Estimate an appliance's electricity usage and cost per day, week, month, and year.
Power (in watts or kilowatts) tells you the rate of energy use; multiplying by how many hours the appliance actually runs gives energy in kilowatt-hours (kWh) — the unit your electricity bill is priced in. The "capacity" field scales this down for appliances that don't run at full power the whole time, like a dimmed light or a partial-load motor.
Using an average year length (accounting for leap years) keeps the monthly and yearly figures consistent with each other, rather than the monthly total drifting depending on which specific month you'd pick.
Check the nameplate or spec sheet, usually printed as watts (W) or amps × volts. If it's rated in amps, multiply by your outlet's voltage (typically 120V in the US) to get watts.
It's on your utility bill, usually listed as a rate per kWh. National averages are a rough substitute if you don't have a bill handy.
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