Electricity Cost Calculator
What an appliance costs to run, per day, month and year.
The appliance
Pick one, or type your own
Starts at the US household average
This works out what any appliance costs to run. Enter its power draw in watts, how long it runs, and your electricity rate.
It returns the cost per day, month and year, so you can see whether something is worth unplugging or replacing.
How electricity is billed
Electricity is billed by the kilowatt-hour: one kilowatt of power drawn for one hour. Your bill is simply the kilowatt-hours you used multiplied by your rate.
So two things decide the cost, and only two: how much power a device draws, and how long it runs. A 1,500 W heater and a 15 W lamp differ by a factor of a hundred, but the lamp left on all day can still cost more than the heater used briefly.
That is the part people get wrong. The biggest bills usually come from things that run for hours — heating, cooling, water heating — rather than from the devices that feel powerful.
Dividing by 1,000 is the step to remember: appliances are labelled in watts, but electricity is billed in kilowatt-hours.
What to enter
- Power draw
- In watts, from the label, the manual or a plug-in meter. Some appliances list amps instead: multiply amps by volts (120 in the US) to get watts.
- Hours a day / days a week
- How long it actually runs, not how long it is plugged in. A fridge cycles on and off, so its real running time is well under 24 hours.
- Your rate per kWh
- From your bill. The US average is around 17 cents but varies widely by state, and many plans charge more at peak times.
Roughly what common appliances draw
- Space heater
- 1,500 W. One of the most expensive things in a home to run, because it draws heavily for long stretches.
- Clothes dryer
- 3,000 to 5,000 W, but only for the length of a cycle.
- Air conditioner (window)
- 500 to 1,500 W, cycling on and off.
- Refrigerator
- 100 to 400 W while the compressor runs, which is a fraction of the day. Cheap per hour, but it never switches off.
- Gaming PC
- 300 to 600 W under load, far less when idle.
- LED bulb
- 8 to 15 W. Even left on constantly, it costs very little.
What this assumes
The device draws its rated power the whole time it is on. Anything with a thermostat or compressor cycles, so real use is lower.
One flat rate is used. Time-of-use tariffs charge more at peak hours, and tiered plans raise the rate above a monthly threshold.
How to calculate what an appliance costs to run
Watts to kilowatts, multiply by hours, multiply by your rate.
- ÷ 1000
- Converts watts into kilowatts
- hours
- How long it actually runs
- rate
- What your utility charges per kWh
Find the wattage. Check the label or manual. If it lists amps, multiply amps by volts.
Convert to kilowatts. Divide by 1,000. A 1,500 W heater is 1.5 kW.
Multiply by running hours. That gives kilowatt-hours, the unit you are billed in.
Multiply by your rate. Take the rate from your bill rather than a national average, since it varies a great deal by state.
See a worked example: a 1,500 W space heater running 4 hours a day
- Power
- 1,500 W
- Use
- 4 hours a day
- Rate
- $0.17 per kWh
Convert: 1,500 ÷ 1,000 = 1.5 kW.
Daily use: 1.5 × 4 = 6 kWh.
Daily cost: 6 × $0.17 = $1.02.
Over a 30-day month that is about $30.60, and over a four-month winter roughly $122.
About $1.02 a day, or $30.60 a month
Frequently asked questions
A 1,500 W heater costs about $0.26 an hour at 17 cents per kWh, so roughly $1.02 for four hours a day and about $30 a month.
Nearly all plug-in electric heaters are 1,500 W at their top setting, so the brand makes almost no difference. What matters is how long it runs and whether you are heating one room or trying to heat a house.
It is on your bill, usually shown as a price per kWh. Divide the total charge by the kilowatt-hours used if it is not listed directly.
Watch for extra lines: many bills add delivery, supply and fixed charges on top of the energy rate, so your true cost per kWh is often higher than the headline figure.
Almost always heating and cooling, then water heating. Together they typically dominate a bill.
Individual gadgets rarely matter much by comparison. Replacing a few bulbs is worth doing, but it will not offset an inefficient heating setup.
A little, but less than people think. Modern devices draw roughly 0.5 to 3 W on standby, which is a few dollars a year each.
It adds up across a whole house, perhaps $50 to $100 a year, but the effort of unplugging everything is better spent on the heating, cooling and water-heating side.
Multiply amps by volts. In the US that is normally 120 V, so a 12.5 amp appliance draws about 1,500 W.
Large appliances like dryers and ovens often run on 240 V circuits, so use 240 for those or the answer will be half what it should be.
Problems people actually run into
Judging cost by how powerful something feels
A dryer draws far more watts than a fridge, yet the fridge often costs more over a year because it never stops while the dryer runs for an hour at a time.
Always multiply by hours before comparing. Power alone tells you almost nothing about what a device costs you.
Using the rated wattage for something that cycles
Fridges, freezers, air conditioners and thermostatic heaters do not draw full power continuously. They run until they hit temperature, then stop.
Using the rated figure and 24 hours a day badly overstates the cost. A plug-in energy meter left on for a week gives the honest number.
Results are estimates for general information only and are not professional financial, medical, or legal advice. Read our full disclaimer.
Last updated: September 3, 2026