What it means. Socket saturation represents the number of lighting fixtures that use compact fluorescent lightbulbs in this country, according to the folks who run the federal government's Energy Star program.

But the term is actually a misnomer: Although 70 percent of all U.S. homes have at least one CFL—the average is 4.4 CFLs per household—only around 11 percent of all residential sockets are fitted with a CFL, according to Energy Star's March 2009 "Big Results, Bigger Potential" market profile (PDF). Hardly a saturation point. That Energy Star report even acknowledges that "Despite recent market growth, CFL household saturation is still low throughout the United States, even in regions with successful and long-standing energy efficiency programs. . . . Overall, there is still plenty of room for the CFL market to grow." Rush Limbaugh, bombastic basher of CFLs, would probably be happy to read about this less-than-significant saturation.

Why the buzz? Given that CFLs are not an emerging technology and that they can save you significant money over their life span, you'd think that their market penetration would be deeper. Plus, all the coverage of these energy-efficient lightbulbs—including our October 2009 report, which includes ratings of two dozen different CFLs (available to subscribers)—seems like it would have been a sales booster, too.

There are a number of likely causes of this modest socket saturation, including problems with the bulbs themselves, such as cost, quality, performance, and light quality. Recession-driven belt-tightening by consumers is another reason for the shallow penetration. Indeed, even as the price of CFLs has come down, their 2009 sales have dropped 25 percent from their 2007 peak, according to the National Electrical Manufacturers Association.

The long CFL life span and fewer available in-store promotions and incentives from utilities haven't helped sales either, according to Christina Kielich, a spokeswoman for U.S. Department of Energy.

If you want to take advantage of the money CFLs can save you—about $56 over the average bulb's life—follow the buying advice from our October 2009 report and remember:

• CFLs aren't ideal for every application. They work best in light fixtures that remain on for long periods since frequent cycling on and off can shorten their life, and you won’t get the maximum energy savings from fixtures that are left on for only a few minutes at a time.
• Color is key. As with all lightbulbs, CFLs come in different   "temperatures"—that is their yellowness, blueness, or whiteness. So learn about their various colors as well as their light output (lumens). And since it might take some trial and error to find CFLs that work in your surroundings, save your receipts so you can return bulbs that don't work for you.
• CFLs take time to fully brighten. Since run-up time ranges from 27 seconds to 3 minutes for the bulbs in our tests, don't use CFLs in areas where you need instant light.
• Energy Star-qualified bulbs are best. In our tests, most non-Energy Star CFLs had lower overall scores than Energy Star models. e-mail | Twitter | Forums | Facebook

Essential reading: CFLs, including all we've tested, contain small amounts of mercury. To keep mercury from being released into the environment, don't throw CFLs out with the trash or your regular recycling. To learn how to dispose of them properly, contact your local department of public works. And if a CFL breaks, follow these clean-up instructions. Finally, if you have you avoided or stopped using CFLs at home, tell us why by leaving a comment below.