Calculate power factor from real power and apparent power.
Power factor is the ratio of real power (the power actually doing useful work, in kW) to apparent power (the total power the system supplies, in kVA). A power factor of 1.0 means all supplied power is being used effectively.
Formula: PF = Real Power ÷ Apparent Power. The difference between the two is reactive power, which flows back and forth in the system without doing useful work but still takes up capacity.
Low power factor is a real cost issue for commercial and industrial electricity customers — many utilities charge penalties below a threshold like 0.9, since it means the utility has to supply more current for the same useful output.
A facility drawing 8kW of real power with 10kVA of apparent power has a power factor of 0.8, or 80%.
Inductive loads — motors, transformers, fluorescent ballasts — are the most common cause, since they draw reactive current in addition to real current.
Power factor correction capacitors are commonly installed to offset inductive reactance, bringing the ratio closer to 1.0 and often reducing utility penalty charges.
Rarely directly — most residential meters don't bill for it. It's primarily a commercial and industrial billing consideration where usage is large enough to matter to the utility.