Energy worked example

Motor Energy Cost at 99% motor efficiency: a worked example

This scenario runs the motor energy cost calculation on the strong side: 99% motor efficiency, with every other input held at its documented default. Use when estimating energy cost for pumps, fans, conveyors, compressors, and driven equipment.

The inputs for this scenario

  • Motor horsepower: 25 hp (unchanged)
  • Motor efficiency: 99 % (raised for this scenario; the documented default is 92)
  • Average load: 70 % (unchanged)
  • Runtime: 3,200 hr / yr (unchanged)
  • Electricity rate: 0.12 $ / kWh (unchanged)

Working through the calculation

  • Applying the documented formula (Input kW = horsepower × 0.746 × load ÷ efficiency) to the inputs above produces each figure below.
  • At this operating point the engine returns 5,064 $ / yr for annual motor cost, the number this scenario is built around.
  • At this operating point the engine returns 13.19 kW for motor input power.
  • At this operating point the engine returns 42,198 kWh for annual energy.
  • At this operating point the engine returns 1.58 $ / hr for hourly cost.

How this compares with the baseline

  • Against the tool's baseline example, where motor efficiency sits at 92% and the headline result is 5,449 $ / yr, this scenario comes in 7.07% below the baseline at 5,064 $ / yr.
  • Use it when building an energy audit, justifying a premium-efficiency or VFD upgrade, or comparing two motors for the same duty. Treat this as a target state: the delta against the baseline quantifies what the improvement is worth before you commit to chasing it.

Results at a glance

  • Annual motor cost: 5,064 $ / yr (headline result)
  • Motor input power: 13.19 kW
  • Annual energy: 42,198 kWh
  • Hourly cost: 1.58 $ / hr

Run it with your numbers

  • Every input above is editable in the live Motor Energy Cost calculator, which recalculates instantly and can be shared with the inputs intact.

Last reviewed 2026-05-12.