Dimmer Switches: A Bad Idea for CFLs or Incandescents
One of the big complaints that we have heard about compact fluorescents is that they are not dimmable. Our first reaction was, why do you have dimmers anyways? Historically, incandescent dimmers worked through resistance- they lowered the voltage and the dimmer switch got hot, and the light bulb became very inefficient as low voltage barely warmed the filament. The bulb lasted forever but it used as much electricity as if it was running full blast.
Then the electronic dimmer was invented, which work by turning the light bulb on and off faster than we can see it, 120 times a second. It is not 100% efficient, which is why dimming your lights 25% reduces your electricity consumption only 20%. And it is no wonder why it causes problems for compact fluorescents, which are not designed for this additional turning on and off of a switch 120 times per second.
A more efficient way to vary lighting conditions is to have different circuits; in our house we have two switches in the dining room, one for the central focus on the table and another for the perimeter of the room.
Conclusion: Dimmers are wasteful for any kind of bulb, so it is hard to be critical of CFLs for not dimming well, neither do incandescents. More info on dimmers from ::How Stuff Works