Electricity Cost Calculator
Work out what an appliance adds to your power bill. Enter its wattage and how much you run it, or pick a common appliance from the list, and the calculator returns the energy used and the cost per day, month and year at your own price per kWh.
Wattages for the preset appliances are typical running figures, not nameplate ratings — check the label on your own unit. Refrigerators, air conditioners and other motor loads cycle on and off, so real use is lower than watts × hours suggests. The default price of 17 cents per kWh is near the US residential average in early 2026 (EIA); your own bill is the number that matters.
Formula and calculation
Worked example
A 1,500 W space heater used 3 hours a day, 7 days a week, at 17 cents per kWh: 1.5 kW × 3 h = 4.5 on a day it runs, 136.5 a month and 1,638 a year. The bill for that is $0.77 a day of use, $23.21 a month and $278.46 a year.
Watts, kilowatt-hours and what you actually pay
Watts measure how fast an appliance uses power; kilowatt-hours measure how much it used in total. A 1,500 W kettle and a 1,500 W heater draw the same power, but the kettle runs for three minutes and the heater for three hours, so their monthly costs differ by a factor of sixty.
Two things trip people up. Motor-driven appliances rarely draw their nameplate wattage continuously — a fridge cycles, a heat-pump dryer ramps up and down. And a bill's per-kWh price usually bundles supply and delivery, so the number on the summary line may differ from the one in the rate schedule. A plug-in power meter, free to borrow from many public libraries, settles the first question.
What the results mean
- Cost per month
- What the appliance costs you in a typical month at this usage and price. Months are the yearly figure divided by 12, so a 30 or 31 day month will not match to the cent.
- Energy per month
- The energy the appliance uses in a month, in kilowatt-hours — the unit your utility bills in. Compare it with the kWh line on your bill to see what share of the total this appliance is.
- Cost per year
- The cost over 52 weeks at this usage. This is the figure that makes an old fridge or a second freezer worth replacing.
- Energy per day of use
- Energy used on a day the appliance runs, from watts × hours. A 1,000 W appliance running one hour uses 1 kWh.
- Cost per day of use
- What one day of use costs at your price. Small numbers here add up: 77 cents a day is $280 a year.
- Energy per year
- Total energy for the year — the number to compare against the kWh per year that manufacturers publish on the energy label.
Frequently asked questions
How do I calculate the cost of running an appliance?
Multiply its power in kilowatts by the hours it runs, then by your price per kWh. A 1,500 W heater for 3 hours is 1.5 × 3 = 4.5 kWh, which at 17 cents is about 77 cents. Multiply by the days it runs to get a month or a year.
How many watts does a refrigerator use?
A frost-free fridge draws roughly 100 to 400 W while the compressor runs, then almost nothing while it cycles off, so the average is well below the nameplate. For an honest annual figure, use the kWh per year the manufacturer publishes on the energy label rather than watts × 24 hours.
Is a space heater cheaper than central heating?
Electric resistance heat costs the same per kWh whatever shape it takes, so a 1,500 W space heater and a 1,500 W electric furnace cost the same to run for an hour. A heat pump moves heat instead of making it, so it delivers several times more heat per kWh. Heating one occupied room with a space heater can still beat heating the whole house.
Why does this differ from my electricity bill?
Because few bills are a single flat rate: supply and delivery charges, seasonal tiers, time-of-use windows, fixed customer charges and taxes all sit on top of the per-kWh price. This calculator gives the energy part, which is usually the largest slice. Compare it with the kWh line on your bill rather than the total.
Do the preset wattages match my appliances?
They are typical running figures meant to get you close, not readings from your unit. The nameplate on the appliance, or a plug-in meter, has the real number — choose "Enter my own watts", type it in, and the rest of the calculation is unchanged.