Few consumers are aware of the existence of compact fluorescent bulbs. In general, the view of fluorescent lights is limited to the older models, common in industrial and school settings, as well as many kitchens, that offered a fairly "cold" looking light, often accompanied by flickering and buzzing.

Compact fluorescents use one-quarter to one-third as much electricity to give the same light output as a standard incandescent bulb while creating much less heat, and last up to 10 times as long as a standard incandescent light (10,000 vs. 1,000 hours). They are much closer in color to incandescent lighting (although some people are still bothered by the color, at least initially), and generally do not have the buzz or flicker associated with traditional fluorescents. Because of their efficiency they have become a central component of energy conservation programs.

Compact fluorescents are more expensive than incandescent bulbs, although their life cycle costs are much lower. As more consumers become aware of them and there are more places from which to purchase the bulbs, we can expect their popularity to increase and their costs to decrease.

Compact fluorescent bulbs contain two main parts: a lamp and a ballast. The lamp is filled with mercury gas that is ionized by electricity passing through it and generates ultraviolet light. The ballast converts ordinary household voltage to the high voltage needed to ionize the gas in the lamp and limits the amount of current that flowing through. Traditional fluorescent bulbs and older compact fluorescents use magnetic ballasts which consist of loops of wire tightly wound around an iron core. Lamps with magnetic ballasts will flicker briefly when turned on. Most newer compact fluorescent bulbs use solid-state electronic ballasts which operate the lamp at a much higher frequency, start up more quickly, are not as heavy as the magnetic ballasts, and generally do not cause buzzing or flickering. Compact fluorescents and ballasts can be purchased separately (modular) or as an integral unit. The integral, or "self-ballasted" units are less expensive and more readily available. The advantage to buying ballast and bulb separately is that the ballasts have lifetimes 5 to 7 times longer than that of the bulb.

There are several different sizes and shapes of compact fluorescent bulbs. Generally they consist of phosphor-coated tubes, folded or curled to increase the surface area. Quad tube lamps have two u-bent sections and tend to have higher output than single tube models. Triple tube models have three tube sections to give higher light output from a shorter bulb. Sometimes you can see the tubes; on other lamps they are enclosed in a glare reducing casing (cylindrical or globe-shaped) that makes them look more like large incandescents. The newest style bulb uses a spiral shape to maximize light area, with the added benefit of being extremely attractive. The initial manufacturer of this style is GE, which calls it the Heliax.

All of these come in models that can screw into existing incandescent sockets, often with a separate adapter. However, the efficiency is often greater if a compact fluorescent uses a fixture specially designed for the bulb's shape, size and temperature sensitivity. Because compact fluorescent bulbs tend to be bigger and heavier than the incandescents they replace, ordinary incandescent fixtures are sometimes too cramped for them. The extra weight of compact fluorescents may make some standing lamps too top-heavy or unbalance hanging fixtures. Newer compact fluorescents with electronic ballasts are smaller and lighter than magnetic models. You will need to choose the shape and size of a new compact fluorescent bulb based upon the fixture's dimensions. If a fluorescent is too large to fit inside a lamp shade harp (the metal bracket that holds the shade above the bulb), harp extenders can be purchased that will solve the problem by both widening and heightening the space available for the bulb. One problem with harp extenders, however, is that they raise the lamp shade, which may partially expose the lamp to view. A circular compact fluorescent may be the solution if the double or triple tube models are too tall for a lampshade. The harp fits between the ballast and the circular lamp. However, you may still need harp extenders to widen the space for the ballast. This "Circline" style is not technically a "compact" fluorescent. It's more like a linear tube bent into a circle. Circlines may have poorer color rendition but are available with higher light output then most true compacts fluorescents, making it easier to replace incandescents of 100-watts or greater. Generally, you cannot use a compact fluorescent in a light that has a dimmer switch, although this technology is not far away.

Even if a compact fluorescent and an incandescent bulb have the same rated lumen output they may produce different amounts of light, depending on the shape and color of the lamp shade or fixture. In general, light from fluorescents tends to be more diffuse than that from incandescents. Also, the light output from many compact fluorescents decreases when they are installed base-down instead of base-up. This means that if you put a compact fluorescent bulb in a ceiling fixture hanging down, it may emit more light (lumens) than if you put the same bulb in a table lamp. The base-down lamp will still be more efficient than an incandescent, but you may need a higher-wattage compact fluorescent than you would choose based on a simple comparison of rated lumen output. Circlines and certain shapes of compact flourescents are less likely to have this problem. Manufacturers are required to indicate whether the position of the bulb affects its light output. As a final note of caution: all fluorescent lights contain small amounts of mercury. The mercury poses no threat while it's in the bulb, but it does represent an environmental hazard. If you break a bulb, avoid inhaling the mercury and use a wet rag to collect the debris immediately.

The table below lists many of the common sizes and styles of compact fluorescent bulbs and where they may be used.

Linear Fluorescents
For many home lighting needs the most efficient light for the job is still the older style linear fluorescent. Many people use them in bathrooms, kitchens, and garages because a single fixture can illuminate a relatively large area. The most common of these linear fluorescents is the 4-foot T12 (T12 signifies a lamp tube 12-8ths of an inch, or one and a half inches, in diameter) that we associate with offices. T8 lamps (one inch in diameter) are more efficient; they use electronic ballasts, are narrower and most have better color rendition than the T12s. They reduce energy consumption by about 50%. To replace a T12 lamp with a T8, you must buy a special ballast; for the highest efficiency, use an electronic ballast. T5 linear lamps can be mounted under cabinets or over sinks for efficient task lighting. All linear fluorescent fixtures need to be hard-wired by an electrician.