Kilowatt-hour definition
A kilowatt-hour is the energy used when one kilowatt of power runs for one hour. One kilowatt equals 1,000 watts, so a 1,000-watt device running at full power for one hour uses 1 kWh.
The word hour is part of the energy measurement. A kWh is not the number of kilowatts used in an hour; it is power multiplied by time.
kW versus kWh
A kilowatt (kW) describes the rate at which a device is drawing or delivering power at a moment. A kilowatt-hour (kWh) describes how much energy accumulated across a period of time.
A useful comparison is speed versus distance: kW is like the speed, while kWh is like the distance accumulated as that speed continues.
A simple example
A 1,000-watt appliance equals 1 kilowatt. Running it at full power for one hour uses 1 kWh. At the 2026-05 U.S. residential average of 18.44 cents per kWh, that hour costs about 18.44 cents in energy charges.
Convert watts to kilowatt-hours
Divide watts by 1,000 to convert power to kilowatts, then multiply by the number of operating hours. For equipment used on several days, multiply again by the number of days.
Convert kWh to electricity cost
Multiply energy use by the electricity price in dollars per kWh. If a bill lists cents per kWh, divide that number by 100 before multiplying.
Use a state average for a comparison and the all-in price from your own bill for a household-specific historical estimate.
Why nameplate watts can mislead
Many products cycle or vary power. Refrigerators, heat pumps, computers, and variable-speed motors rarely remain at one fixed wattage. Measured kWh automatically captures those changes.
Reading kWh on an electric bill
The bill may show beginning and ending meter readings, total kWh for the billing period, average kWh per day, and comparisons with earlier months. Compare billing-period length before judging whether usage rose.
Dollar totals can change because of usage, price, fixed charges, taxes, credits, or corrections. Compare kWh per day first when diagnosing a change in consumption.
Everyday kilowatt-hour examples
These examples separate power from energy. The device wattage tells you the rate of use; the time converts that power into kWh.
Costs use the 2026-05 U.S. residential average of 18.44¢/kWh. Your utility price may be higher or lower.
Calculate kWh and cost with your own numbers
Your inputs
Calculate operating cost
Live estimate
(1000 W ÷ 1,000) × 1 hr × 30 days × $0.184/kWhActual use can differ when equipment cycles or changes power. Measure at the wall when precision matters.
Continue from the definition to a real bill
Sources and further reading
EIA: Electricity explainedDOE Energy SaverCalculations are estimates. Utility bills, appliance measurements, and manufacturer documentation take priority over generic examples.