After a lifetime with incandescent bulbs around the house, compact fluorescents can be confusing.

Some tips:

Codes for colors: Light from CFLs does not look like light from other sources. The U.S. Department of Energy recognizes six color categories, indicated by a number on the base of the bulb that ends with a "K." The range is from 2,700K (the most yellow, or "warm white") to 6,500K (the most blue, or "daylight"). Preferences seem to vary by region and demographics.

Other surprises: Only certain CFLs work with dimmers, timers and in low (outdoor) temperatures, although their numbers are increasing. Meanwhile, carefully check the fine print on the packaging and the base of the bulb.

Efficiency standards: Products marked "Energy Star" have met efficiency guidelines set by the federal government.

Cost savings: A typical CFL costs much more to purchase than a typical incandescent but saves even more money over its lifetime because it uses less energy and lasts far longer. Online calculators can get very specific.

Mercury hazard: The new federal maximum of 5 mg for most bulbs (6 mg for higher wattages) takes effect in November, although the average bulb currently on the market already is in compliance, the U.S. Department of Energy says. The risk from 5 mg in a broken bulb is negligible, but it still must be cleaned carefully, the DOE says. The Environmental Protection Agency guidelines include opening all the windows in the room for 15 minutes and scraping the debris into a sealable plastic bag or jar.

Disposal: Because of the mercury hazard, CFLs should be recycled (separately from household bottles and cans). Curbside pickup is rare, but some stores and various hazardous-waste programs accept them.

The next big technology: LEDs (light-emitting diodes) are less-developed for household use than CFLs but promise even greater savings eventually.