Power Factor (PF)

Power factor is the ratio of real power (watts) to apparent power (volt-amperes) drawn from the grid, from 0 to 1. A fixture with PF 0.95 draws current almost perfectly in phase with voltage; low-PF equipment draws extra reactive current that heats wiring, loads transformers, and in commercial tariffs can incur utility penalties. Quality industrial LED drivers specify PF ≥ 0.9–0.95 at rated load (regulations such as the EU Ecodesign rules set minimums). PF interacts with THD — both describe how cleanly the driver loads the supply — and matters practically when hundreds of fixtures share a distribution board: cable sizing and breaker selection follow apparent, not real, power.