A device has low Power Factor when it draws more current than it uses.


What is reactive power and how is it measured?

Reactive Power (kVArh) is the difference between working power (active power measured in kW) and total power consumed (apparent power measured in kVA). Some electrical equipment used in industrial and commercial buildings requires an amount of ‘reactive power’ in addition to ‘active power’ in order to work effectively.

Reactive power therefore generates the magnetic fields which are essential for inductive electrical equipment to operate – especially transformers and motors.
This load is measured via the reactive register on your half hourly meter.


What is Power Factor and how is it caused?

Power Factor is the relationship between ‘active’ and ‘reactive’ power and indicates how effectively electrical power is being used: Bad power factor - is low (less than 0.95) so more reactive power is required. Good power factor - is high (greater than 0.95) so power is used more effectively. ‘Perfect’ power factor - (1.0) this is known as unity and does not use any reactive power. Most electrical equipment, such as motors, compressors, welding sets and even fluorescent lighting, create an inductive load on the supply. An inductive load requires a magnetic field to operate, which then causes the electrical current to “lag” the voltage - i.e. the current is not in phase with the voltage.