What is Power Factor (cosφ)?
The ratio of active power to apparent power; it shows how efficiently electrical energy is used.
Power factor (cosφ) is the ratio of the active power (kW) drawn at a facility to the apparent power (kVA), and it shows how efficiently electrical energy is used. A value close to 1 means almost all the power drawn does useful work; a low value means a significant part is wasted as reactive power.
Inductive loads lower the power factor. A cosφ below 0.95 signals that the facility has entered the inductive reactive penalty zone. Distribution companies typically expect a power factor above 0.95; compensation is used to raise this value to the 0.98–0.99 range.
Power factor matters not only for penalties but also for facility efficiency: a low power factor means more current is drawn to do the same work, cables and transformers are needlessly loaded, and losses increase. Monitoring the power factor continuously with an energy analyzer prevents both the penalty and the inefficiency.
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