Motor Efficiency Calculator
Calculate motor efficiency and the annual cost of its losses.
About Motor Efficiency Calculator
Motor efficiency looks high in percentage terms but the losses are continuous. Over 6,000 hours a year even a 1.5 kW loss costs more than the motor, which is why efficiency classes are regulated. The lifetime energy cost of an industrial motor is typically 50 to 100 times its purchase price, so two points of efficiency dominate the buying decision.
Formula
Motor Efficiency
η = output ÷ input × 100
- losses
- Copper, iron, friction and windage losses combined
Worked example
With the default values below, Motor Efficiency Calculator returns Efficiency of 90.909%. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Shaft output powerminimum 0 kW
- 15 kW
- Electrical input powerminimum 0.001 kW
- 16.5 kW
- Operating hours per yearaccepts 0–8,760 h
- 6,000 h
- Energy price per kWhminimum 0
- 0.15
Results
- Efficiency
- 90.909%
- Losses
- 1.5000 kW
- Annual Energy Lost
- 9,000.0 kWh
- Annual Cost of the Losses
- $1,350.00
- Annual Saving From Two Points More Efficiency
- $319.67
Step by step
- 1Values used
- 2Motor Efficiency
- 3Efficiency= 90.909
- 4Losses= 1.5000 kW
- 5Annual Energy Lost= 9,000.0 kWh
- 6Annual Cost of the Losses= 1,350.00
- 7Annual Saving From Two Points More Efficiency= 319.67
Assumptions and limits
- The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax or fees or charges into account.
- Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
Frequently Asked Questions
How is Motor Efficiency calculated?
η = output ÷ input × 100 Motor efficiency looks high in percentage terms but the losses are continuous. Over 6,000 hours a year even a 1.5 kW loss costs more than the motor, which is why efficiency classes are regulated.
Why does Motor Efficiency matter?
The lifetime energy cost of an industrial motor is typically 50 to 100 times its purchase price, so two points of efficiency dominate the buying decision.
What values do I need to enter?
This calculator takes 4 inputs: Shaft output power, Electrical input power, Operating hours per year, Energy price per kWh. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.