Capacitor

The unused power caused by the inductive and capacitive effects of transmission lines or electrical loads using alternating current is called reactive power. Reactive power, also known as virtual power or phantom power, is measured by VAR (Volt-ampere reactive).

Capacitors and supercapacitors are passive components that store energy in the form of an electrostatic field. Although the function of both is to store energy, there are some important differences between them. Supercapacitors can store more charge than regular capacitors and provide energy much faster than a battery.