Find what an appliance costs to run. This free electricity cost calculator turns power, daily hours and your rate per kWh into the energy used and the cost per day, week, month and year.
Enter the appliance’s power (check its label – W or kW), how many hours a day it runs, and your electricity rate per kWh (on your bill). Results update instantly.
Cost = power in kW x hours x rate. A 1500 W heater for 3 hours a day at $0.15/kWh costs about $0.68 a day. Monthly figures assume ~30.4 days; yearly assumes 365.
How the Electricity Cost Calculator Works
This tool turns an appliance’s power draw, daily runtime and your electricity rate into a running cost, so you can see what a heater, appliance or device actually adds to your bill.
Formula: Power in kW = Watts ÷ 1000 (or entered directly in kW). Energy per day (kWh) = Power (kW) × Hours per day. Cost per day = Energy per day × Rate per kWh. Cost per week = Cost per day × 7. Cost per month = Cost per day × 30.4368 (average days per month). Cost per year = Cost per day × 365.
- Power — the appliance’s power draw, entered in Watts or kW (check the appliance label or nameplate)
- Unit — the toggle that tells the calculator whether Power is in Watts or kW
- Hours used per day — how many hours a day the appliance actually runs, up to 24
- Electricity rate — your cost per kWh, taken from your electricity bill
Example Scenarios
| Power | Hours/day | Rate ($/kWh) | Cost per month |
|---|---|---|---|
| 1500 W | 3 | 0.15 | $20.54 |
| 100 W | 10 | 0.12 | $3.65 |
| 2000 W | 2 | 0.20 | $24.35 |
| 60 W | 8 | 0.15 | $2.19 |
| 5 kW | 1 | 0.18 | $27.39 |
| 3000 W | 4 | 0.10 | $36.52 |
How to Get Realistic Numbers from an Electricity Cost Calculator
An electricity cost calculator is only as good as the wattage and hours you give it, and both are easy to overstate.
- The label or nameplate wattage is usually the maximum draw. Fridges and air conditioners cycle on and off, so their average draw is lower.
- Appliances with a thermostat, such as heaters, kettles and ovens, run at full power only part of the time.
- Standby loads add up. A plug-in energy monitor shows real consumption, which you can then enter into the electricity cost calculator as watts.
- Use the price per kWh from a recent bill. Many tariffs also add a fixed daily standing charge that the electricity cost calculator leaves out, because you pay it whatever you run.
If you are on a time-of-use tariff, run the electricity cost calculator twice, once at the peak rate and once off-peak, to see what shifting a dishwasher or overnight EV charge would save.
Remember that 1 kWh is 1,000 watts running for one hour. The kilowatt-hour article on Wikipedia explains the unit that your bill and the electricity cost calculator both use.
Electricity Cost Calculator FAQ
How do I find my appliance’s power in Watts?
Check the nameplate or label on the appliance itself, usually on the back, bottom or power cord — it’s often printed as “W” or “watts.” Some appliances list amps and volts instead; multiplying amps × volts gives an approximate wattage to enter.Where do I find my electricity rate per kWh?
Your electricity bill or utility account portal lists a rate per kWh (sometimes called the “energy charge” or “supply rate”). If your bill shows tiered or time-of-use rates, use the rate that applies to when you typically run the appliance.What’s the difference between entering Watts and kW?
They’re the same unit at different scales — 1000 Watts equals 1 kilowatt (kW). Use whichever matches your appliance’s label; the calculator converts Watts to kW internally before working out energy and cost, so the result is identical either way.Why does the monthly cost use 30.4368 instead of 30 days?
30.4368 is the average number of days per month across a full year (365 ÷ 12), which gives a more consistent monthly figure than assuming every month has exactly 30 or 31 days.Does this include standby power when the appliance is off?
No — it only calculates cost for the hours per day you enter as active use. Many appliances draw a small amount of standby (phantom) power when switched off but still plugged in, which this calculator doesn’t add automatically.Can I use this to compare two appliances’ running costs?
Yes — run the calculator once per appliance with its own power, hours and rate, then compare the cost-per-day or cost-per-month figures side by side to see which one costs more to run.Related Calculators
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