Where to Give CFLs the Green Light

CFL advantages notwithstanding, incandescents still shine in a few applications in your home.  Certain other applications will work fine with CFLs, but only if you choose the right type of CFL.

Where to keep using incandescents

As regards safety, see the section FAQs.  If you are ultra cautious about mercury exposure, do not use CFLs or any fluorescent light in a room that infants or other children occupy.  Breakage can expose occupants to a miniscule quantity of mercury vapor.  Use incandescents instead.

Using bare spiral CFLs

The open or "bare" spiral CFLs you find for a buck or three today do a great job in most basic household lamps.  They will light up in most other applications, too, but may be dim, slow, flicker or burn out quickly in an application which they are not rated.  These bare bulbs do their best in heated rooms in lamps, or open light fixtures (such as sconce lights or ventilated globes), and where the switch just goes on and off.

Because open spiral (and open multi-tube) CFLs are easily broken and require some care if they do break, I would not put such exposed-tube CFLs in unenclosed sockets in a room where people - especially children - are active.  (Not near the Wii, for instance, over the ping-pong table, or in a crawl space.)  Lamps that protect the spiral with a secured globe or glass chimney will offer better protection, as will the enclosed spiral bulbs described in the next section.

Using spirals that come in bulbs and globes

Spiral CFLs, besides being available in bare form, also come sealed in an actual bulb.  They appear in the familiar "A-shape" that standard incandescents use, in a blunt cylindrical (bullet-shaped) enclosure, or in more decorative globes and candle-like ("torpedo") shapes.

Each style has its place.  The A-shape bulbs are useful for lamps with shades that clip to the bulb.  Cylindrical enclosures are good for utilitarian fixtures, such as bare sockets in a utility room or basement.  Globe lamps are commonly used around mirrors, but avoid using them in bathrooms where they will often be on less than fifteen minutes or where people need instant, full illumination.

Like these enclosed bulbs, CFL flood lights are also sealed spirals but have internal reflectors to minimize heat.  They are also designed to work base-up, and so are a far better choice for recessed lighting than other types of CFL.  They come in two or more physical sizes.  You probably won't like them as replacement for "spot" lights, which create sharply defined spots of light.

Use CFLs rated for particular switches & environments

We're all used to buying a bunch of incandescent bulbs and then sticking them in wherever a bulb burns out, regardless of its location or what it's doing.  This is a bad idea with CFLs.  It can lead to poor performance and shorten bulb life.  With CFLs, you'll do much better choosing a bulb for a particular shape, switch/dimmer and application.

Some of the variants discussed below are hard to find.  Some combinations just don't seem to exist, like dimmable or three-way bulbs in the candle shape.

• 3-ways:  For lamps with three-way switches, you need a compact fluorescent 3 way bulb.  Choose a CFL labeled for three-way use.  No, don't do what you sometimes did with incandescents, which was to use a one-way bulb when you didn't have a three-way.
• Dimmers:  Likewise, for dimmer circuits, CFL brightness goes down to only 10% to 40% of maximum.  When dimmed to the extreme, they may flicker and will generally not produce the romantic yellow light that incandescents do.
• Automated switches:  Avoid CFLs for electronically switched applications like dusk or motion sensors, or remote controls, unless the control specifically indicates that it works with CFLs.  Mechanical timer controls are fine.  It's mechanical if there is a little rotating manual switch to turn the light on or off, and the switch clicks when you turn it.  Many dimmers and electronic switches require current to continue flowing through the bulb throughout most of the normal alternating-current (AC) cycle.  AC current swings positive and negative, passing through zero 120 times a second.  CFLs suddenly stop carrying current below a certain voltage well above zero, so the controller switch may turn off after half a cycle - 1/2 of 1/60th of a second or less.  An interesting experiment would be to add a low-wattage incandescent bulb (an incandescent night-light, perhaps) to the CFL on the output of such a dimmer or switch and see if the control now works.  For an electronic switch, plug a multi-outlet extension cord into the control's output to create the two sockets you need.  For a dimmed array of CFL ceiling lights, screw in one incandescent or halogen bulb.  Let me know how this works for you.
• Outdoors:  Outdoor applications or unheated rooms like garages call for an outdoor rated bulb; ordinary CFLs may not even start if the temperature is low enough.  (Sometimes, there is a temperature range on the package.  Check.)  The colder the environment, the longer a CFL generally takes to reach full brightness.  Using a small, unventilated glass enclosure in a cold environment adds life-shortening stress in the form of temperature cycling (very cold when off, very warm when on); use an incandescent bulb or very low wattage CFL there.
• Small sockets:  Candle-shaped or "torpedo" CFLs can replace candelabra or other decorative bulbs that use special small sockets.
• Recessed lighting:  Get CFL flood lamps for recessed ceiling fixtures.  Check for dimmer-rated bulbs if your recessed lighting is on a dimmer.
• Base up or base down:  Finally, check to make sure the lamp has no position restrictions (base up or base down) that would disqualify it for your application.  Running a CFL base up, as in a ceiling fixture or pendant lamp, increases life-shortening heat on the electronics at its base, especially if the lamp is enclosed.  The rated lifespan of lamps designed for this sort of thing take this stress into consideration.