CFLs

Compact fluorescent lamps (CFLs) are a family of small, energy-efficient lamps designed to replace incandescent bulbs. CFLs use a compact fluorescent tube or intertwined tubes containing a small amount of mercury vapor. An internal electronic ballast (or an external ballast in older designs) provides starting voltage and current regulation. When energized, the mercury vapor emits ultraviolet light, which excites the phosphor coating on the inside of the tube to emit visible light.

CFLs typically offer higher luminous efficacy than incandescent lamps, commonly around 40–70 lumens per watt, and a longer rated life, often about 8,000–12,000 hours. They produce less heat than incandescent bulbs and can be used to reduce energy consumption in residential and commercial lighting. CFLs are available in various shapes, including spiral, compact plug-in tubes, and U-shaped configurations. They come in color temperatures ranging from warm to cool and with color rendering indices around 80–90, depending on the phosphor formulation. Some CFLs are dimmable, but many are not and require compatible dimmers.

Key considerations include longer warm-up times to reach full brightness, reduced performance in very cold environments, and the presence of a small amount of mercury. Because of mercury content, CFLs require proper disposal and recycling. Environmental and regulatory shifts have increased the adoption of LED lighting, but CFLs remain in use in many regions and applications where retrofit cost or fixture compatibility makes LEDs less feasible.