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Electricity Cost Calculator

Work out what any device costs to run from its wattage, the hours it runs, and your price per kWh.

Device

Calculated in your browser as you type. Nothing is uploaded.

Days used per week

How many days a week the device runs. Monthly and yearly figures scale to match.

Running cost
$32.87
Estimated cost per year, about 109.6 kWh
Per day
$0.09
0.3 kWh
Per month
$2.74
9.13 kWh
Per year
$32.87
109.6 kWh

Assumes the device draws its rated wattage while running. A month is treated as 30.4 days and a year as 365.25 days.

How to calculate electricity cost

  1. Enter the device power

    Type the wattage from the device label or its spec sheet into the watts field.

  2. Add the hours and price

    Set how many hours a day it runs and the price per kilowatt-hour from your electricity bill.

  3. Adjust the days per week

    If the device does not run every day, pick how many days a week it is used.

  4. Read the daily, monthly, and yearly cost

    The energy in kWh and the running cost for each period appear instantly in the results grid.

Why use this tool

Daily, monthly, and yearly breakdown

One device turns into a full grid: the energy in kilowatt-hours and the cost for a day, a month, and a year, all updating as you type.

Handles part-time use

Set how many days a week the device actually runs and the monthly and yearly totals scale to match, so a twice-weekly appliance is not billed as if it ran every day.

Works in any currency

Type the price per kWh in your own currency and pick a symbol. The calculator works in plain numbers and never assumes dollars.

Sensible rounding

Small daily costs keep enough decimal places to stay meaningful, while yearly totals round to something you can read at a glance.

Runs entirely in your browser

Everything is calculated on your device as you type. Nothing is uploaded and there is no signup.

About this tool

Every electrical device has a power rating in watts. Multiply that by the hours it runs and you get energy, measured in kilowatt-hours (kWh), which is the unit your electricity bill charges for. This calculator does the arithmetic for you: enter the wattage printed on the device or its label, how many hours a day it runs, and the price per kWh from your latest bill, and it shows the energy used and the money spent per day, per month, and per year.

The yearly figure is usually the eye-opener. A 100 W device left on around the clock draws about 876 kWh a year; at 30 cents per kWh that is roughly 263 in running cost, more than most people guess. Halving the hours, or swapping to a lower-wattage model, moves that number in direct proportion, so the calculator is a quick way to compare two appliances or decide whether something is worth leaving on. Use the days-per-week control for anything that does not run daily, like a dishwasher or a heater, and the monthly and yearly totals scale to match.

Enter watts and the price per kWh in whatever currency you use; the tool works in plain numbers and just adds your chosen symbol. Everything is calculated in your browser as you type, and nothing is uploaded. To convert a power or energy figure between units, try the unit converter, and to see how a tariff increase changes the total, the percentage calculator handles one-off percentage changes.

Frequently asked questions

How is electricity cost calculated?
Power in watts divided by 1000 gives kilowatts; multiplied by the hours it runs gives energy in kilowatt-hours (kWh). Multiplying that by your price per kWh gives the cost. The calculator does this for a day, a month (about 30.4 days), and a year (365.25 days).
What if the device is not used every day?
Set the days-per-week control to how often it runs. The per-day figure becomes an average across the week, and the monthly and yearly totals scale down accordingly, so occasional appliances are not overcounted.
Where do I find the wattage and the price?
The wattage is usually printed on a label on the device or in its manual. The price per kWh, sometimes called the unit rate, is on your electricity bill. Enter the price in whatever currency you are billed in.
Does it account for standby power?
No. It assumes the device draws its rated wattage only while running. Many appliances also use a small amount on standby; to include that, run a second calculation with the standby wattage and 24 hours a day.
Which currency does it use?
None in particular. It works in plain numbers and adds the symbol you choose, so the result is in whatever currency you entered the price in.
Is my data uploaded anywhere?
No. Everything runs in your browser; nothing is sent to a server.

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