Electricity cost calculator
Enter an appliance's wattage, how long it runs and your price per kWh. You get the energy used and the running cost straight away. The rate is pre-filled with the UK Ofgem cap average of 26.32p/kWh. Pick another currency and type your own rate if you're elsewhere.
Prices last checked: 26 September 2026 · Source: Ofgem energy price cap, 1 October to 31 December 2026 · Great Britain average, standard variable tariff, paid by Direct Debit
The electricity cost formula
Power is shown in watts (W). Bills charge for energy in kilowatt-hours (kWh). Convert watts to kilowatts, multiply by time, then multiply by the price:
Cost: kWh × price per kWh = usage cost
Worked examples at UK prices
All at the Ofgem cap unit rate of 26.32p/kWh for 1 October to 31 December 2026:
- A 1,000W appliance for 2 hours: 1,000 ÷ 1,000 × 2 = 2 kWh. 2 × 26.32p = 53p. Every day for 30 days: 60 kWh, £15.79.
- A 2kW heater for 4 hours an evening: 8 kWh, £2.11 a night if the element never cycles off. See the heater calculator for the thermostat effect.
- A 60W laptop and monitor, 8 hours a day: 0.48 kWh, 13p a day, £3.79 a month.
- A 9.5kW electric shower for 8 minutes: 9.5 × 8 ÷ 60 = 1.27 kWh, 33p per shower.
Example monthly costs by appliance
| Appliance | Example power | Example use | kWh per month | Monthly cost (UK cap) |
|---|---|---|---|---|
| Fridge freezer | 250 kWh/year label | Always on | 20.8 | £5.48 |
| Electric heater (winter) | 2,000 W | 4 h/day | 240 | £63.17 |
| Washing machine | 1 kWh per wash | 4 washes/week | 17.3 | £4.56 |
| Gaming PC | 450 W | 3 h/day | 40.5 | £10.66 |
| Air fryer | 1,500 W at 70% | 20 min, 5 times/week | 7.6 | £2.00 |
| TV | 100 W | 5 h/day | 15 | £3.95 |
More appliances: UK appliance running costs covers 19 of them, from the kettle to EV charging.
What this estimate does not include
Electricity bills also contain fixed charges: the UK daily standing charge (54.83p a day at the cap), the French abonnement, network fees and taxes in other countries. Those don't change when one appliance is switched on or off, so they are outside an appliance-level estimate. The UK electricity price page shows how the standing charge adds up over a month.
Getting a better number
- Measure instead of guessing. A plug-in energy monitor shows the kWh an appliance really uses, including thermostat cycling and standby.
- Use the label. Fridges, washing machines, dishwashers and TVs have energy labels that state kWh per year, per 100 cycles or per 1,000 hours. Those are better than rated watts.
- Remember cycling. Heaters, ovens, fridges and irons switch their elements on and off. Rated watts × hours is then an upper limit.
- Match the rate to the time. On Economy 7, EV or other time-of-use tariffs, use the rate for the hours the appliance runs. The time-of-use calculator helps.
Using this calculator for a whole home
Run the calculator once for each large appliance and add the results. Long-running loads (a fridge freezer, heating, a tumble dryer, an electric shower) usually matter far more than short bursts from a kettle or toaster. The whole-home energy budget does this in one go.
Frequently asked questions
How do I calculate the cost of electricity?
Divide the watts by 1,000, multiply by the hours to get kWh, then multiply by your price per kWh. 1,500W for 2 hours is 3 kWh, which costs 79p at the UK cap rate.
What if my appliance changes power while running?
Use its average measured power, or the kWh measured over a typical session. The maximum rating is a conservative upper bound.
Is 1,000 watts the same as 1 kWh?
No. 1,000 watts is power. A 1,000W appliance running for one hour uses 1 kWh of energy. The watts to kWh converter does this for any time period.
Can I use this with euros or other currencies?
Yes. Choose the currency and enter your own price per kWh. The maths doesn't depend on the currency.
Why doesn't my bill match the calculator?
Your bill covers every appliance in the home plus fixed charges. The calculator prices one appliance's usage.