Motors, Generators & Electrification Equipment worked example

Motor Efficiency at 68% target nameplate efficiency: a worked example

This worked example runs the motor efficiency numbers for a tougher week than the baseline: 68% target nameplate efficiency instead of the typical 95%. Calculate motor efficiency from measured output and input power so energy and test engineers can verify nameplate efficiency and compare it to the target.

The inputs for this scenario

  • Motor shaft (output) power: 90 kW (held at the documented default)
  • Motor electrical (input) power: 95 kW (held at the documented default)
  • Target nameplate efficiency: 68 % (the input this scenario stresses; the baseline uses 95)

Working through the calculation

  • The calculation starts from the formula this tool documents: Motor efficiency = motor output power ÷ motor input power × 100.
  • Motor efficiency works out to 94.74 % at these inputs, and this is the headline figure for the scenario.
  • Efficiency gap to target works out to -26.74 points at these inputs.
  • Motor output power works out to 90 count at these inputs.
  • Motor input power works out to 95 count at these inputs.

How this compares with the baseline

  • Against the tool's baseline example, where target nameplate efficiency sits at 95% and the headline result is 94.74 %, this scenario lands almost exactly on the baseline at 94.74 %.
  • Use it during dynamometer or EOL testing to verify a unit against its nameplate IE class, or when comparing design iterations. A result at this level usually justifies acting on the stressed input before touching anything else, because every other figure in the table is downstream of it.

Results at a glance

  • Motor efficiency: 94.74 % (headline result)
  • Efficiency gap to target: -26.74 points
  • Motor output power: 90 count
  • Motor input power: 95 count

Run it with your numbers

  • To rerun this with your own numbers, open the live Motor Efficiency calculator, set target nameplate efficiency to your actual value, and adjust the remaining inputs to match your operation.

Last reviewed 2026-05-12.