Some peoples recommend using small LED or CFL lamps in home rather than using big lamps, because they has better Power factor than big lamps,

For example if you need 80 W Lamp in your room, it is better to using 10 lamps (each 8w) rather than using one 80 W.

Already i test a small 9 W CFL and the power factor was 0.8, then i test 50W CFL and its PF was only 0.57,

So can we say always small LED or CFL lamps has better PF? If yes, Why?

  • \$\begingroup\$ Regardless of WHY, why do you care? It can be important if you are concerned with waveform distortion or noise or are powering them with an inverter or similar, but in most applications power factor does not affect electricity costs and does not cause problems in its own righjt. (eg PF may be due to a very peaky power draw that causes interference but that's not due to PF per se.) \$\endgroup\$
    – Russell McMahon
    Commented Mar 28, 2017 at 11:43
  • \$\begingroup\$ Because of the way the traditional spinning disk electric meter works it effectively does not "count" the electricity you use that has a low power factor..i.e. 90 degrees out of phase. Not so sure that is still true with modern meters. Consequently, the electric company is rather keen on their customers having a PF of 1. Especially commercial users that use A LOT of power. I'm rather surprised to hear that LED lamps have such poor PFs, I would have thought there would have been regulatory laws governing that by now. \$\endgroup\$
    – Trevor_G
    Commented Mar 28, 2017 at 12:59

1 Answer 1


The Power Factor (PF) by itself does not relate to the type of lamp be it LED or CFL or even a oldfashioned lightbulb.

But ! Everyone knows that a lightbulb has a very good power factor of 1 !

Yes the bulb itself does but suppose I use a 110 V bulb on 240 V and I use a large inductor or a capacitor to drop that 240 V to the 110 V the lamp needs. Now the PF will not be 1.

It is the same with CFL and LEDs, depending on how I change the voltage to suite the lamp itself, be it CLF or LED, the PF will be different.

A LED lamp with a capacitive dropper will have a worse PF than LED with an electronic power adapter.

Often CFLs need an inductor for startup and operation. This results in a bad PF. Some CFLs use an electronic converter resulting in a better PF.

So saying that many smaller lamps are better than one large one of the same power regarding PF is nonsense.

Ten 8 Watt LED lamps with a capacitive dropper will give a worse PF than one 80 W LED lamp with a PF optimized electronic converter.

It depends on how the voltage conversion is implemented, not the power rating of the lamp.

And as Russell comments, you should not care about the Power Factor. You only should when you're a heavy / industrial user and have many motors etc rated in kiloWatts. Below 1 kW, usually no-one cares.


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