A capacitor is an electronic component typically used to "clean up" the flow of electricity by insuring steady, consistent wattage through a circuit or part of a circuit. A capacitor is actually a type of battery, but differs from a storage battery in that it is not designed for long-term storage of energy. Capacitors temporarily absorb extra power that may bleed into the system and can release stored energy back into the system as power levels normalize.

Capacitors in electrical systems improve efficiency by reducing energy losses in transmission and distribution systems. Large capacitors are installed in substations and much smaller capacitors can be seen on poles carrying high-voltage lines, and their energy capacity is rated in megavars and kilovars. Capacitors are used in a vast array of electrical and electronic circuits, and are essential components of everything from CD players to hair dryers. Their energy capacity is dramatically lower, typically measured in microfarads (practically speaking, a farad is roughly equivalent to a var), or trillionths of the capacity of large transmission capacitors.

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