The ratio of the real power flowing to the load to the apparent power in the circuit. Where the voltage and current are in phase, the wattage drawn is simply the product of the two. However in led the voltage and current are slightly out of phase meaning that more current is drawn than the wattage suggests. Thus the product of the voltage and current is greater than the wattage. Power factor (PF) is defined as watts/volts x amps. Many led luminaires and retrofits are designed to have a power factor > 85%. Poorer quality retrofits an have power factors of 50% and thus draw twice the current the wattage would imply.