WiseCalcs

Electricity cost calculator

Enter the device's power in watts, how many hours it runs each day, and your price per kilowatt-hour. The calculator shows the daily, monthly, and yearly cost as you type.

Use it to see what any appliance costs to run, from its wattage and your electricity price.

W
h
USD

Monthly cost

$4.50

Daily cost
$0.15
Yearly cost
$54.75
Energy per year
182.5 kWh

The result updates as you type. It shows the cost per day, per month, and per year, plus the energy the device uses over a year.

How does it work?

Watts are divided by 1,000 to get kilowatts. A month is 30 days and a year is 365 days. You supply the price per kWh from your bill.

Electricity cost formula

cost=W1000×h×price\text{cost} = \frac{W}{1000}\times h \times \text{price}
W
Power draw in watts.
h
Hours used per day.
price
Price per kilowatt-hour.

A 100 W device run 5 hours a day uses 0.5 kWh daily; at 0.30 per kWh that is 0.15 a day, about 4.50 a month and 54.75 a year.

Method & sources

Power is entered in watts and converted to kilowatts by dividing by 1,000. The device runs the same number of hours every day. A month is treated as 30 days and a year as 365 days.

Sources

Where this method comes from — use these references to understand the formula, assumptions, and limits.

How we calculate

  • Power is entered in watts and converted to kilowatts by dividing by 1,000.
  • The device runs the same number of hours every day.
  • A month is treated as 30 days and a year as 365 days.
  • The price per kWh is the all-in rate you supply from your bill.
  • Standing charges, tiered tariffs, taxes, and standby draw are not modelled.

Rounding

Costs are rounded to two decimals and energy to one decimal for display. The calculation uses full precision.

What this calculator does

Electricity is billed per kilowatt-hour (kWh) — running one kilowatt for one hour. This calculator turns an appliance's wattage and daily run time into kilowatt-hours, multiplies by your price, and shows what it costs over a day, a month, and a year.

How to use it

  1. Enter the device's power in watts (check the label or specifications).
  2. Enter how many hours it runs per day.
  3. Enter your price per kWh from your electricity bill.
  4. Read the daily, monthly, and yearly cost below.

A worked example

A 100 W device run 5 hours a day uses 0.5 kWh daily. At 0.30 per kWh that is 0.15 a day — about 4.50 a month and 54.75 a year, using around 182.5 kWh over the year.

Finding the wattage and price

The wattage is usually on a label or in the manual. The price per kWh is on your electricity bill; use the all-in unit rate. If a device lists amps and volts, watts are amps times volts.

Common mistakes

  • Entering kilowatts in the watts field. A 2 kW heater is 2,000 W.
  • Using more than 24 hours a day. The field is capped at 24.
  • Forgetting that standby power and standing charges are not included.

When it's useful

Comparing the running cost of appliances, deciding whether an upgrade pays off, or checking what an always-on device adds to your bill.

FAQ

How is the cost calculated?
Watts are divided by 1,000 to get kilowatts, multiplied by the hours per day to get kWh, then multiplied by your price per kWh for the daily cost. Monthly and yearly figures use 30 and 365 days.
Where do I find the price per kWh?
It is on your electricity bill, usually as a unit rate. Use the all-in rate including any per-kWh charges for the most accurate result.
Does this include standing charges?
No. It only covers the energy the device uses. Fixed daily standing charges and taxes are billed separately.
How do I convert amps to watts?
Multiply amps by volts. For example, 2 amps at 230 volts is 460 watts.
Which currency does it use?
The currency follows the site language. The energy math is identical in every market.
Can I share a calculation?
Yes. Use Share to copy a link that reopens the calculator with the same power, hours, and price.

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<iframe src="https://wisecalcs.com/embed/en/electricity-cost-calculator" width="100%" height="520" style="border:0" loading="lazy"></iframe> <p>Calculator from <a href="https://wisecalcs.com/en/finance/electricity-cost-calculator">WiseCalcs</a></p>