What is reactive power?

Reactive power refers to the power that oscillates between the source and the load in an alternating current (AC) system. This occurs in circuits that include inductive or capacitive components, such as motors or transformers, where energy is temporarily stored and then returned to the source. Rather than doing useful work, this power is essential for maintaining the voltage levels necessary for the system's operation, ensuring that it functions efficiently and reliably.

Understanding reactive power is crucial for HVACR systems, as many components rely on it for their operation. Unlike resistive power, which does actual work (like heating the elements in a heater), reactive power helps establish electric and magnetic fields that enable the overall system to operate effectively. In energy calculations, reactive power is measured in volt-amperes reactive (VAR), contrasting with active power, which is measured in watts (W) and represents the power actually consumed for useful work.

The other options refer to concepts not directly related to the definition of reactive power. The power lost in resistance relates to resistive losses, which are not the same as reactive power. A constant power in a circuit indicates steady-state operation, while total power includes both active and reactive components, making it different from the specific nature of reactive power itself.