Low Power factor of CFL and LED lamps (bulbs)


Senior Member
I was reading an article that was talking about the power factors of these bulbs that are thought of as efficient and was surprised when the article was talking about power factors being as low as .25

It said the power factor, at least on the LED bulbs, was dependent on the manufacturing process and the quality of the electronics used.

For context, this article was related to doing a load analysis for an off-grid system. It was promoting the use of more efficient loads to decrease the size of the system requirements, but then stated that a power factor "adder" had to be included for low power factor loads such as these bulbs that have a power factor in the .25 - .75 range.

I was surprised when it described this low power factor.
Anyone know about this?


Senior Member
Fort Collins, Colorado
Electrician, Contractor, Inspector
190211-2216 EST


Buy a CREE LED bulb and check its power factor. 9.9 W PF = 0.96 .


Have you ever checked Phillips A19 style dimmable lamps for PF? I wish manufacturers were required to state this as with some it could get you in a bind if you had, say, a .5 PF lamp
and didn't plan accordingly. Or maybe low PF is a thing of the past with most quality LED replacement lamps?


Electron manager
NE Nebraska
Not that this doesn't still create problems, but this PF is from harmonic distortion and isn't the same thing as PF of a motor which is displacement power factor.

A 20 watt lamp with .50 PF is contributing totally different level of issues to the system than a 10 kVA motor running at .95PF also.


Senior Member
190213-1240 EST

Two CREE and one Ecosmart were above 0.96 PF, an EarthBulb free from DTE was 0.72 PF.

Close to 1 PF means that the current waveform has to be close to a sine wave.



Staff member
San Francisco Bay Area, CA, USA
Electrical Engineer
Distortion PF is often not read correctly by meters designed to only look at the fundamental frequency.

To me the entire thing is irrelevant though. Why would anyone care what the PF is of an LED bulb? 100 13W LED bulbs is only 1.3kW, not enough to make a difference in anyone's bill even if it WERE a commercial or industrial facility getting charged for PF. If it's residential, nobody cares, or needs to.


Staff member
Note the OP did say "off grid system". I am not sure how PF effects inverter efficiency.
Similar to a generator, in that the inverter output stage needs to be able to handle the full current while the input stage needs to source just the current corresponding to the actual power. To the extent that the output current and associated resistive losses are higher than they would be, the low power factor will reduce efficiency. The higher the basic efficiency, the lower the effect of low PF.
The harmonic distortion creates uneven currents in the neutral conductor, this reducing the efficiency of a balanced 3-phase system. These types of problems can lead to increased voltage drop and overcurrent in the neutral.