A kilowatt-hour (kWh) is the standard unit for measuring electricity consumption. It equals 1,000 watts used for 1 hour.
How to Calculate kWh
kWh = (Watts × Hours) ÷ 1,000
Example
A 100W light bulb running for 10 hours uses: (100 × 10) ÷ 1,000 = 1 kWh. At $0.16/kWh, that costs $0.16.
Average U.S. Household
The average American home uses about 900 kWh per month (~$150/month at the national average rate).
Peak vs. Off-Peak Rates
Many utilities charge different rates depending on time of day — peak hours (typically weekday afternoons/evenings) can cost 2–3× off-peak overnight rates under time-of-use plans. Running high-draw appliances (dishwashers, EV charging, laundry) during off-peak hours can meaningfully cut a monthly bill without reducing total usage.
Appliance kWh Reference
Rough monthly usage: refrigerator ~100 kWh, central AC (per cooling season month) ~200–400 kWh, electric water heater ~300 kWh, EV charging (full charge, ~60 kWh battery) ~15–20 kWh. Checking a device's wattage label against hours of daily use quickly reveals which appliances actually drive your bill.