kVA to HP Calculator

kVA to Horsepower (HP) Conversion Guide

Converting kVA (kilovolt-amperes) to HP (horsepower) is a critical calculation when matching electrical power supply to mechanical loads, such as motors, compressors, or industrial machinery. While kVA is used to describe electrical systems, HP measures the actual mechanical work a machine can perform. This guide explains the formula, key concepts, and how to apply the conversion accurately in real-world scenarios.

What’s the Difference Between kVA and HP?

• kVA measures **apparent electrical power**. It combines real power (kW) and reactive power (kVAR), and it reflects the total electrical demand from a system or motor.
• HP measures **mechanical output** — the power delivered by an electric motor to a load such as a pump, fan, or conveyor.

The two units belong to different systems: kVA is electrical, while HP is mechanical. To relate them, we must consider how efficiently electrical power is converted into mechanical power — that’s where power factor and motor efficiency come into play.

Conversion Formula

To convert kVA to HP, use this formula:

HP = (kVA × PF × 1000) ÷ (746 × Efficiency)

Where:

• kVA is apparent power
• PF is power factor (typically 0.8 – 0.95 for motors)
• Efficiency is motor efficiency (typically 0.85 – 0.95)
• 746 is the number of watts per horsepower (1 HP = 746W)

Alternate rearranged form:

HP = (kW × 1000) ÷ (746 × Efficiency)

Where kW = kVA × PF

Example Calculation

Let’s say you have a 50 kVA power source, with a power factor of 0.85 and motor efficiency of 0.9:

kW = 50 × 0.85 = 42.5 kW  
HP = (42.5 × 1000) ÷ (746 × 0.9)  
HP = 42500 ÷ 671.4 ≈ 63.28 HP

You can operate approximately a 63 HP motor with this system.

Understanding Power Factor

The power factor describes how efficiently electrical power is being converted into useful work. In an ideal case (PF = 1), all the power is used for mechanical output. In reality, motors introduce a lag (due to inductance), and the PF usually ranges from 0.8 to 0.95.

Understanding Efficiency

Efficiency refers to how much of the electrical input power actually gets converted into mechanical output. A high-efficiency motor wastes less energy as heat and friction. Efficiency is usually given in decimal form (e.g., 90% = 0.90).

Motor Efficiency by Type

Applications of kVA to HP Conversion

• Sizing generators for industrial motors
• Selecting transformers for HVAC compressors or chillers
• Planning electrical infrastructure for motor-heavy operations (e.g. irrigation pumps, conveyors)
• Upgrading or replacing legacy motors with higher-efficiency units

Common Mistakes to Avoid

• ⚠️ Assuming 100% efficiency — always include realistic efficiency (0.85–0.95)
• ⚠️ Ignoring power factor — especially critical for motors
• ⚠️ Mixing up real and apparent power — remember kW = kVA × PF
• ⚠️ Using incorrect PF or efficiency data — check nameplates or manufacturer specs

Best Practices

• Use conservative PF (0.85) and efficiency (0.9) when no exact data is available
• Round up horsepower results to avoid under-sizing
• Always verify power requirements with licensed engineers for critical applications

Frequently Asked Questions (FAQ)

What is the difference between HP and kW?

kW is a unit of electrical power, while HP is a unit of mechanical power. 1 HP = 0.746 kW (or 746 watts).

Why is efficiency included in the formula?

Not all input electrical power is converted into mechanical power. Efficiency accounts for losses due to heat, friction, and other factors inside the motor.

What happens if I ignore power factor?

You may dramatically overestimate the actual mechanical output. Power factor tells you how much of the electrical supply is actually doing useful work.

Can I convert kW to HP directly?

Yes. HP = (kW × 1000) ÷ (746 × efficiency)

Is this calculator valid for single-phase and three-phase motors?

Yes. The conversion from kVA to HP depends on total kVA, PF, and efficiency — it applies regardless of phase type.

Can I go from HP to kVA?

Yes, but you'll need to reverse the formula: kVA = (HP × 746 × efficiency) ÷ (1000 × PF)

Conclusion

Converting kVA to horsepower is essential for electrical and mechanical system integration. Whether you’re specifying a generator, choosing a transformer, or planning a motor control center, knowing how to relate electrical capacity to mechanical output ensures your equipment is sized accurately and performs efficiently.

Use the calculator above to make quick and accurate conversions, and always allow room for startup loads, aging inefficiencies, and future upgrades.