LED Tip 4: What you need to know about Power Factor

The Power Factor (PF) of a LED light or driver indicates the ratio of real power used. This is the amount of watts used by the light compared to the apparent power drawn into the lamps circuit. So why does this matter?

PF provides a measurement of how close your load is to that of an incandescent bulb, which has a PF of 1. Historically, incandescent bulbs have had near perfect power factors. All LEDs and drivers are measured against this base line.

A low power factor is also a sign of an inefficient product or light as it draws more current into the circuit than is utilized by the load. In other words, while you think you may be only consuming 100W of energy, you actually may be consuming significantly more because of the fixtures bad PF ratio.

When choosing LED fixtures or fixture conversion units with higher power factors, it minimizes the current capacity of components in your lighting circuit. This includes dimmers and cables as the product is not drawing an excessive amount of current compared to what is required.

  • The lower the current draws (higher power factor) of LED product, the more LED lamps that can be supplied by one circuit.
  • A poor PF score means you are using more energy than you may realize.

A Practical Example

100W LED fixture with a PF of 0.5: 100W ÷ 0.5 = 200W (actual) consumption
100W LED fixture with a PF of 0.8: 100W ÷ 0.8 = 125W (actual) consumption

Are there other problems associated with a low Power Factor Score?

  • Power is recycled from the LED Fixture to the power source, creating a disturbance.
  • Harmonics from the LED fixture degrade the line and affect the performance of other equipment on the same circuit.

So what ideally is the target PF you should look for?

Realistically, .85 is a good target. Many of the products we offer at MyLEDLightingGuide.com are in the .90 to .95 range.

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