Electricity cost calculator
Enter an appliance’s power, how long it runs and what you pay for electricity to see what it really costs to keep it on.
Settings
Use the unit rate from your bill, which already includes VAT. Leave out the daily standing charge.
Running cost
- Per day of use
- £0.00
- Per month
- £0.00
- Energy per year
- £0.00
How the electricity cost is calculated
Energy use in kilowatt-hours (kWh) is the power in watts × hours of use ÷ 1,000. A 100 W TV used for 4 hours uses 0.4 kWh a day. Multiplying that by your unit rate per kWh gives the cost per day of use.
The yearly cost takes into account how many days a week the appliance runs, spread over the 365 days of the year. The monthly cost is a twelfth of the yearly cost.
You can find the power on the appliance’s rating plate or in its manual. Many appliances use less than their maximum power most of the time, so the result is an upper estimate. The daily standing charge on your bill is paid whether or not the appliance runs, so it does not change what running it costs.
Frequently asked questions
How do I calculate the electricity cost of an appliance?
Multiply the power in kilowatts by the hours of use and by the unit rate per kWh. A 1,500 W heater running for 3 hours costs 1.5 kW × 3 h × £0.26 = £1.17 a day.
How many kWh does an appliance use?
Divide the wattage by 1,000 and multiply by the hours it runs. A 60 W laptop used 8 hours a day uses 0.48 kWh a day – about 175 kWh a year if it is used every day.
What electricity price should I use?
Use the unit rate per kWh from your electricity bill or your supplier’s app; it already includes VAT. On a time-of-use tariff, use the rate for the hours the appliance runs.
Does standby use electricity?
Yes, many appliances draw a few watts on standby. Enter the standby power and 24 hours a day to see what it costs over a year.