Power Factor Calculator
Calculate power factor, reactive power, and apparent power for AC circuits. Includes correction capacitor sizing.
Results
Power Factor Ratings
| Power Factor | Rating | Notes |
|---|---|---|
| > 0.95 | Excellent | Ideal; utilities rarely penalize |
| 0.90 – 0.95 | Good | Acceptable for most commercial loads |
| 0.80 – 0.90 | Fair | May attract utility surcharges |
| < 0.80 | Poor | Utilities often penalize; correction needed |
What Is Power Factor?
Power factor (PF) is the ratio of real power (kW) — the power that actually does work — to apparent power (kVA) — the total power drawn from the supply. It ranges from 0 to 1 (or 0% to 100%), where 1.0 means all drawn power is used productively.
The "missing" power is reactive power (kVAR), which is consumed by inductive or capacitive loads like motors, transformers, and fluorescent lights. Reactive power doesn't do useful work but must still be supplied by the utility, increasing current in wiring and transformers.
Why it matters: A low power factor means higher current for the same amount of real work, causing greater resistive losses, overheating, and voltage drops. Many utilities charge large commercial customers a "power factor penalty" when PF drops below 0.85 or 0.90. Adding power factor correction capacitors reduces reactive demand and can significantly cut electricity bills.
Power Factor Correction: Capacitors generate reactive power locally, reducing the reactive current drawn from the supply. The correction capacitor kVAR needed equals: kVAR_corr = kW × (tan(arccos(PF_current)) − tan(arccos(PF_target))).