You often know real kilowatts from a motor plate or meter—not kVA. This guide shows the real power (kW) to reactive power (kVAR) path: convert kW and PF to apparent kVA, then read kVAR from the power triangle in the calculator.
Benefits
- Bridge: kVA = kW ÷ PF, then kVAR = √(kVA² − kW²).
- Direct form: kVAR = kW × tan(arccos PF) when PF is known.
- Confirms kW output matches your known real load.
How it works
- Start with real power kW (nameplate shaft power ÷ efficiency, or measured kW).
- Divide by power factor to get kVA: kVA = kW ÷ PF.
- Enter that kVA and PF in the tool—read kVAR and verify kW matches input.
FAQ
How do I convert kW to kVAR with power factor?
kVA = kW ÷ PF, then kVAR = √(kVA² − kW²). Example: 9 kW at 0.85 PF → kVA = 9 ÷ 0.85 ≈ 10.59 → kVAR = √(112.1 − 81) ≈ 5.58 kVAR. Equivalently kVAR ≈ kW × tan(arccos 0.85) ≈ 5.58.
I only have kW on the motor—what PF do I use?
Use motor catalog PF at full load (often 0.8–0.9) or measure at the panel. Underestimating PF underestimates kVA and kVAR—size conservatively for distribution. Resistive loads: PF ≈ 1 → kVAR ≈ 0.
Why convert kW to kVAR if billing is in kW?
kVAR does not appear on a simple energy bill but sets apparent kVA and current. Inverter limits, transformer loading, and conductor ampacity follow kVA = √(kW² + kVAR²). Converting from known kW completes the triangle for equipment sizing.
Technical specifications
- kVA = kW ÷ PF.
- kVAR = √(kVA² − kW²) = kW × tan(arccos PF).
- PF = kW ÷ kVA (reverse check).
- Related: kva-to-kw, calculate-kvar-for-inverter-and-conductor-sizing.