Electricity Cost Calculator
What an appliance costs to run per day, month and year.
Good to know. A 2,000 W heater running for an hour uses 2 kWh. Watts times hours, divided by 1,000.
How it works
In plain words
Turn watts into kilowatts by dividing by 1,000. Multiply by the hours of use to get kilowatt-hours (kWh), the unit on your bill. Multiply by your price per kWh.
The formula
kWh per day = watts ÷ 1,000 × hours × number cost per day = kWh × price per kWh per month = per day × 365 ÷ 12
Worked example
A 2,000 W heater used 3 hours a day uses 2 × 3 = 6 kWh. At 0.25 per kWh, that costs 1.50 a day, or about 547.50 a year.
Sources
No outside data or rates: this is plain arithmetic.
4 automated tests check its answers on every change.
About the electricity cost calculator
Every electrical appliance has a power rating in watts (W) or kilowatts (kW), usually on a label on the back or bottom, or in the manual. Your electricity is billed in kilowatt-hours (kWh): one kilowatt running for one hour. Put those together with your price per kWh and you have the running cost.
The rated power is the maximum. Many appliances use much less most of the time. A fridge’s compressor switches on and off, so it might average a third of its rating. A heater on a thermostat cycles too. A TV uses less at lower brightness. For the most accurate figures, a plug-in energy monitor measures actual use over a day or a week.
Heating and cooling are usually the biggest users: electric heaters, tumble dryers, kettles, ovens and air conditioners draw one to three kilowatts. Chargers, LED bulbs and routers use only a few watts each, but things that are on around the clock add up over a year.
Standby power is worth checking too. A device drawing 5 W all day, every day, uses about 44 kWh a year.
Enter the price from your own bill, since it varies a lot by country and tariff.
Questions people ask
How do I calculate the cost of running an appliance?
Divide the watts by 1,000, multiply by the hours of use, then by your price per kWh. 2,000 W for 3 hours at 0.25/kWh costs 1.50.
What is a kWh?
A kilowatt-hour: the energy used by a 1,000-watt appliance running for one hour. It is the unit on your electricity bill.
Does an appliance always use its rated wattage?
No. The rating is usually the maximum. Fridges, heaters and air conditioners cycle on and off, so their average use is lower.