Use the strongest source available
- A compatible plug-in or circuit energy meter.
- Manufacturer technical documentation for the exact model.
- The rating label on the appliance.
- A category benchmark used as an explicit estimate.
Convert amps only when necessary
If a label gives voltage and current but not watts, apparent power can be approximated by multiplying volts and amps. For some motors and electronics, actual power may be lower because power factor matters.
Core formulaApproximate watts = volts × amps
Maximum is not average
A label often communicates safe electrical requirements or maximum input. Computers, variable-speed motors, ACs, refrigerators, and pumps may draw less during ordinary operation. Record the source as estimated unless you measured it.
Run your own scenario