricity tariffs are normally advertised.
Real bills are higher than this figure, for two reasons. There is a daily standing charge that you pay regardless of how much you use, which this calculator deliberately excludes, and in the UK domestic energy also carries 5% VAT, which may or may not already be included in the rate you enter. Appliances with a thermostat — fridges, freezers, heaters, kettles — also cycle on and off rather than drawing full power continuously, so use realistic running hours rather than the time they are switched on.
Frequently asked questions
How do I work out an appliance's wattage?
It is usually printed on a label on the back or base of the appliance, or in the manual, given in watts (W) or kilowatts (kW). A typical kettle is around 3,000 W, a washing machine 2,000 W and a fridge 100–200 W while the compressor is running.
Why is my actual bill higher than this?
Because a bill also includes a daily standing charge you pay whatever you use, and in the UK 5% VAT on top. This calculator covers only the unit cost of the electricity that appliance consumes.
Does a thermostat-controlled appliance really run for all those hours?
No. Fridges, freezers and heaters cycle on and off to hold a temperature, so they draw full power for only part of the time they are switched on. Estimate actual running time rather than plugged-in time, or the yearly figure will be well over the truth.