What is reactive power?

Reactive power is a quantity that is normally only defined for alternating current (AC) electrical systems.
This power goes up and down around some “average” value – this average value is called the “real” power and over time you pay for this in kilowatt-hours of energy. If this average value is zero, then all of the power being transmitted is called “reactive” power.

Reactive power is energy circulating back and forth between the source and the load. Usually, the load is an induction motor. Energy stored in the motor’s magnetic field is transferred to and from the source every time the polarity of the magnetic field reverses. Alternatively, the energy can be transferred to and from power factor compensation capacitors. That transfer of energy is reactive power.

  • Reactive power is the part of the power, which is not utilized by the consumer.
  • It is taken during switching on and fed back to the supply when switched off.
  • Even if the consumer is not utilizing the reactive power, the consumer has to pay for that power.
  • Reactive power is caused by energy storage components are an example :


  • Capacitors can be considered as positive stores of energy.


  • Inductors can be considered as negative stores of energy.

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