The oldest and largest category of light source, the incandescent creates light by heating a filament with electricity until it becomes so hot it shines. Incandescent lights waste a lot of energy as most of the electricity used to create illumination escapes in the form of heat. Over the years, numerous innovations have emerged to make incandescent lighting more efficient and to use less power, overall.
The familiar “Edison-base” bulb is still the most common light source in most residential applications. It’s cheap, effective, and produces plenty of high-quality light. Used for general purpose lighting—such as table lamps, chandeliers, and flush-mounted ceiling fixtures, the bulb is designed to distribute light in all directions for general illumination.
Halogen lighting is a form of an incandescent light source that can produce a lot more light using the same amount of power. This is because the bulb is filled with a halogen gas that keeps the tungsten filament from burning down. As a result, it can be operated at very high temperatures for extended periods of time. On the downside, the intense heat can pose a greater risk of fire if care isn’t taken to keep objects away from the source.
For applications that require light to be cast in a specific direction—like downlighting “ceiling cans,” or task lighting, reflectorized light sources are great options. Parabolic reflectorized sources (PAR) are halogen bulbs designed to direct a great deal of light over a wide area. Their smaller counterparts, the multifaceted reflectors (MR), are low-voltage light sources ideal for track lighting and task lighting.
When fluorescent lighting first emerged in the 1960s as an energy-efficient alternative to incandescent, it quickly developed a bad reputation. These light sources could produce a sickly blue-green hue and an audible, headache-inducing hum. Times have changed, though. Today’s fluorescent bulbs still don’t create the broad-range light quality of the best incandescent bulbs, but the color temperature is much better and, thanks to improvements in the ballast technology powering them, the hum is gone. Plus, they’re still far more efficient than most incandescent light sources.
Fluorescent tube lighting like the T8, T5, and T12 are solid choices for general purpose illumination or recessed lighting in spaces where energy efficiency is a more important consideration than light quality. The tube widths are measured in eighths of an inch, so a T5 has a diameter of 5/8 of an inch, a T12 is 1:½ inches, etc.
One of the most important innovations in residential lighting has been the emergence of the self-ballasted compact fluorescent lamp, or CFL. These light sources are designed to replace traditional incandescent bulbs, and provide the same amount of light with a small fraction of the energy. Not only that, they can outlast many traditional incandescents by several years. On the downside, they don’t output the same light quality or “color-rendering” as incandescents, and if they’re installed upside-down (as in a porch light), the rising heat can shorten the life of the ballast and, consequently, the lamp life overall.
It’s important to note that CFLs, or any fluorescents, are not typically dimmable. “Dimmable” CFLs are available, although they’re a bit more expensive—and you have to make sure your dimmer switch is rated for use with CFLs, as well.
The little red and green lights on your electronic components have come a long way. Today, light-emitting diode (LED) lights are a cost-effective alternative to both incandescent and fluorescent light sources. Although still more expensive than both, LED light sources offer excellent color rendering, unbeatable efficiency, and a lamp life that stretches for decades. They’re dimmable (with the appropriate dimmer switch), and they come in just about any form factor: bulb, tube, reflectorized (PAR and MR), strip, and puck. As the technology advances, the cost is expected to drop further still, which means LEDs will likely be the most common light source around in just a few more years.
Mike Llewellyn is a freelance writer who covers design, technology, and media. He is also the founder of Sycamore Creative, a communications and design firm in Philadelphia (sycamorecreative.net). Mike’s work has appeared in Philadelphia Magazine, Architectural Record, The New York Times, and on TED.com.