Compact Fluorescent (CFL) was designed to replace incandescent and halogen lamps as an energy-efficient alternative. CFLs feature either a twisted glass bulb style or a bent, small tube. The base of a CFL is either a screw-in or a plug-in style.Compact Fluorescents are low power consumers, like fluorescent tubes, and sized to fit the same E26 socket as an A19 bulb. Some also contain an integrated ballast, like LEDs.Although you can choose from a variety of color temperatures, CFLs color shift over time (unlike LEDs that produce same color temperature throughout the life of the bulb). CFLs include a warm-up period like fluorescent tubes of about 10-30 seconds.While CFLs are a lower power consumer than those traditional bulbs mentioned above, LEDs are lower still in their power consumption.