Power Factor Calculator
Utilities charge real power in kW but must supply apparent power in kVA — and when your load is inductive, the gap between the two shows up as a power factor penalty on the bill. Enter your real (kW) and reactive (kVAR) loads to get the power factor, apparent power, phase angle, and the exact capacitor correction needed to reach a target PF.
Load Profile
The Power Triangle
Real, reactive, and apparent power form a right triangle:
S = √(P² + Q²) | PF = P / S = cos(φ)
P is real power (kW) — the work done. Q is reactive power (kVAR) — the magnetizing energy sloshing back and forth in motor and transformer windings. S is apparent power (kVA) — what the utility must size its transformers and wiring for. Power factor is the cosine of the angle between P and S; at 45° it is 0.707, and a 50 kW load draws 70.7 kVA instead of 50.
Typical Power Factors by Load
| Load Type | Typical PF | Impact |
|---|
Values are typical operating ranges. Measure your own kW and kVAR at the service entrance for exact numbers.
How to Use This Calculator (3 Steps)
Case Study
Frequently Asked Questions
What is power factor and why does it matter?
It's kW ÷ kVA. Low PF means extra current for the same work — hotter wiring, less transformer capacity, utility penalties.
How do I calculate PF from kW and kVAR?
S = √(kW² + kVAR²); PF = kW ÷ S. 50 kW + 25 kVAR → 55.9 kVA → PF 0.89.
How much capacitor correction do I need?
Qc = kW × (tan φ₁ − tan φ₂). For 50 kW from 0.89 to 0.95, about 8.6 kVAR.
Leading or lagging?
Inductive loads lag (current behind voltage). Too many capacitors go leading, causing its own problems.
What's a typical PF?
Resistive ≈1.0; uncorrected motors 0.70-0.85; utilities penalize below 0.85-0.90.