A. An exterior security light is a bad spot for a CFL. Inside the house, the start-up time for today's CFL is just a fraction of a second. But if the gas inside the bulb is cold, as it can be outdoors or in an unfinished basement or attic, it can take a few minutes for it to warm up and the bulb to brighten. Also, CFLs provide big energy savings only if used in lights that are left on for extended periods. The frequent on-and-off switching of a motion detector shortens the bulb's life.
And despite some erroneous reports, you've got plenty of time to buy incandescents. The 2007 energy bill requires a 30 percent efficiency improvement by 2012. Today's incandescents can't do that, but GE says it's developing ones that will. It's also possible that something entirely different will become the next standard. One contender is light-emitting diode (LED) bulbs, the technology behind flat-screen TVs. In any case, the efficiency deadline is years away, so there's no need to go buying up all those old incandescent floods at the home center. Besides, something even better's bound to come along in the next few years.