Motor Power Formula
How to calculate motor power consumption, efficiency and running cost.
Motor Power Formulas
Electrical Input Power (kW) = Output kW ÷ (Efficiency / 100)
OR
Electrical Input (kW) = (HP × 0.746) ÷ (Efficiency / 100)
At rated load with efficiency = 90%:
10 kW motor input = 10 ÷ 0.90 = 11.11 kW drawn from grid
With load factor of 80%:
Actual Draw = 11.11 × 0.80 = 8.89 kW
HP to kW Conversion
1 HP = 0.746 kW
kW = HP × 0.746
HP = kW ÷ 0.746
Common Motor Sizes — HP to kW
| HP | kW | Typical IE2 Efficiency |
|---|---|---|
| 5 HP | 3.7 kW | 87.5% |
| 10 HP | 7.5 kW | 89.5% |
| 20 HP | 15 kW | 91.0% |
| 50 HP | 37 kW | 92.5% |
| 100 HP | 75 kW | 93.5% |