Difference Between Active and Reactive Power

What is Active Power?

The power employed in an Alternating Current circuit is associated with active power. This circuit can be described using terminologies such as true power, actual power or active power. This is calculated in kilowatts (kW) or megawatts (MW). It is the real output of the electrical system that drives the electric circuits or load.  

Active power is calculated in all circuits by measuring how much power is squandered by the circuit. Active power could be found in both alternating current and direct current circuits. This power originates when the current and voltage are in phase. Since it can be visible and measured, it is referred to as actual power.

The letter ‘P’ is used to signify active power. P=V I cos is the active power equation, wherein it is the angle between the phase of the current and voltage. The active power is seen when the current and voltage are in phase, which happens when the angle is 0 or 180 degrees. Electrical energy is converted into several different forms of energy through active power. For example, it can be converted to fluorescence, as in a light source, or electrical energy can be converted to optical energy, and so on. A toaster, coffee machine, heater, and other similar equipment operate on this concept.

What is Reactive Power?

The amount of power required by magnetic devices such as a  motor, transformer and relay to create magnetizing flux is known as reactive power. It flows back and forth, indicating that it goes in both directions through the circuit. While offering no substantial efficiency, reactive energy overloads cables, generators and transformers. However, because it is reflected in the bill, it might significantly raise the overall amount one pays. The reactive power is calculated in kilovolt-ampere reactive (kVAR) or millivolt-ampere reactive (MVAR).

Reaction power is the outcome when the power is out of phase with the voltage in an alternating current (AC) circuit. This is most noticeable whenever the current is out of the phase with the voltage by 90 degrees. This reactive power is two-way. In other words, it travels from the originating source to the load and from the load to the emerging source.

Reactive power isn’t expressed in Watts, even though it is a form of power. It is frequently expressed as ‘var.’ in AC power networks. The character ‘Q’ is used to represent reactive power. Q= V I sin is the equation for calculating reactive power.

Difference Between Active and Reactive Power

  1. Active power is the energy that travels from the origin of emergence to the load. In contrast, reactive power is the energy that travels from the origin of emergence to the load and back to the source after that. 
  2. Active power is the amount of energy consumed by the load. Reactive power, on the other hand, is a pointless power.
  3. The real power is determined in Watts (W) and is referred to as active power. In contrast, reactive power can be calculated in VAR.
  4. The letter P signifies active power, whereas the letter Q signifies reactive power.
  5. Active power is utilized in alternating and direct current circuits, while reactive power is exclusively used in alternating current circuits.
  6. Active power transforms electrical energy into various forms of energy, whereas reactive power generates electric flux within a circuit instead of converting it.

Comparison Between Active and Reactive Power

Parameters of ComparisonActive PowerReactive Power
DefinitionActive power is a power that travels consistently between the source to load within an electric circuit.In an electric circuit, reactive power is defined as a power that travels continuously between the source to load and then back to the source.
The consonant, ‘P’ signifies active power.The consonant ‘Q’ signifies reactive power.
The Direction Of Power FlowConcerning time, Active power flows in just one direction.In terms of time, this power works in both directions.

Active power may be used in both AC and DC circuits.Reactive power operates in an alternating current (AC) circuit.
FormulaP = V(Voltage) x I(Current) x Cosθ Q = V(Voltage) x I(Current) x Sinθ
UsesActive power is utilized to transform electrical energy into various types of energy.Reactive power does not easily convert but instead generates electric flux in the circuit.


  1. https://ieeexplore.ieee.org/abstract/document/7833212/
  2. https://www.sciencedirect.com/science/article/pii/S0378779608000965