Difference Between Active and Reactive Power (With Table)

In electrical circuits, power is defined as the sum of voltage and current. It is the pace at which electrical energy is carried through electric circuits in technical words. Active power and reactive power are the two most often used concepts to represent the movement of energy in electrical power networks. These two subjects are crucial in physics. This topic is essential in all disciplines of engineering.

Active vs Reactive Power

The main difference between active and reactive power is that active power is indeed the actual power used by the circuit. Reactive power, on the other hand, is a power that is pointless since it only passes between the source and the load. The active power is one-way, but the reactive power is two-way.

Active power is the power that is utilized and generated in an alternating current or direct current circuit for a specified purpose. Real Power, True Power, Usable Power, and Watt-full Power are other terms for it. It is represented by the letter “P” and is measured in kilowatts, Watts, or Megawatts.

Reactive power is simply defined as the power that flows between both the source and the load within a circuit. It is also sometimes termed as Watt-less Power or Useless Power. The character “Q” denotes reactive power, which again is assessed in Volt Ampere Reactive, kVAR or  MVARs.

Comparison Table 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 FlowWith respect to 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.

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. When the current and voltage are in phase, which happens when the angle is 0 or 180 degrees, the active power is seen. Electrical energy is converted into a number of different forms of energy through active power. It can, for example, 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).

When the power is out of phase with the voltage in an alternating current (AC) circuit, reactive power is the outcome. 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, despite the fact that 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.

Main Differences Between Active and Reactive Power

  1. Active power is the energy that travels from the origin of emergence to the load, while reactive power is the energy that travels from the origin of emergence to the load and thereafter back to the source. 
  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 both alternating current 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.


There are indeed 3 major categories of power in both Ac power and DC power circuits. Active power, reactive power and apparent power are the three types of power. To summarise, perceived power is the summation of active and reactive power.

Some of these powers are quantifiable but not rationally described. As a result, active power is regarded as real power. The active power throughout the circuit does beneficial work. The reactive power, on the other hand, just passes all across the circuit, doing no constructive activity. The symbols, formulae, and definitions of active and reactive power are given to dispel misconceptions about these forms of power in engineering and physics.


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