Horsepower (HP) and kilowatts (kW) are both units of power. In industrial settings, motors and engines are often rated in HP on the nameplate, while electricity calculations require kW. Converting between the two is a daily need for plant engineers, electricians, and maintenance teams.
Examples:
Examples:
| Horsepower (HP) | Kilowatts (kW) | Common Application |
|---|---|---|
| 0.5 HP | 0.37 kW | Small pumps, fans, conveyors |
| 1 HP | 0.75 kW | Small machinery, pumps |
| 2 HP | 1.49 kW | Light duty machinery |
| 3 HP | 2.24 kW | Grinders, small compressors |
| 5 HP | 3.73 kW | Pumps, machine tools |
| 7.5 HP | 5.59 kW | Compressors, fans |
| 10 HP | 7.46 kW | Industrial pumps, conveyor drives |
| 15 HP | 11.2 kW | Air compressors, mixers |
| 20 HP | 14.9 kW | Medium machinery, compressors |
| 25 HP | 18.6 kW | Large pumps, conveyors |
| 30 HP | 22.4 kW | Industrial HVAC fans |
| 40 HP | 29.8 kW | Heavy machinery drives |
| 50 HP | 37.3 kW | Large compressors, heavy conveyors |
| 75 HP | 55.9 kW | Large industrial motors |
| 100 HP | 74.6 kW | Heavy industrial drives |
| 150 HP | 111.9 kW | Large process equipment |
| 200 HP | 149.1 kW | Very heavy industrial drives |
Horsepower was originally defined by James Watt in the 18th century to compare steam engine power to horse power. It became the dominant unit in English-speaking countries for engines and motors.
The kilowatt (kW) is the SI (metric) unit of power, used in electrical systems worldwide. In India and most of the world, electricity bills, industrial standards, and electrical engineering use kW and kWh.
The reason you need to convert is that motor nameplates often still show ratings in HP (especially older motors and imported equipment), while electricity cost calculations, tariff structures, and energy audits all work in kW.
The HP rating on a motor nameplate is the mechanical output power — what the motor delivers to the shaft. The actual electrical power drawn from the grid is higher because no motor is 100% efficient.
Example: A 10 HP (7.46 kW) motor with 92% efficiency:
Actual electrical draw = 7.46 / 0.92 = 8.11 kW
Typical motor efficiency values:
| Motor Size | IE1 (Standard) | IE2 (High Eff.) | IE3 (Premium) |
|---|---|---|---|
| 5 HP (3.7 kW) | 85% | 87% | 89% |
| 10 HP (7.5 kW) | 88% | 90% | 91.5% |
| 25 HP (18.5 kW) | 90.5% | 92% | 93.5% |
| 50 HP (37 kW) | 92% | 93% | 94.5% |
| 100 HP (75 kW) | 93.5% | 94.5% | 95.5% |
There are actually several different definitions of "horsepower." For industrial motors, use mechanical horsepower:
| Type | kW Equivalent | Used For |
|---|---|---|
| Mechanical HP (hp) | 0.74570 kW | Electric motors, engines — most common in industry |
| Metric HP (PS) | 0.73550 kW | European automotive (slightly different) |
| Boiler HP | 9.8095 kW | Steam boilers only — much larger unit |
| Electrical HP | 0.74600 kW | Electrical machinery (virtually same as mechanical) |
For virtually all practical industrial purposes, use 1 HP = 0.746 kW.
Once you know the kW equivalent of your motor, you can calculate its electricity cost using:
Example: A 25 HP pump, running 200 hours/month, at ₹7/kWh, 90% efficient:
Monthly Cost = 25 × 0.746 × 200 × 7 ÷ 0.90 = ₹29,039/month
Is 1 HP equal to 1 kW?
No. 1 HP is approximately 0.746 kW, which is about 74.6% of 1 kW. They are related but not equal. 1 kW is slightly more powerful than 1 HP.
How do I convert HP to kVA?
First convert HP to kW (multiply by 0.746), then divide by the power factor to get kVA. For example, a 10 HP motor (7.46 kW) with a power factor of 0.85: kVA = 7.46 / 0.85 = 8.78 kVA.
What is the HP rating on a motor nameplate — input or output?
The HP rating on a motor nameplate is the output (shaft) power. The actual electrical input power drawn from the supply will be higher than this, divided by the motor's efficiency. Always account for motor efficiency when calculating electricity consumption.
How do I find the HP of a motor if the nameplate is missing?
If the nameplate is missing, you can measure the actual current draw with a clamp meter, then calculate: kW = √3 × V × I × PF × Efficiency (for 3-phase motors). This gives you input kW, from which you can estimate output HP. Alternatively, check the motor frame size — standard motor frames have associated typical HP ratings.
Why do Indian motor catalogues show both HP and kW?
India uses both conventions because older industrial standards (especially British-influenced ones) used HP, while modern IS standards and electrical regulations use kW. Most Indian motor manufacturers list both on the nameplate and in their catalogues to serve both conventions.
Calculate the electricity cost of your motors:
Open Electricity Cost Calculator →Related: Power Factor Calculator | Monthly Energy Calculator | OEE Calculator