Before you replace every bulb in your house with CFLs, there are a few limitations. Future technology will improve or eliminate these limitations.
CFLs take a while to warm up and achieve total brightness (including “instant-on” CFLs).
Turning a CFL on and off frequently can shorten its life.
CFLs may be used outdoors as long as it is rated for outdoors and in a fixture. In a cold environment, the bulb may not achieve full brightness. Check the bulb package for the lowest operating temperature. If an indoor rated bulb is used for outdoors, it may not last as long and void the warranty.
For dimming, use dimmable CFLs only and dimmers that are listed for use with CFLs. Check the dimmer and bulb package for compatibility. Dimming range can be limited especially at the low end. Dimmable CFLs are more expensive.
Photocells and electronic timers also need to be compatible with CFLs. Most of the newer photocells and electronic timers are compatible. There are CFLs available with built in photocells. Always check the packaging of a photocell or electronic timer if they are compatible with CFLs.
Garage door openers and ceiling fans usually do not recommend CFLs. There could be vibration issues that could reduce the life of a bulb. The user manual should indicate CFL compatibility with the product.
Do not use CFLs in enclosed (covered) recessed lighting fixtures because of possible overheating.
Compact Fluorescent (CFL) - Compact fluorescent lights (CFLs) are very popular for saving energy, usually about 75% savings over incandescent bulbs.
CFLs for the home have a built-in ballast at the base to convert line voltage to voltage that will light a bulb. Because of this ballast these bulbs tend to be bigger than incandescent bulbs and may not fit well in certain light fixtures or lamps. CFLs may protrude from a ceiling recessed fixture more than an incandescent bulb. These fixtures usually can be adjusted so the CFL sits higher in the fixture.
CFLs may not be as bright as their incandescent equivalent wattage bulb. Check the lumens rating on the package and compare to the lumens chart on the Light Bulb Packaging Info page.