How to Calculate Kilowatt-Hours (kWh) for Any Household Appliance
Your electric company doesn't bill you for watts — it bills you for kilowatt-hours (kWh), a measure of energy used over time. Once you understand the relationship between power, time, and energy, you can predict the cost of running anything in your home.
The core formula
kWh = (Watts × Hours) ÷ 1000
Wattage tells you how much power a device draws. Multiply it by the number of hours you run it, then divide by 1,000 to convert watt-hours into kilowatt-hours.
Worked example
Imagine a 1500W air conditioner running 8 hours a day:
(1500 × 8) ÷ 1000 = 12 kWh / day
12 kWh × $0.16 = $1.92 / day
$1.92 × 30 = $57.60 / month
Why this matters
- Compare appliances fairly. A device's sticker wattage means little until you factor in how long it actually runs.
- Spot the big spenders. High-wattage devices used for many hours dominate your bill.
- Plan upgrades. Knowing the kWh cost helps you decide whether an efficient replacement pays for itself.
Finding an appliance's wattage
Check the label on the back or bottom of the device, the manufacturer's spec sheet, or a plug-in power meter. If only volts and amps are listed, multiply them: Watts = Volts × Amps.