Power Factor

Power factor is characteristic of alternating current (AC) circuits. Always a value between (0.0) and (1.0), the higher the number the greater/better the power factor.

Circuits containing only heating elements (filament lamps, strip heaters, cooking stoves, etc.) have a power factor of 1.0. Other circuits containing inductive or capacitive elements (ballasts, motors, personal computer, etc.) usually have a power factor below 1.0.

Normal power factor ballasts (NPF) typically have a value of (0.4) - (0.6). Ballasts With a power factor greater than (0.9) are considered high power factor ballasts (HPF).

The significance of power factor lies in the fact that utility companies supply customers with volt-amperes, but bill them for watts.

The relationship is (watts = volts x amperes x power factor). It is clear that power factors below 1.0 Require a utility to generate more than the minimum volt-amperes necessary to supply the power (watts).

This increases generation and transmission costs. Good power factor is considered to be greater than 0.85 or 85%.

Utilities may impose penalties on customers who do not have good power factors on their overall buildings.

Watts, or real power, is what a customer pays for. VARS is the extra “power” transmitted to compensate for a power factor less than 1.0. The combination of the two is called "apparent" power (VA or volt-amperes).

Consider this popular analogy to clarify the relationship between real and apparent power.

We all know a glass of draft beer generally has a "head" on it. Let's say your favourite pub institutes a new policy - you only pay for the beer, not the foam. While the foam is just aerated beer, it is not really usable in that form.

If the glass of beer is half foam, you pay half the price.

This is the same principle as electricity generation - the consumer only pays for the beer (real power), not the foam

(The "VARS" mentioned above).