To estimate the wattage of an appliance, check for the wattage listed on the appliance's Underwriter Laboratory label. If the wattage is not listed, look for the voltage and amperes details on the label, and use them to calculate the appliance's wattage. Alternatively, use an electricity usage monitor to determine the wattage of the appliance.
The Underwriter Laboratory label on an appliance normally provides the appliance's name, manufacturer and model number details along with its wattage, voltage and amperage.
If only the voltage and amperage details are given on the label, multiply the two figures to arrive at the appliance's wattage in watts. Divide this result by 1,000 to calculate the wattage in kilowatts.
To determine the wattage of an appliance accurately, connect an electricity usage monitor to the appliance, and then connect the former to a power outlet. Read the power being used by the appliance off the monitor's screen. Normally, the unit measures the wattage an appliance uses in an hour.
The monitor provides the active power usage in watts. It can also be used to calculate an appliance's apparent power usage using the voltage and amperage information displayed on the screen. Press the appropriate buttons on the monitor to know the appliance's voltage and amperage, and use these details to calculate its apparent power usage as before.