What is the difference between kW and kVA?

kW (kilowatts) is real power — the actual work done. kVA (kilovolt-amperes) is apparent power, which includes the reactive component due to inductive loads. kVA = kW / power factor.

What power factor should I use?

Most AC induction motors operate between 0.80 and 0.95 power factor at full load. If unknown, use 0.85 as a conservative estimate. Check the motor nameplate for the rated PF.

Why does efficiency matter?

Motor efficiency accounts for internal losses (heat, friction). A 90% efficient motor drawing 10 HP of shaft output actually consumes more electrical input. The formula divides by efficiency to get true electrical input.

What is 1 mechanical horsepower in watts?

1 mechanical horsepower equals exactly 745.7 watts. For calculations this is rounded to 746 W. Electrical horsepower (used in the US for motors) is also defined as 746 W.

How do I size a generator for a motor?

Calculate running kVA using this tool and add 20–25% margin for continuous operation. Direct-on-line motors draw 5–7× rated current at startup, typically requiring a generator with 2–3× running kVA to handle starting surge unless a soft starter or VFD is used.

Horsepower to kVA Calculator

Convert horsepower (HP) to kilovolt-amperes (kVA) instantly by entering horsepower, efficiency, and power factor.

Input Values

Horsepower (HP)

Motor Efficiency (%) — check nameplate, or use 90% if unknown

Power Factor (PF) — 0.01 to 1.00

Apparent Power

—

kilovolt-amperes (kVA)

Calculation Breakdown

Horsepower	—
Watts per HP	746 W
Total input power (kW)	—
Motor efficiency	—
Power factor	—
Result (kVA)	—

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

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Summary

Convert horsepower (HP) to kilovolt-amperes (kVA) instantly by entering horsepower, efficiency, and power factor.

How it works

Enter the horsepower (HP) rating of the motor or equipment (1 HP = 746 W).
Enter the motor efficiency percentage (check nameplate, or use 90% if unknown).
Enter the operating power factor (PF), typically 0.80 to 0.95 for AC induction motors.
The calculator applies the formula: kVA = (HP × 0.746) / (Efficiency × PF) and displays apparent power.

Use cases

Size a generator or transformer for an electric motor.
Determine apparent power for electrical panel design.
Convert motor nameplate HP to kVA for utility billing estimates.
Calculate generator capacity needed to start a motor.
Verify electrical supply ratings match motor requirements.
Convert pump or compressor HP ratings to electrical load.

Frequently Asked Questions

Last updated: 2026-09-19 · Reviewed by Nham Vu