How to Calculate What an Appliance Costs to Run
Short answer: multiply the appliance's watts by the hours you use it, divide by 1,000 to get kilowatt-hours (kWh), then multiply by your price per kWh. cost = W × h ÷ 1,000 × price.
Step 1: find the power draw
Look for a rating plate or sticker on the back or bottom of the appliance, or check the manual. It will list watts (W). If it lists only amps (A) and volts (V), multiply them for an upper estimate of watts: a device rated 10 A at 120 V can draw up to about 1,200 W. That is a maximum; many devices draw less most of the time.
For appliances that cycle on and off, like refrigerators and dehumidifiers, a rated yearly kWh figure is better than watts × hours. You can find it on the yellow EnergyGuide label (for appliances that carry one) or in the ENERGY STAR product data.
Step 2: convert to kilowatt-hours
kWh = watts × hours ÷ 1,000
A 60 W fan running 10 hours uses 60 × 10 ÷ 1,000 = 0.6 kWh.
Step 3: find your price per kWh
The most accurate number is on your own bill: divide the total energy-related charges by the kWh used that month. Fixed monthly customer charges don't change with usage, so leave them out if you want the cost of extra usage. If you don't have a bill handy, the state average from the U.S. EIA is a reasonable stand-in; the U.S. average was 18.31¢/kWh in July 2026. See every state's average.
Step 4: multiply
cost = kWh × price per kWh
Worked examples at the U.S. average (18.31¢/kWh)
| Example | kWh | Cost |
|---|---|---|
| 1,500 W heater, 8 hours | 12 | |
| 60 W fan, 10 hours | 0.6 | |
| 1,000 W microwave, 15 minutes | 0.25 | |
| Dehumidifier rated 520 kWh/year | 520 |
Common mistakes
- Mixing up watts and kilowatts. 1,500 W is 1.5 kW. Forgetting to divide by 1,000 makes the answer 1,000 times too big.
- Assuming the label wattage is constant. Heaters with thermostats, fridges and dehumidifiers switch on and off, so they use less than the maximum × hours.
- Using the "delivery" or "supply" rate alone. Many bills split the price into supply and delivery; your real marginal rate is usually the sum of the per-kWh parts.
Skip the arithmetic with our electricity cost calculator.
Sources
- U.S. EIA, Electric Power Monthly, Table 5.6.A (July 2026).
- Virginia Cooperative Extension, Energy Series: Estimating Appliance and Home Electronic Energy Use.