What are the benefits?
Compact fluorescent light bulbs (CFLs) use less electricity, last longer, and are better for the environment than conventional incandescent light bulbs.

How long will they last?
Compact fluorescent light bulbs are generally rated to last from 6,000 to 15,000 hours, with most having an expected life of 10,000 hours. Used for 5 hours per day, this is equivalent to 4 to 8 years of use. In comparison, typical incandescent light bulbs are usually rated to last from 800 to 1,000 hours. Actual lifetime will be affected by the frequency of on-off cycles, and the operating environment. More frequent on-off cycles and using the bulb in extreme cold or hot environments will result in shorter life. This does not mean CFLs should be left on when not needed in order to get a longer life. The increased operating cost will generally exceed potential deferred replacement cost savings.

Where should I use spiral bulbs?
Spiral bulbs generally offer the most light for the least money. They are more likely to fit in common light fixtures than other styles. Use higher wattage bulbs in shaded table and floor lamps, and lower wattage spirals in multi-socket ceiling fixtures.

Where should I use capsule bulbs?
Globe and A-style bulbs look similar to their incandescent counterparts. Use these types of bulbs in fixtures where the bulb is visible, such as bath vanities, mini-pendants, or fixtures with clear diffusers. Capsules will tend to not produce as much light per watt than spiral bulbs.

Can "regular" CFLs be used in dimmable/3-way fixtures?
No. Only use dimmable compact fluorescent bulbs in fixtures with a dimming control, and only use three-way bulbs in fixtures with a three-way switch. Using regular CFLs in these types of fixtures will cause premature product failure and may represent a fire hazard.

Can compact fluorescents be used with timers, motion sensors, and photocells?
It depends on the control. In general, they will work fine with mechanical timers, but may not work properly with electronic timers/switches that draw current continuously, motion sensors/photocells that "leak" current when turning on, or controls that have a minimum load rating higher than the wattage of the compact fluorescent.

What do terms like T8, G25, PAR38, A19, and so on mean?
These identify the style and size of the bulb or lamp. The alpha character represents the style. The numeric value represents the diameter (in 8th's of an inch). An A19, therefore, is 19 eights of an inch wide, which means it is 2 3/8ths of an inch wide. Common style codes include G=globe, T=tube, R=reflector, PAR=parabolic aluminized reflector, ER=ellipsoidal reflector, A=common light bulb shape.

What should I do when they stop working?
While compact fluorescent light bulbs are usually accepted by municipal landfills and trash haulers, CFLs contain small amounts of mercury, a toxic metal that should be kept out of the waster stream. Ideally, recycle your expired CFLs be taking them to a household hazardous waste collection event, or through a CFL recycling service.