How much does it cost to run an appliance?

This electricity cost calculator turns an appliance's wattage and running time into kilowatt-hours (kWh), then into money using the price per kWh you type in. What does a space heater cost to run every evening, and how fast does an LED bulb pay for itself? Everything is worked out in your browser, and "Copy link" gives you an address that reopens the calculation with your values.

How to use it

Fill in the "Price per kWh" and pick the currency: US dollar, pound or euro. The $0.17 shown at first is marked "example": replace it with the price per kWh on your bill.
On the "One appliance" tab, enter the "Power" in W or kW, the "Hours of use" and "Minutes", the period (per day or per week) and the "Days of use per year". Tick "Add standby power" to include the "Standby power (W)".
For a dishwasher or a car charge, choose "the energy per cycle (kWh)" and the "Number of cycles".
"Several appliances" totals a list and shows each one's share; "Compare two appliances" gives the saving per year and the payback time; "Conversions" turns W into kW, Wh into kWh and amps × volts into watts (120 V to start with).

Watts and kilowatt-hours, simply

Power, in watts (W), is what an appliance draws while running. Energy, in kilowatt-hours (kWh), is what it uses over time, and what the meter counts. The formula:

kWh = watts × hours ÷ 1,000

A worked example: a 1,500 W space heater running 4 hours a day uses 1,500 × 4 ÷ 1,000 = 6 kWh a day. At $0.17 per kWh, that is $1.02 a day. Over a 120-day winter: 720 kWh and $122.40. A thermostat switches it off at times: the rated wattage is a maximum.

Case	Sum	Result
3 W standby, TV watched 2 hours a day	3 × 22 × 365 ÷ 1,000	24.09 kWh a year
9 W LED instead of a 60 W bulb, 5 hours a day	51 × 5 × 365 ÷ 1,000	93.075 kWh saved a year
Dishwasher at 1.2 kWh per cycle, 5 cycles a week	1.2 × 5 × 52	312 kWh a year
Appliance drawing 15 A on 120 V	15 × 120	1,800 W

At $0.17 per kWh, the LED saves $15.82 a year, so a $4 bulb pays for itself in about three months.

Where to find an appliance's wattage

Check the rating plate (on the back or underneath) or the manual. Many large appliances carry an energy label with a yearly figure in kWh, which you can type straight into the comparison tab. For appliances whose draw varies, a plug-in power meter left for a few days shows the watts and adds up the kWh.

What uses the most power at home

In an electrically heated home, heating usually comes first, ahead of hot water, the fridge and freezer, and cooking. Ten devices on standby at a few watts each soon add up to tens of kWh a year.

A few sensible habits: turn the thermostat down a degree, switch devices off at the wall, wash at lower temperatures, defrost the freezer.

Your price per kWh

It depends on your plan, time-of-use periods and where you live, and it changes over time. The calculator gives no rate: check it on your bill. Fixed charges are not included.

Frequently asked questions

How do I calculate the running cost of an appliance?

Multiply the wattage by the hours of use and divide by 1,000 to get kWh, then multiply by your price per kWh. A 100 W TV on for 5 hours uses 0.5 kWh, which costs $0.085 at $0.17.

What does "Per month (average)" mean?

The yearly total divided by 12. For a heater, the winter months cost far more.

How is standby counted?

Over the hours when the appliance is not in use: 8,760 hours a year minus the hours of use.

Are the suggested appliance figures accurate?

No, they are rough orders of magnitude (a fridge: an average of 40 W over 24 hours). Replace them with your own appliances' figures.

Electricity cost calculator: power consumption in kWh

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