Electricity Cost Calculator
Pick an appliance or enter its watts, say how long it runs and enter your rate to see the running cost in GBP per hour, day, month and year.
Formulas shown on this page · Last reviewed October 2026
How the electricity cost calculator works
kWh = watts ÷ 1,000 × hours × quantity
cost = kWh × rate per kWh
Appliance wattage is on the rating label or in the manual. Fridges and heat pumps cycle on and off, so the presets use an average draw rather than the maximum. Presets are typical for the UK, for example a 3 kW kettle or a 2 kW heater; edit the watts and hours to match your own.
Your electricity rate
The default rate is £0.26 per kWh, which is typical but only a guide. Rates vary by region, supplier and tariff, and smart or time-of-use tariffs can make overnight EV charging cheaper. The rate is quoted in pence per kWh on most bills, so divide by 100 to enter it here, and check your latest bill for the exact figure.
| Example | kWh/day | Cost/day | Cost/year |
|---|---|---|---|
| Kettle (3 kW), 0.25 h/day | 0.75 | £0.20 | £71 |
| Electric heater (2 kW), 4 h/day | 8 | £2.08 | £759 |
| EV home charger (7 kW), 3 h/day | 21 | £5.46 | £1,993 |
Supply charge
Many bills also include a daily standing charge, roughly £0.53 a day (£193 a year) at the default. It is paid whatever you use, so it is shown separately and not added to appliance costs. Heat pumps deliver several kWh of heat for each kWh of electricity, so they cost much less to run than a 2 kW resistive heater for the same warmth.
Frequently asked questions
How much does a 3 kW kettle cost to run?
Used 15 minutes a day it draws 0.75 kWh, costing about £0.20 a day or £71 a year at £0.26 per kWh.
What does a 2 kW heater cost per hour?
2 kWh × £0.26 = £0.52 per hour. Running 4 hours a day that is £2.08 a day.
How much does it cost to charge an EV at home?
A 7 kW charger running 3 hours delivers 21 kWh for about £5.46 at the default rate. Time-of-use tariffs can lower this.
How do I convert watts to kWh?
Divide the watts by 1,000 and multiply by the hours used. For example, 2,000 W for 3 hours is 2 × 3 = 6 kWh.