Electricity Cost Calculator: Appliance Running Cost

Calculate yearly electricity use and cost from watts, hours of use and your electricity rate. Compare running costs with standby consumption.

Last updated: October 3, 2026

Example: the calculation with the default values

Fields with a source carry published figures, listed below with their sources; the rest are example values. Enter your own numbers and press “Calculate” to run it with yours.

Per year

135.1 kWh

Of that, running

$23

Of that, standby

$0.63

Standby is 2.7% of the cost. Unplugging it saves $0.63 a year – and you have to plug it back in every day.

Power draw when running	90.00
Hours a day	4.00
Kilowatt-hours a year, running	131.50
Kilowatt-hours a year, standby	3.70
Kilowatt-hours a year	135.10
That is what it costs per year	$23

Assumptions behind this calculation

Days per year: 365
The remaining hours of the day count as standby. If you actually unplug it, enter 0 watts there.
The wattage comes from you. The rating plate states rated or maximum power, not automatically average power. For varying consumption, use measured kWh over a representative period. If that average already includes idle periods, use 24 hours and no additional standby.

How we calculate

Kilowatt-hours per year are watts when running times hours a day times 365.25 days, divided by 1,000. The remaining hours of the day run through the same formula at the standby draw.

Both amounts times your rate per kWh give the cost per year; the standby share is shown separately.

The reasoning behind these numbers, with sources, is in the article: Unplugging everything saves you $1.62 a year.

Frequently asked

How much does an appliance cost to run per year?

With the defaults – 90 watts, 4 hours a day, 0.5 watts on standby, 17.3 cents per kWh – it is 135.1 kWh and $23 a year.

How much does standby power cost per year?

In the example $0.63 a year, 2.7% of what this appliance costs to run. The default of 0.5 watts is the standby cap set by the European Commission for new devices sold in the EU; if you really unplug it, enter 0.

How do I convert watts to kWh and dollars?

Watts times hours a day times 365.25, divided by 1,000, is the kilowatt-hours per year; times the rate per kWh, the cost. In the example, 90 watts for 4 hours a day are 131.5 kWh when running.

What electricity rate does the calculator use?

17.3 cents per kWh by default. The source: EIA, Electric Power Monthly, table 5.3: 17.30 cents per kilowatthour, residential average for 2025.

Sources of the default values

Commission Regulation (EU) 2023/826, Annex III, European Commission, retrieved September 28, 2026.
Electric Power Monthly, Table 5.3, U.S. Energy Information Administration, retrieved August 24, 2026.