Electricity Cost Calculator
Electricity cost = (Wattage ÷ 1,000) × Hours used × Electricity rate per kWh. A 2,000W appliance running for 1 hour at 24.5p/kWh costs about 49p.
How much does it cost to run your appliances? Whether it is a tumble dryer, an electric heater, or a gaming PC, this calculator shows you the running cost per hour, day, week, month, and year.
Enter the wattage (usually on the appliance label), how long you use it, and your electricity rate to get an instant cost breakdown.
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What this calculator does
This calculator converts an appliance’s wattage into kWh energy usage, then multiplies by your electricity unit rate to show the running cost across different time periods.
Who it is for
Homeowners and renters who want to understand which appliances cost the most to run, anyone trying to reduce energy bills, or people comparing the cost of different appliances before buying.
How to use it
Enter the appliance wattage (check the label or manual), hours used per day, and days per week. The electricity rate defaults to the UK average but you can adjust it to match your tariff. Click 'See My Result' for a full cost breakdown.
How the calculation works
kW = Watts ÷ 1,000. kWh per day = kW × hours used. Daily cost = kWh × unit rate. Weekly = daily × days per week. Monthly = weekly × 4.33. Annual = weekly × 52.
Worked example
A 2,000W electric heater used for 4 hours per day, 5 days per week, at 24.5p/kWh: kW = 2. kWh/day = 8. Daily cost = 8 × 24.5p = £1.96. Weekly = £9.80. Monthly = £42.43. Annual = £509.60.
Assumptions and limitations
- Assumes constant wattage during operation (actual usage may vary with settings, load, or cycles)
- Default electricity rate uses the UK Ofgem price cap rate — your actual rate may differ
- Does not account for standby power consumption
- Monthly cost uses 4.33 weeks per month (52 ÷ 12)
- Actual costs may vary with time-of-use tariffs, seasonal usage patterns, and appliance efficiency
Frequently asked questions
How much does an appliance cost to run?
It depends on the wattage, how long you use it, and your electricity rate. For example, a 100W lightbulb running 8 hours a day at 24.5p/kWh costs about 19.6p per day (£71.54/year).
How do I calculate electricity cost from watts?
Divide the wattage by 1,000 to get kW. Multiply by hours used to get kWh. Multiply by your electricity rate (in pence per kWh) to get the cost in pence.
What does kWh mean on my bill?
kWh stands for kilowatt-hour. It is the standard unit of energy your supplier charges for. One kWh is the energy used by a 1,000W appliance running for one hour.
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Sources and references
Ofgem price cap rates (https://www.ofgem.gov.uk/check-if-energy-price-cap-affects-you), Energy Saving Trust appliance running costs (https://energysavingtrust.org.uk/)
Last updated
Last reviewed: 2026-04-12.