Loading Calculator...
Please wait a moment
Please wait a moment
Typical motor efficiency: 80-95%
Typical motor PF: 0.80-0.90
HP = (kVA × PF × η) ÷ 0.746
Where:
Maximum motor HP that can be powered from kVA at different power factors:
| kVA | HP (PF=0.90) | HP (PF=0.85) | HP (PF=0.80) |
|---|---|---|---|
| 1 | 1.03 | 0.97 | 0.91 |
| 2 | 2.05 | 1.94 | 1.82 |
| 3 | 3.08 | 2.91 | 2.74 |
| 5 | 5.13 | 4.85 | 4.56 |
| 7.5 | 7.70 | 7.27 | 6.84 |
| 10 | 10.27 | 9.70 | 9.12 |
| 15 | 15.40 | 14.55 | 13.68 |
| 20 | 20.54 | 19.39 | 18.24 |
| 25 | 25.67 | 24.24 | 22.80 |
| 30 | 30.80 | 29.09 | 27.36 |
| 40 | 41.07 | 38.79 | 36.48 |
| 50 | 51.34 | 48.49 | 45.60 |
| 75 | 77.01 | 72.73 | 68.40 |
| 100 | 102.68 | 96.98 | 91.20 |
| 150 | 154.02 | 145.47 | 136.80 |
| 200 | 205.36 | 193.96 | 182.40 |
kVA to HP conversion tells you how much mechanical horsepower a given electrical supply can deliver through a motor. Kilovolt-amperes (kVA) measure the total apparent power flowing through electrical equipment such as transformers and generators. Horsepower (HP) measures the mechanical work output at a motor's shaft. The conversion is not a simple fixed ratio because it depends on two critical motor characteristics: efficiency, which accounts for heat and friction losses inside the motor, and power factor, which reflects the proportion of current actually doing useful work versus maintaining the magnetic field. Knowing this conversion helps you determine the largest motor or combination of motors that your existing electrical infrastructure can safely support.
Find the kVA rating on your transformer, generator, or UPS nameplate. This is the maximum apparent power the equipment can deliver continuously without overheating.
Convert apparent power to real power: kW = kVA × PF. Typical motor power factors range from 0.80 to 0.90. This step filters out the reactive component that does not produce mechanical work.
Not all electrical input becomes shaft output. Multiply by the motor efficiency (typically 0.85-0.96) to find the actual mechanical power available: Output kW = kW × η.
Divide by 0.746 to convert kilowatts to horsepower: HP = Output kW ÷ 0.746. For a 50 kVA source at 0.85 PF and 0.90 efficiency: HP = (50 × 0.85 × 0.90) ÷ 0.746 = 51.3 HP.
When upgrading or replacing motors, you need to verify that the existing transformer or generator has enough kVA capacity for the new motor's HP requirement. This prevents overloading and equipment failures.
Industrial facilities need to know how much mechanical HP their electrical system can support before adding new production equipment. This conversion guides expansion decisions and prevents costly infrastructure surprises.
When a transformer trips or a generator overloads, engineers verify that the total HP of connected motors does not exceed the available kVA. This conversion is essential for diagnosing overload conditions.
| Generator kVA | Max Running HP | Max DOL Start HP | Max VFD Start HP |
|---|---|---|---|
| 25 | 24 | 5-7 | 20-24 |
| 50 | 48 | 10-15 | 40-48 |
| 100 | 97 | 20-30 | 80-97 |
| 150 | 145 | 30-45 | 120-145 |
| 200 | 194 | 40-60 | 160-194 |
| 300 | 290 | 60-90 | 240-290 |
| 500 | 484 | 100-150 | 400-484 |
| 750 | 726 | 150-225 | 600-726 |
| 1000 | 968 | 200-300 | 800-968 |
Assumes PF=0.85, η=0.90. DOL start limited by 6x inrush current. Actual values depend on specific motor and generator characteristics.
Multiply the generator kVA rating by the power factor and efficiency, then divide by 0.746. For a 200 kVA generator at 0.85 PF and 0.90 efficiency: (200 × 0.85 × 0.90) ÷ 0.746 = 205.4 HP maximum. However, you should also account for other loads on the generator and reserve capacity for motor starting surges.
The conversion depends on power factor and motor efficiency, which vary by motor size, type, manufacturer, and loading condition. A small 1 HP motor might have 75% efficiency, while a large 200 HP motor achieves 96%. Similarly, power factor improves with motor loading and size. These variations make a universal fixed ratio impossible.
Nameplate HP is the maximum continuous output the motor is designed to deliver at rated conditions. Actual output depends on the mechanical load connected to the shaft. A lightly loaded motor delivers less HP but still draws significant kVA due to magnetizing current, which lowers the effective power factor and makes the kVA-to-HP ratio worse.
At altitudes above 1000 meters (3300 feet), motors must be derated because thinner air provides less cooling. A motor may need to be derated by approximately 1% for every 100 meters above 1000m, effectively reducing the HP output available from a given kVA supply. This is critical for installations in mountainous regions or high-altitude cities.
UPS systems can support motor loads but require careful sizing. Motors have high inrush currents during starting (5-8x running current), and many UPS units cannot handle this surge. You need a UPS rated for at least 3x the motor's running kVA to accommodate starting, or use a soft starter or VFD to limit inrush current to manageable levels.