Electricity Cost Calculator
Find out what an appliance costs to run. Enter its power in watts or kilowatts, how many hours a day it is on and your price per kilowatt-hour, and see the energy used and the cost per day, week, month and year.
Printed on the appliance label.
0 to 24.
7 if used every day.
On your electricity bill, in your currency.
Result
Enter the power, the hours of use and the price per kWh.
The calculation runs in this browser tab. Nothing you enter is uploaded, saved or logged.
How is the cost of running an appliance calculated?
Electricity is billed in kilowatt-hours (kWh). One kilowatt-hour is the energy used by a 1,000-watt appliance running for one hour. The energy an appliance uses is its power in kilowatts times the hours it runs, and the cost is that energy times the price per kWh: a 1,500 W heater on for 3 hours uses 1.5 × 3 = 4.5 kWh, which at 0.18 per kWh costs 0.81.
The power is usually printed on the appliance’s label or in its manual, in watts. Many appliances do not draw their full power all the time: a fridge or a thermostat-controlled heater switches on and off, so its average power is lower than the label. For those appliances, use the hours it is actually on, or a measured value from a plug-in energy meter.
How to use the Electricity Cost Calculator
- Enter the appliance’s power and choose watts or kilowatts.
- Enter the hours of use per day, and the days per week if it is not used every day.
- Enter your price per kWh from your bill. If you have several identical appliances, enter how many.
- Read the cost per month at the top and the table of energy and cost per day, week, month and year.
Formula
- Energy
- kWh = power in kW × hours of use
- Cost
- cost = kWh × price per kWh
- Watts to kilowatts
- kW = W ÷ 1,000
- Over time
- per week = × 7; per month = × 365 ÷ 12; per year = × 365
If an appliance is used on fewer than 7 days a week, the energy per calendar day is the energy of a day of use times days per week ÷ 7.
A month is taken as one twelfth of a 365-day year, 30.42 days.
Worked example
A 1,500 W heater on for 3 hours a day, with electricity at 0.18 per kWh. These are the results the calculator gives:
| Question | Result |
|---|---|
| Input: Power | 1500 |
| Input: Power in | Watts (W) |
| Input: Hours of use per day | 3 |
| Input: Price per kWh | 0.18 |
| Cost per month (average) | 24.64 |
| Power | 1,500 W |
| Energy per day of use | 4.50 kWh |
| Cost per year | 295.65 |
Assumptions and limits
- The label power is usually the maximum. The real average depends on the appliance, so the result is an estimate unless you measure the actual consumption.
- Standby power is not included. An appliance left plugged in uses a little power even when off, which can add up for many devices.
- The calculator uses a single flat price per kWh. If your tariff has different day and night rates, or tiers, or fixed standing charges, the real cost differs.
- Taxes and fees are included only if they are already in the price per kWh that you enter.
Frequently asked questions
How do I calculate the cost of running an appliance?
Multiply the power in kilowatts by the hours it runs to get kWh, then multiply by the price per kWh. A 100 W bulb on for 10 hours uses 1 kWh, costing one unit of your price.
What is a kilowatt-hour?
The energy used by a 1,000-watt appliance in one hour, the unit on your electricity bill. A 2,000 W kettle running for 3 minutes uses 0.1 kWh.
How do I convert watts to kilowatts?
Divide by 1,000. 1,500 W is 1.5 kW. The calculator accepts either unit.
Where do I find an appliance’s power?
On the rating label on the back or underside, or in the manual, in watts. If only volts and amps are shown, multiply them: 230 V × 6.5 A is about 1,500 W.
Why is my real bill different?
Appliances with a thermostat, such as fridges and heaters, do not run at full power all the time, and tariffs may have different rates by time of day, tiers and standing charges. Use hours of actual use, or measure with an energy meter.
How is the monthly cost calculated?
As one twelfth of the yearly cost, or the daily cost × 365 ÷ 12, about 30.42 days. The page also shows daily, weekly and yearly figures.