AC loads split into real kilowatts and reactive kVAR—power factor links them to apparent kVA. This guide walks through the power factor and reactive power calculator: kVA, PF as a decimal, and the reactive component your breakers still see.
Benefits
- kW = kVA × power factor; kVAR = √(kVA² − kW²).
- Outputs kW, kVAR, kVA, PF, and phase angle φ together.
- Motor PF often 0.7–0.9; resistive loads near 1.0.
How it works
- Enter apparent power in kVA from equipment plate or load study.
- Add power factor (0–1)—measured or typical for motor vs. resistive mix.
- Read reactive kVAR plus real kW—size on kVA, budget on kW.
FAQ
How do I calculate reactive power from power factor?
kW = kVA × PF, then kVAR = √(kVA² − kW²). Example: 12 kVA at 0.85 PF → kW = 10.2 → kVAR = √(144 − 104.04) ≈ 6.32 kVAR. Lower PF means more kVAR for the same kVA.
What is the difference between kW, kVAR, and kVA?
kW is real power (useful work). kVAR is reactive power (magnetizing/inductive exchange). kVA is apparent power—the vector sum: kVA² = kW² + kVAR². Conductors and transformers are limited by kVA and current, not kW alone.
Why does poor power factor matter for inverters?
An inverter rated in kVA must supply both kW and kVAR demanded by the load. A 10 kW motor at 0.75 PF may need ~13.3 kVA apparent—exceeding a 10 kVA inverter even though real power fits. Calculate kVAR before assuming wattage equals sizing.
Technical specifications
- kW = kVA × PF.
- kVAR = √(kVA² − kW²).
- PF = kW ÷ kVA; φ = arccos(PF).
- Related: kva-to-kw, inverter-sizing, amps-to-watts.