Disadvantage of low Power Factor 

We know that 

 P = V I cos φ, 

for particular amount of power at constant voltage, Power (P) and voltage (V) in the above expression of power are regular, so

  I  ∝ 1/cos φ

From the above relation it is clearing that current is inversely proportional to the power factor of the load. Thus low power factor results in higher current, more losses, more voltage drop, greater size of conductor and high rating of the equipments used in the power system.