About the Motor Efficiency Calculator
What is the Motor Efficiency Calculator?
Motors use most of the electricity in Indian industry, so small motor efficiency gains matter. This calculator compares the shaft output (rated power × load) with the measured electrical input.
It shows the losses in kW and rupees per year, and what a premium-efficiency IE3 motor would save.
How to use the Motor Efficiency Calculator
- Rated Output (kW) (sample: 7.5)
- Load (% of rated output) (sample: 75)
- Measured Electrical Input (kW) (sample: 6.3)
- Running Hours per Year (sample: 4,000)
- Electricity Tariff (₹ per kWh) (sample: 8)
- Efficiency of a Premium (IE3) Motor (%) (sample: 90.4)
- Press Calculate Motor Efficiency (results also refresh as you type). The result card shows the Motor Efficiency, along with Shaft output, Losses, Yearly cost of losses and Yearly saving with an IE3 motor.
Formula used
Efficiency = Shaft output ÷ Electrical input × 100
- Shaft output = rated kW × load %
- IE3 input = shaft output ÷ IE3 efficiency
IS 12615 sets efficiency classes; IE2 is the minimum for most new motors sold in India, and IE3 is premium efficiency.
Worked example
These are the sample values already filled in the calculator above, and the result it returns for them:
| Input | Sample value |
|---|---|
| Rated Output (kW) | 7.5 |
| Load (% of rated output) | 75 |
| Measured Electrical Input (kW) | 6.3 |
| Running Hours per Year | 4,000 |
| Electricity Tariff (₹ per kWh) | 8 |
| Efficiency of a Premium (IE3) Motor (%) | 90.4 |
| Result | Value |
|---|---|
| Motor Efficiency | 89.29% |
| Shaft output | 5.63 kW |
| Losses | 0.68 kW |
| Yearly cost of losses | ₹21,600 |
| Yearly saving with an IE3 motor | ₹2,485 |
| Output in HP | 7.54 HP |
Tips for using the Motor Efficiency Calculator
- Motors are most efficient at 75–100% load; heavily oversized motors waste energy.
- Rewinding can lower efficiency by 1–2%; replace old, often-rewound motors.