What happens if I use a screw-in CFL with a dimmer?

Using CFLs with dimmers is a terrible idea. It’s like watching two people with competing interests and techniques trying to work on the same project. A CFL-dimmer combo will result in severely limited light levels, no response to the dimmer switch or flickering lights. CFLs are limited by the size of their ballasts. They are generally too small to fit in the needed dimming components but just right to fit inside the base of the bulb. Incandescent bulbs, although more energy-thirsty, do not require a ballast to function. A balancing element to using incandescent bulbs is that purely by dimming their lights, the homeowner or renter can save on energy usage and monthly costs. In the long run, your light bulb can last up to ten years because of dimming. It is one of the simplest, greenest, most cost-effective things to do for your home.

In addition to this, there are CFL manufacturers who are trying to bridge the gap to dimming. There are brands like Neptune who have recently developed a line of CFLs capable of dimming. Before committing yourself to buying more than necessary, purchase one to test. Gauge for yourself whether it meets your dimming standards.

Source: Lutron