How to choose

If you're buying CFLs or considering LEDs, look for rebates from retailers and utilities and at www.energystar.gov and www.dsireusa.org/incentives. And save your receipts in case there's a problem. Also keep in mind:

Think about the fixture

CFLs last longer and perform better if they're on for 15 minutes or more. That longevity makes them good for hard-to-reach fixtures. But they take time to reach full brightness, from about 30 seconds for spirals to roughly 2 minutes for recessed bulbs and 3 minutes for outdoor bulbs, so don't use them in staircases or other areas where you need instant brightness. If you don't like the swirly look of CFLs, use a covered version. But those aren't as bright, which could be a problem if your light fixture's shades are dark, frosted, or textured. Because CFLs contain a small amount of mercury, don't put them in lamps that children could tip over and cause the bulb to break. If a CFL shatters, don't panic; just follow the cleanup tips at www.ConsumerReports.org/broken_cfl.

Twelve-watt LEDs are designed for many applications, including table lamps and ceiling- and wall-mounted fixtures, much like the 60-watt incandescents and 16-watt CFLs they're replacing. LED bulbs are even cooler to the touch than CFLs.

Note the lumens

Lumens indicate how much light the bulb provides. Buying a bulb with just the right brightness and the fewest watts saves energy and money. Energy Star suggests that a 60-watt incandescent and its CFL or LED replacements have at least 800 lumens. Our tests found that some CFLs are slightly dimmer than comparable incandescent bulbs and continue to dim as they are used.

Consider the kelvins

The color of the light is measured by its temperature in kelvins (K). To match a soft-white incandescent, get a CFL or LED with 2700 K. The light from bulbs with 3000 K is comparable to the whiter light of halogen bulbs, while bulbs with 3500 K to 4100 K give off a cool, bright white light. To mimic daylight, choose bulbs with 5000 K to 6500 K.

The Color Rendering Index (CRI) ranges from 0 to 100 and indicates how accurately colors appear under the light. The higher the CRI, the better. Incandescent bulbs are near 100. Most CFLs we tested have a CRI in the low 80s. We haven't verified the CRI of LEDs yet, but manufacturers say they will be between 80 and 90.