Electricity cost = watts × hours ÷ 1,000 × your rate per kWh. A 1,500 W space heater running 8 hours a day uses 12 kWh and costs $2.20 a day at the 18.31 cent U.S. residential average, which is $66.83 a month and $801.98 a year. This electricity cost calculator, which doubles as a kWh cost calculator, does the sum for up to eight appliances at once.
How the electricity cost is calculated
Power in watts tells you how fast an appliance uses energy; a kilowatt-hour (kWh) is 1,000 watts running for one hour. The Department of Energy method, as published by Virginia Cooperative Extension, is: wattage × hours used per day ÷ 1,000 = daily kWh, then multiply by the days of use and by your utility rate.
Cost per day = watts × quantity × hours ÷ 1,000 × rate per kWh
A month is 365 ÷ 12 = 30.4 days. Your rate is the price per kWh on the bill; the calculator starts from the state average and you can overwrite it.
Worked example: a 1,500 W space heater
- Energy: 1,500 W × 8 h ÷ 1,000 = 12 kWh a day
- Cost per day: 12 kWh × $0.1831 = $2.20
- Per month: 12 × 365 ÷ 12 = 365 kWh, $66.83
- Per year: 4,380 kWh, $801.98
State average electricity rates
The rates come from the U.S. Energy Information Administration, Electric Power Monthly Table 5.6.A, residential sector, July 2026. The U.S. average is 18.31 cents per kWh. The same 365 kWh a month costs $46.43 in Louisiana (12.72 cents), $57.96 in Texas (15.88), $66.83 at the U.S. average, $122.68 in California (33.61) and $175.20 in Hawaii (48.00 cents). Rates move through the year, so replace the preset with the number on your latest bill when you have it.
Cost of common appliances
Wattages are the Department of Energy figures (the midpoint where a range is given); the hours are typical use that you can change.
| Appliance | Watts | Hours a day | kWh a month | Cost a month at 18.31 cents |
|---|---|---|---|---|
| Laptop | 50 W | 6 | 9.1 | $1.67 |
| Flat screen TV | 120 W | 5 | 18.3 | $3.34 |
| Ceiling fan | 120 W | 8 | 29.2 | $5.35 |
| Dishwasher | 1,800 W | 1 | 54.8 | $10.02 |
| Clothes dryer | 3,400 W | 1 | 103.4 | $18.94 |
| Refrigerator | 725 W | 8 | 176.4 | $32.30 |
| Dehumidifier | 785 W | 12 | 286.5 | $52.46 |
| Water heater, 40 gal | 5,000 W | 3 | 456.3 | $83.54 |
The refrigerator rating is the power while the compressor runs, so 8 hours stands for its share of the day; a meter shows your real figure.
Add up the whole load
Press "Add another appliance" to build a list. The table under the result gives each one's kWh and dollars a month, and the top line is the total. To see how much of a room's lighting you could save, run the same bulbs through the LED savings calculator.
What to do next
- Work out energy from watts and hours alone with the kWh calculator.
- Convert a nameplate to current with the amp calculator.
- Compare heating options with the space heater calculator.
- Planning a garage charger? See the EV charger installation cost calculator.
- Size the bulbs for a room with the lumens calculator.
- Browse the electrical calculators.