HP to kW Calculator
Calculate the electrical input power (kW) required for an electric motor based on its Horsepower rating. Critical for generator sizing.
Motor Specifications
Electrical Input Required
Power Flow
Why Output HP ≠ Input kW?
A common mistake is assuming 1 HP = 0.746 kW for generator sizing. That formula only tells you the mechanical output power at the motor shaft.
Real-world motors are not 100% efficient. They generate heat and have friction. To produce 10 HP of work, a motor might consume 11 HP worth of electricity. This "Input Power" is what your generator must supply.
The Formula Used:
Input kW = (HP × 0.746) / Efficiency
Example: A 10 HP motor at 90% efficiency requires 8.29 kW of input power, not 7.46 kW.
Standard NEMA Motor Ratings (Approx)
| Horsepower | Input kW (Typical) | 208V 3Ø Amps | 480V 3Ø Amps |
|---|---|---|---|
| 1 HP | 1.0 kW | 3.5 A | 1.5 A |
| 5 HP | 4.5 kW | 16 A | 7 A |
| 10 HP | 8.8 kW | 31 A | 14 A |
| 20 HP | 17.2 kW | 59 A | 27 A |
| 50 HP | 42.5 kW | 143 A | 65 A |