Enter the true power and the apparent power into the calculator to determine the reactive power.

**Related Calculators**

## Reactive Power Formula

The following formula is used to calculate an reactive power value.

RP = SQRT ( AP^2 – TP^2)

- Where RP is the reactive power
- AP is the apparent power
- TP is the true power.

## Reactive Power Definition

A reactive power is the amount or proportion of power that is out-of-phase with the other transmitting powers, known as the true power and apparent power.

## Is reactive power good or bad?

In general a reactive power will be good for an electric system. The reactive power provided to or by the system is used to regulate the voltage of a system. For example, if the voltage is not high enough in a system then the active power may not be supplied. A reactive power is then introduced to increase the voltage and allow the active power to transfer and do work.

## How does reactive power affect voltage?

In general, an increase in reactive power is accompanied by an increase in voltage, and a decrease in reactive power is accompanied by a decrease in voltage. Depending on the system, these may not hold true, but for the majority of currents this does apply.

## Does DC have reactive power?

By definition a reactive power is a byproduct of an alternating current where the voltage and current are out of phase. As a result a DC current does not have or required a reactive power component.

## Can a reactive power be 0?

Reactive power can be zero when the phase angle between the voltage and current is the same. In these cases, the system is said to have a power factor unity. In these types of electrical systems, only real power is consumed by the circuit.

## Reactive Power Example

How to calculate a reactive power?

**First, determine the apparent power.**Calculate the apparent power.

**Next, determine the true power.**Calculate the true power.

**Finally, calculate the reactive power.**Calculate the reactive power using the equation above.

## FAQ

**What is reactive power?**

A reactive power is the total power, known as volts times amperes, that are out-of-phase with each other. It’s the portion of electricity that sustains the electric and magnetic fields needed for alternating current equipment.