Lately, I've been thinking about light bulbs. Flipping through a natural products catalog I find, among the buckwheat-hull-filled yoga mats and water-filtration systems, some two-page spread on "full-spectrum" light bulbs. The catalog insists that full-spectrum lighting has "been proven to improve mood and reduce eye stress and strain." I paid a little bit of attention when super energy-efficient compact fluorescents first hit the market in the mid–'80s but never actually started using them. Is it time to change my light-bulb habits?
The lighting section of my local hardware store offers a bewildering array of bulbs: cool-white fluorescents, warm-white fluorescents, compact fluorescents, tiny halogen bulbs, halogen bulbs sized for standard Edison sockets, Miser bulbs, Longlife bulbs, full-spectrum bulbs—not to mention good old-fashioned Soft Whites.
So, how are all these bulbs different? Which one is the most efficient? Do full-spectrum bulbs really prevent cavities? How much of the packaging terminology is bogus marketing hype? Here are answers to these questions, as well as everything else you ever wanted to know about light bulbs (and some you didn't).
There are four things you need to know when you're considering a bulb:
The Main Types of Bulbs
Light bulbs—or "lamps," as they're known in the industry—work in one of two ways. Some heat a thin strip of metal until it glows—the word incandescent means "glowing or white with heat"—and this is how traditional light bulbs work. Others electrically excite a gas, which then causes a phosphorescent coating to glow (like a fluorescent bulb).
The three main types of lamps you're likely to come across are the traditional tungsten incandescent bulbs, halogens, and fluorescents.
This is the original light bulb. It works by running electricity through a thin filament made of tungsten, which glows when it gets hot. This is an inefficient type of bulb—it takes a lot of juice to get that filament hot enough to glow—and the bulb gets dimmer over time, as tungsten evaporates from the hot filament and coats the inside of the bulb with a dark haze. Eventually the filament wears out and breaks, which is what you hear rattling around inside a dead bulb. The light it produces is much yellower than sunlight, something you've noticed if you've ever tried to take color photographs by lamplight.
If you've got one of those torchiere lamps in your office, you've used a halogen bulb. Like standard bulbs, halogens are incandescent, which means they have tungsten filaments. What's different is that the filament is encased by a small quartz glass capsule, and inside this capsule are halogen compounds (hence the name) in gas form. When electric current is applied to the filament, the tungsten evaporates; but instead of coating the inside of the bulb, the tungsten is captured by the halogen compounds and redeposited on the filament.
This chemical reaction, called the "halogen cycle," not only keeps the tungsten from mucking up the inside of the bulb but also helps the filament last longer, as the tungsten is constantly replenished. Halogen lamps produce a whiter light than traditional tungsten bulbs, because they heat up to a higher temperature. Of course, this also makes them more of a fire hazard because they can more easily ignite that set of curtains nearby.
Longer bulb life, whiter light, better light quality over time—this all sounds wonderful. Naturally there's a catch: The halogen cycle only happens above a certain temperature, so you have to crank up the bulb to the top of its range for about 15 minutes once every couple of months (or whenever you see the glass casing darkening) to keep it from burning out as fast as an incandescent. If used consistently at the highest setting, a halogen bulb will last twice as long as a tungsten bulb.
Although fluorescent tube lamps are used in basements and under kitchen cabinets in some homes, the most versatile of fluorescents is the compact fluorescent. It too consists of a tube, but one that is smaller and looped over itself. Compact fluorescents are handy because they can fit in a regular screw-base Edison lamp socket.
These bulbs work by running electric current through the tube, which is filled with argon and mercury gasses. The electrified gasses produce ultraviolet radiation, which then activates a phosphorous coating on the inside of the glass that produces light. Fluorescents last for ages and are energy efficient, but generally don't render color as well as halogens or standard light bulbs. Tube fluorescents rate anywhere from 52 to 90 on the CRI, while compact fluorescents rate around 80. They can be purchased according to color temperature (cool, which is bluer; and warm, which is redder).
Labels and Marketing Gimmicks
Manufacturers of full-spectrum light bulbs—which can be incandescent or fluorescent—make elaborate claims about the health benefits of this type of light. Unlike standard bulbs, full-spectrum bulbs emit light in all parts of the visual color spectrum as well as some in the ultraviolet range. Some studies have suggested that this is why they're better for your eyes and can lift your mood, combat seasonal affective disorder, reduce fatigue, and even reduce cavities and hyperactivity in children. But a recent review of these studies by Canada's National Research Council's Institute for Research in Construction (those Canadians take artificial light very seriously) blasted most of those claims and concluded that there's no concrete evidence to support them.
The Canadian study did find that the trace amounts of UV light emitted by full-spectrum bulbs could be helpful for the production of vitamin D for people in extreme circumstances (living in submarines, homebound, etc.). And the color rendering was better, which meant that full-spectrum lights are preferable "in the case of tasks requiring fine discrimination of colour," such as "matching dental ceramics." Otherwise, what mattered most was the brightness of the light, not the width of the spectrum. In fact, there are some downsides to using full spectrums: They are less efficient than standard fluorescent bulbs and may not last as long.
Soft White does not refer to brightness or color quality, but simply to the way the light is diffused. The inside of the bulb is coated so that the light is less focused and makes shadows with less-distinct edges. Misers use less energy than regular bulbs but also may have slightly lower light output. This should be reflected in lower lumens ratings. Longlife bulbs do just what you think—they last longer. Like Misers, they may also have slightly lower light output. Bulbs that are both Misers and Longlifes can give off as much as one-third less light than standard bulbs.
So, What's the Best Deal?
This chart shows how the various bulbs affect your light bill over the course of 10,000 hours (that's one lamp, switched on for eight hours a day, for just under three and a half years). Fluorescent bulbs are the most expensive, but they also last the longest and are the most efficient. Even so, the difference isn't huge. Replacing your incandescent desk lamp with a compact fluorescent will save about $9.38 in electricity a year, and over three and a half years you save a little less than $26 after factoring in the cost of buying the bulbs. (Click
Plus, fluorescents emit strange noises and make your skin look funny. I tried switching over to compact fluorescents in my apartment, and granted, in some cases the difference wasn't noticeable. The light above my stove, for example, which has a golden filter covering it, looked just as it always did. But in the bathroom, the fluorescent light made my skin a distinctly different color. My lips looked redder, and so did the acne on my forehead. The worst change was in the living room, where three off-brand ("Lights of America") compact fluorescents flickered and buzzed. (Later I discovered that this abominable flicker was because the overhead lights' dimmer was on. When they weren't dimmed, the flicker was not visible, but the buzz never went away.) I ended up switching back all but a few in the kitchen and bathroom—I like the idea of saving a few watts and seeing the acne clearly.
Technically, tungsten incandescents—plain old light bulbs—are the next most efficient, followed closely by halogens. But halogen bulbs last longer. A clear 300-watt incandescent bulb rated to last 750 hours gives out about 6200 lumens. A tubular halogen bulb of the same wattage lasts 2,000 hours and gives out 5950 lumens. To my eye the halogen looks much better—the light was whiter and somehow more crisp.
If the look (and sound) of fluorescent lights doesn't bother you, they are the cheap, efficient choice. If you are willing to pay more for the bulbs and willing to spend a little more on electricity (and risk starting a fire), halogens are the deluxe choice. The light they provide is bright, white, and pleasant. And smack in the middle are good old-fashioned tungsten incandescents: cheap, easy, and pleasantly familiar.