Best lightbulbs

The incandescent lightbulb hasn't changed much since Edison's time. And though it was revolutionary in 1879, Edison's bulb is an energy hog. Less than 10 percent of the energy it uses produces light.

That inefficiency makes the incandescent long overdue for a makeover. Compact fluorescents, light-emitting diodes, and halogen bulbs each have advantages, but unlike the incandescent, there are differences in their performance and savings.

Our previous tests of CFL and LED replacements for 60-watt bulbs found many stellar choices. But when you're replacing 100-watt incandescents, our latest tests of CFLs and halogen bulbs reveal that you may sacrifice some brightness to save money.

The Energy Independence and Security Act of 2007 requires most screw-in lightbulbs to use at least 27 percent less energy by 2014. CFLs, LEDs, and some halogen bulbs, a type of incandescent, meet that requirement. Standard incandescents do not and are being phased out. As of Jan. 1, 100-watt bulbs were no longer made or imported but can be sold until supplies run out. The 75-watt incandescent bulb goes away in 2013, and a year later it's lights out for 40- and 60-watt bulbs.

CFLs save money. Fans of 100-watt incandescents like their added brightness. The halogen bulbs remained brighter than the CFLs and about as bright as a 100-watt incandescent. But when compared with a 100-watt incandescent, a CFL can save you $100 or more on electricity per bulb over its lifetime, while a halogen bulb will save only $3 to $8.

All bulbs lose brightness over time, including old-fashioned incandescents. But even the brightest CFLs were only about 1,400 lumens after 3,000 hours of testing. Energy Star recommends 1,600 lumens or more to replace a 100-watt bulb when new, though it allows lumens to drop off as CFLs age. None of the bulbs' lumen output declined more than Energy Star allows. (Lumens measure brightness; watts indicate energy use. Those numbers are on the Lighting Facts Label on the packaging.)

Brighter but not better. Brightness becomes especially important as you age—starting about in your 40s to early 60s. As the lenses in your eyes become more rigid and then cloudier, more light is needed to provide contrast, says R. Linsy Farris, M.D., a professor of clinical ophthalmology at Columbia University. Even so, brighter wasn't necessarily preferred, according to 12 staff members age 40 and older.

We asked each staff member to sit at a desk and read for a couple of minutes under two CFLs from the same brand, a new bulb and one that had undergone 3,000 hours of testing and was about 200 lumens dimmer. They read under each light separately. About half preferred the dimmer bulb. But when the bulbs were put side by side, almost all of the staff members were able to tell that the new CFL was brighter. We'll continue testing the CFLs to see whether lumen output drops more.

Halogens have advantages. In addition to brightness, halogens are dimmable and brighten instantly. Their Color Rendering Index is also higher. CRI measures how accurately the bulb displays colors. Both halogens we tested use less energy than the incandescents they replace but use significantly more than CFLs, and they don't last nearly as long. That short life span, similar to an incandescent's, is one reason halogens don't meet Energy Star standards.

LEDs lag. Prices of LEDs are dropping fast, but LED replacements for 100-watt bulbs from major manufacturers aren't available. They're working on fitting all the diodes and circuitry needed to produce enough lumens into a standard-sized bulb, and on dispersing the heat those components generate. They hope to have those LEDs in stores later this year. In the meantime, we're testing an LED that replaces a 75-watt bulb. As you switch to more efficient bulbs, we'd like to hear your questions or comments. Go to www.ConsumerReports.org/lettertoeditor.