Convert Horsepower to Kilovolt-Amps for motors and generators with precision
HP
PF
%
Result
10.383 kVA
Quick Conversions
How to Convert HP to kVA
Converting horsepower to kilovolt-amps requires accounting for power factor and motor efficiency. Horsepower measures real power output, while kVA represents apparent power in electrical systems.
kVA = (HP × 0.746) ÷ (Efficiency × Power Factor)
Where:
HP = Horsepower (mechanical power output)
0.746 = Conversion factor (1 HP = 0.746 kW)
Efficiency = Motor efficiency as a decimal (e.g., 90% = 0.90)
Power Factor = Ratio of real power to apparent power (typically 0.8 to 1.0)
Conversion Examples
Example 1: Standard Motor Conversion
Given: 25 HP motor, Power Factor = 0.8, Efficiency = 84%
Convert HP to kW: 25 × 0.746 = 18.65 kW
Calculate efficiency × PF: 0.84 × 0.8 = 0.672
Divide kW by product: 18.65 ÷ 0.672 = 27.75 kVA
Result: 25 HP = 27.75 kVA
Example 2: High-Efficiency Motor
Given: 50 HP motor, Power Factor = 0.95, Efficiency = 95%
Convert HP to kW: 50 × 0.746 = 37.3 kW
Calculate efficiency × PF: 0.95 × 0.95 = 0.9025
Divide kW by product: 37.3 ÷ 0.9025 = 41.33 kVA
Result: 50 HP = 41.33 kVA
Example 3: Generator Sizing
Given: 100 HP load, Power Factor = 0.85, Efficiency = 92%
Convert HP to kW: 100 × 0.746 = 74.6 kW
Calculate efficiency × PF: 0.92 × 0.85 = 0.782
Divide kW by product: 74.6 ÷ 0.782 = 95.40 kVA
Result: 100 HP = 95.40 kVA
HP to kVA Conversion Table
Standard conversion values at Power Factor = 0.8 and Efficiency = 100%
Horsepower (HP)
Kilovolt-Amps (kVA)
Kilowatts (kW)
1 HP
0.933 kVA
0.746 kW
2 HP
1.865 kVA
1.492 kW
3 HP
2.798 kVA
2.238 kW
5 HP
4.663 kVA
3.730 kW
7.5 HP
6.994 kVA
5.595 kW
10 HP
9.325 kVA
7.460 kW
15 HP
13.988 kVA
11.190 kW
20 HP
18.650 kVA
14.920 kW
25 HP
23.313 kVA
18.650 kW
30 HP
27.975 kVA
22.380 kW
40 HP
37.300 kVA
29.840 kW
50 HP
46.625 kVA
37.300 kW
60 HP
55.950 kVA
44.760 kW
75 HP
69.938 kVA
55.950 kW
100 HP
93.250 kVA
74.600 kW
125 HP
116.563 kVA
93.250 kW
150 HP
139.875 kVA
111.900 kW
200 HP
186.500 kVA
149.200 kW
250 HP
233.125 kVA
186.500 kW
300 HP
279.750 kVA
223.800 kW
Common Motor Applications
Industrial Motors
Large industrial motors (50-500 HP) typically operate at 0.85-0.95 power factor with 90-95% efficiency. These are used in manufacturing, pumps, and compressors.
Generator Sizing
When selecting generators, size for 125% of calculated kVA to account for startup surge. Most generators are rated in kVA rather than HP.
HVAC Systems
Air conditioning and ventilation motors (5-50 HP) commonly have power factors of 0.8-0.9 with efficiency ratings around 85-92%.
Agricultural Equipment
Farm equipment motors (10-100 HP) often run at 0.75-0.85 power factor. Proper sizing prevents voltage drops and equipment damage.
Power Factor and Efficiency Explained
What is Power Factor?
Power factor (PF) represents the ratio between real power (kW) and apparent power (kVA) in AC electrical systems. Values range from 0 to 1.0, with higher numbers indicating more efficient power usage. Most motors operate between 0.8 and 0.95 power factor.
What is Motor Efficiency?
Motor efficiency measures how effectively electrical input converts to mechanical output. Expressed as a percentage, typical motors range from 80% to 95% efficiency. Higher efficiency motors consume less electricity for the same horsepower output.
At 100% efficiency and 0.8 power factor, 1 HP equals 0.933 kVA. However, actual values vary based on motor efficiency and power factor. For a motor with 90% efficiency and 0.85 PF, 1 HP would be approximately 0.975 kVA.
What power factor should I use for motor conversions?
Standard induction motors typically operate at 0.8 to 0.9 power factor at full load. If the exact value is unknown, 0.8 is a conservative estimate for calculations. Check the motor nameplate for precise specifications.
Why is efficiency important in HP to kVA conversion?
Efficiency accounts for energy losses as heat during conversion. A motor with 85% efficiency requires more electrical input (kVA) than its mechanical output (HP) suggests. Ignoring efficiency results in undersized electrical infrastructure.
Can I convert HP directly to kVA without power factor?
No, power factor is required for accurate conversion because HP measures real power while kVA measures apparent power. Using power factor = 1.0 assumes perfect conditions and will underestimate actual kVA requirements.
How do I size a generator for an HP-rated motor?
Convert the motor HP to kVA using realistic efficiency and power factor values, then multiply by 1.25 to 1.5 for starting surge capacity. For a 50 HP motor at 0.8 PF and 90% efficiency, you would need approximately 65-78 kVA generator capacity.
What’s the difference between single-phase and three-phase conversions?
The HP to kVA formula remains the same for both single-phase and three-phase systems. The difference appears in current calculations and voltage considerations, but the power relationship between HP and kVA is identical.
Is mechanical HP the same as electrical HP?
Yes, mechanical horsepower and electrical horsepower both equal 746 watts. The distinction refers to measurement context: mechanical HP measures shaft output, while electrical HP refers to the equivalent electrical power consumption.
Why do generators use kVA instead of HP?
Generators are rated in kVA because they must supply apparent power to handle both resistive and reactive loads. kVA rating accounts for power factor variations in connected equipment, whereas HP only measures real power output.
