Power Factor

In AC circuits, current and voltage waveforms may not peak at the same instant. This phase displacement means that while the source delivers apparent power (VA), only a portion performs useful work (W) — the rest oscillates as reactive power (VAr) between the source and inductive or capacitive loads. Power factor is the ratio P/S, ranging from 0 to 1. Induction motors, transformers, and fluorescent lighting are common sources of low power factor, typically 0.7–0.85 lagging. Low power factor increases the current drawn for the same real power output, requiring larger cables and transformers and increasing I²R losses. Utilities penalise consumers with power factors below 0.9 or 0.95 through reactive energy charges. Power factor correction using capacitor banks or active filters reduces reactive current, lowers losses, and frees up network capacity. For non-linear loads with harmonic distortion, the true power factor (including displacement and distortion components) must be considered rather than just the displacement factor cos φ.