What is the difference between kW and kVA?

kW (kilowatts) is real power — the portion of electrical power that performs actual useful work such as running motors or heating elements. kVA (kilovolt-amperes) is apparent power — the total power drawn from the supply, including both real and reactive components. They are related by the power factor: kW = kVA × PF.

What is power factor?

Power factor (PF) is a dimensionless ratio between 0 and 1 that describes how efficiently an AC circuit converts apparent power into real power. A PF of 1.0 means all supplied power does useful work (purely resistive load). Lower values indicate reactive loads (motors, transformers) where some power is stored and returned rather than consumed.

Why do I need to know kVA if I only care about kW?

Generators, UPS systems, and transformers are rated in kVA because they must supply the full apparent power regardless of the load's power factor. If you size equipment based on kW alone and ignore power factor, you risk overloading the supply — the equipment may not be able to deliver the required current even if real power demand appears within limits.

What is a typical power factor for common loads?

Resistive loads (heaters, incandescent lights): PF ≈ 1.0. Induction motors at full load: PF ≈ 0.85–0.95. Induction motors at partial load: PF ≈ 0.70–0.85. Fluorescent lighting with ballasts: PF ≈ 0.90–0.95. Variable-frequency drives: PF ≈ 0.95–0.98. If in doubt, use 0.8 as a conservative estimate.

Can kVA ever be less than kW?

No. kVA is always greater than or equal to kW. Since the power factor is always ≤ 1, dividing kW by PF always yields a result equal to or larger than the original kW value. The two are equal only when PF = 1.0 (purely resistive load).

Does this calculator work for three-phase systems?

Yes. The relationship kVA = kW / PF is the same for both single-phase and three-phase systems when expressed in kW and kVA totals. Phase-specific calculations (using amps and volts per phase) are handled by the Amps to kVA calculator.

Kilowatts to kVA Calculator

Convert real power in kilowatts (kW) to apparent power in kilovolt-amperes (kVA) by entering the power factor.

Power Parameters

Real Power (kW)

Power Factor (0.01 – 1.00)

Presets:

Result

Enter values and press Calculate

Formula Reference

kW to kVA

kVA = kW ÷ PF

PF = power factor (0.01 – 1.00)

Reverse: kVA to kW

kW = kVA × PF

Real power is always ≤ apparent power

Result copied!

Summary

This calculator converts real power in kilowatts (kW) to apparent power in kilovolt-amperes (kVA) using the power factor (PF). The formula is S(kVA) = P(kW) / PF, where the power factor is a dimensionless value between 0 and 1 representing how efficiently the circuit converts electrical power into useful work. It is commonly used for sizing generators, UPS systems, and transformers in AC electrical systems.

How it works

Enter the real power in kilowatts (kW).
Enter the power factor as a decimal between 0.01 and 1.00 (e.g. 0.85).
Click Calculate to apply the formula: kVA = kW / PF.
The result shows apparent power in kVA along with a full breakdown.
Use the Reset button to clear all fields and start over.

Use cases

Size generators and UPS systems for a given real power load.
Determine the apparent power rating of transformers.
Plan electrical service capacity for commercial or industrial facilities.
Convert motor nameplate kW ratings to kVA for switchgear selection.
Estimate kVA requirements when power factor is known from utility bills.
Cross-check equipment specifications during electrical system design.
Compare apparent power across different power factor scenarios.
Prepare load schedules for new construction electrical designs.

Frequently Asked Questions

Last updated: 2026-05-23 · Reviewed by Nham Vu