THD In Light Bulbs

Summary:

• If you have no dimmer on the line, then the incandescent bulb will inject less noise.
• If you have a dimmer on the line, but the dimmer is on full, the LED will likely inject more noise. It will depend on the dimmer and LED bulb.
  
• If you have a dimmer on the line, but the dimmer is not on full, the LED bulb will inject more high frequency noise, but the incandescent bulb will inject more low frequency noise (as it will be drawing 5-6x the power). I can't comment on how your specific equipment will behave.

Unfortunately there are no absolutes, but this is about as good a guideline as can be given.

Thank you @audiozenology. That summary was all I needed.

 My television and computer monitor are full of LEDs...oh well.

If it wasn't LEDs it would be compact fluorescents or vacuum tubes. They would use more power and there would be even more noise. LEDs are not noisy, just the power supplies used to drive them.

There is more to electronic noise than the THD.   Power factor also comes into play.   The OP's bulbs  seem to be pretty good with a Power Factor >.90.   Many of the cheap ones are not Enerystar rated have a power factor ~50%.   That means that half of the power going in is wasted and the unused "power" is dumped into the neutral leg.  And while the THD: <35% does not sound that good hopefully it is much <35%.  A good bulb can be ~ 10%.   But generally if a good manufacturer cares about their design power factor and THD are both optimized.    


So the take home message is you should look up the specs before you start swapping out your incandescents and don't buy the cheapest dollar store brand bulbs.

No, that is not what it means. A power factor <1 simply means that current and power are out of phase. This does not mean that there is "wasted power". Power factor does not give any definitive indication of wasted power.

That means that half of the power going in is wasted and the unused "power" is dumped into the neutral leg.

Power factor can give an indication of the potential for noise (in the form of THD), but only if you know the circuit. The THD of up to 35% is the important figure of merit in this case. It is unlikely to be << 35% or they would have just used a lower number in their marketing.  At this low power level, power factor will not have any appreciable impact on other equipment but the noise from high THD may.