incandescent v. fluorescent lights

In an incandescent bulb, electric current passing through a thin filament heats it up and causes it to emit light. To prevent oxidation, the filament is sealed within a glass bulb that is either evacuated or filled with an inert gas.

A fluorescent lamp is a phosphor-coated glass tube filled with mercury vapor. A current causes the vapor to emit ultraviolet light, which is absorbed by the phosphor coating and reradiated as visible light.

• At least 95% of the energy consumed by incandescent light bulbs is given off as heat; typically, only 2 to 3% is converted to visible light. Fluorescent lamps are 4 to 6 times as efficient. To promote the use of more energy-efficient technologies, many countries will be phasing out the sale of incandescent lights over the next several years. Incandescents can contribute to heating in the winter, and fluorescents can reduce cooling costs in the summer.
• In normal use, fluorescent lamps last up to 10 times as long as equivalent incandescent lamps. With frequent switching, fluorescents deteriorate rapidly.
• Fluorescents are more complicated, and therefore more expensive. They require a current-limiting ballast, without which they would draw too much power and destroy themselves. Larger tubes also need a starter to strike an arc in the mercury.
• Traditionally, fluorescent lamps were primarily used in commercial settings, but the rising availability of compact fluorescents has made them more common in the home.
• Fluorescent lamps are commonly larger than incandescents, and incandescents can be made smaller than fluorescents.
• Bright, small incandescents can create glare; large, diffuse fluorescents don’t.
• Fluorescents tubes can be straight, u-shaped, ring-shaped, or tightly coiled; most incandescents are variations on bulbous or teardrop shapes.
• The color spectrum of fluorescent light can be less pleasant than that of incandescent light, and it may be harder to perceive colors correctly under fluorescent light.
• Incandescents can run from alternating or direct current. Fluorescents almost always run on AC.
• Incandescents turn on instantly; fluorescents may take a moment to start.
• Fluorescent light fixtures can’t be controlled with a standard dimmer switch.
• Some fluorescents lamps may flicker noticeably, produce an audible hum, or generate radio frequency interference.
• Mercury vapor from broken fluorescent bulbs may present a health hazard.
• Fluorescents are dimmer in cold weather.

U.S. Department of Energy on incandescent v. fluorescent lights