Reactive power is typically quantified in units of volt-amps reactive or VARs, kilovolt-amps reactive or kVARs, or megavolt-amps reactive or MVARs.
Some electrical equipment, most notably motors and fluorescent lights, needs some reactive power to provide the magnetic fields that make them operate, while other equipment such as incandescent lights and heaters do not. This means that motors and fluorescent lights consume reactive power as well as real power.
For this reason the power supplier must supply this extra reactive power in addition to real power. From a physical standpoint, the coils of wire or windings in motors and fluorescent lights slow down the electrons in the circuit, and the result of this process is called reactive power. Loads that require both real and reactive power are called inductive loads.
To manage voltage on their systems, distribution and transmission operators must match the amount of reactive power injected to the amount of power withdrawn from a grid. Reactive power can be injected by many generators, by other devices such as capacitors, and by smart inverters and controls on many battery storage systems.