Wattage vs. Kilowatt-Hours: What Actually Determines Cost
Wattage measures an appliance's power draw rate — how much electricity it uses at any given moment while running — while a kilowatt-hour measures actual energy consumed over time (wattage combined with hours of use), and it's specifically kilowatt-hours, not wattage alone, that an electricity bill charges for and that determines actual cost.
This distinction is the reason wattage alone can't answer "how much does this cost to run" without also knowing how long it runs.
What wattage actually measures
Wattage is a rate — like miles per hour for a car — describing how much power an appliance draws while actively running, at any given instant. A higher-wattage appliance draws power faster than a lower-wattage one, but this alone says nothing about total energy consumed unless combined with how long it actually runs.
What a kilowatt-hour actually measures
A kilowatt-hour is a unit of actual energy consumed — equivalent to running a 1,000-watt (1 kilowatt) appliance for one hour — combining both power rate (wattage) and duration (hours) into a single figure. This is the actual quantity an electricity bill charges for, since it represents real energy used, not just a momentary rate.
Why this matters for comparing appliances
A very high-wattage appliance used briefly (a hair dryer for a few minutes) can consume far fewer total kilowatt-hours — and therefore cost far less — than a much lower-wattage appliance left running for many hours (a computer or a light left on all day), which is exactly why wattage alone is a misleading way to compare appliances' actual cost impact.