Light bulb basics

Light bulb basics

Even a compact fluorescent light bulb that burns out prematurely uses less electricity while you use it -- but you may or may not break even. The environmental advantage of a compact fluorescent bulb also depends on its lifetime, since incandescent light bulbs take fewer resources and electricity to manufacture. We found loads of statistics estimating the environmental savings of switching to compact fluorescent light bulbs, but again -- it depends on your situation and your care in selecting and using the bulbs.

If your electrical utility burns coal, then switching from incandescent light bulbs will have more environmental benefit than if you use hydroelectric power. Summer savings are higher than winter in most areas, because compact fluorescent light bulbs burn much cooler, saving air conditioning. If most of your incandescent light bulbs are on dimmers kept low most of the time, your savings will be much less (and you may have trouble finding a compact fluorescent light bulb that will work for you).

It's easier to estimate your personal dollar savings than to calculate the environmental benefits of switching from incandescent to compact fluorescent light bulbs. EPA regulations will drastically lower the mercury emitted by coal-burning utilities in the U.S. in coming years. Since nearly all light bulbs are manufactured in China (and a few in India and Thailand), it's hard to predict the environmental effects on those countries and on worldwide air quality. Safe light-bulb disposal and recycling is also unpredictable at this point.

You'll probably save some money by switching to good-quality compact fluorescent light bulbs, as long as you use them in the right fixtures, keep them on for at least 15 minutes at a time and exchange any defective bulbs without paying return shipping. So it's reasonable to switch from incandescent light bulbs now, before their mandated phase-out in 2012. But you'll probably be happier with your purchase if you choose carefully and also lower your expectations. For use with dimmer switches, new energy-saving halogen light fixtures are a better bet.

Experts agree that LED light bulbs will be superior to compact fluorescent light bulbs in many ways -- eventually. For now, they're worth considering for certain purposes, but are too expensive and dim for most settings. Prices are projected to fall steadily, and new LED technology promises to increase light output dramatically. (See "The Buzz" below for details.)

Each light bulb type has advantages and disadvantages, so most households will find a mix of light bulbs best. This report covers only light bulbs that screw into an Edison medium base. That's the most typical socket most incandescent bulbs now fit.

Medium-base light bulb types

Compact fluorescent light bulbs -- Technically called "compact fluorescent lamps" or "CFLs" -- these save energy, and are also long-lasting when kept on at least 15 minutes at a time. Only a few models are usable with dimmers, three-way lamps or recessed lighting, or in damp settings. Some are designed just for "base-down" or "base-up" fixtures. Drawbacks include the fact that these bulbs contain mercury, cadmium and other toxic materials. In addition, CFLs can take about half a minute to warm up to full brightness. User reports indicate that there might be a relatively high percentage of defective bulbs, or that CFLs simply might not typically last as long as expected. Another issue is that CFLs gradually lose 20 to 30 percent of their brightness over time, and they can interfere with sensitive electronic devices. Finally, CFLs require careful disposal (and cleanup if broken) to avoid contaminating soil and water with mercury.

LED light bulbs -- These solid-state light bulbs are even cooler and more energy-efficient than CFLs, and they contain no mercury or lead. Experts say these are particularly good for light fixtures that require instant illumination (such as stairways or garage doors), where bulbs are difficult to change or where a focused task light makes the most of directional light. The biggest drawback right now is cost. In addition, LED light bulbs are relatively dim -- and they get even dimmer during their lifetime -- and they don't show colors well. There's not enough feedback as of yet to draw any firm conclusion about reliability or longevity.

Halogen light bulbs -- These light bulbs also turn on instantly. Unlike CFLs, they can be used with standard dimmer switches, contain no mercury and are unaffected by frequent on-off cycling. New energy-saving halogen light bulbs use about 30 percent less electricity than incandescent bulbs and last an average of two years. A few fit medium-base screw-in light fixtures. Halogen bulbs are good for both general and focused lighting. However, these save less energy than compact fluorescent and LED light bulbs. The light they give off is slightly cooler than most incandescent or soft white light bulbs. Currently the only full-spectrum halogen light bulbs require an adapter for use in medium-base screw-in track lights and they don't fit other medium-base fixtures.

Incandescent light bulbs -- These are the "regular" light bulbs that are the least efficient, producing more heat than light. They cost the least initially, but cost the most in the long run (taking electricity into account). For environmental reasons, legislation is phasing out most incandescent light bulbs by 2012 (and in some countries much earlier).

Except for halogen light bulbs, whose light is usually white, each type of light bulb is available in various color temperatures, usually specified in degrees Kelvin (K). Most light bulbs range from a warm 2700K through various steps of "cooler, bluer" to a very bluish-white 5000K often called "full spectrum." Light bulbs that emit a lot of blue (not always visibly) are controversial for health reasons; see below for more on this.

Many owners express disappointment in the light bulbs they bought, especially in compact fluorescent light bulbs expected to last a long time. This is partly due to quality control problems in the industry as just about all light bulbs are made overseas with cheap labor. But it also may be due in part to misunderstandings about usage -- for example, most light bulbs should be handled only by the base, or with gloves to prevent oil from fingers shortening their life. It's also easy to misunderstand how light bulbs are rated and described.

"Lifetime in hours" means the median number of hours that samples of the light bulb model have been tested to last. That means that half the light bulbs will last longer, but half will last a shorter time. So it doesn't mean you can expect every light bulb of that model to last at least that long; half of them won't. Light-bulb lifetime ratings are also calculated under ideal conditions of temperature, humidity and on-off cycling -- which is unlikely to match your situation. (For example, if a compact fluorescent light bulb is turned on for only five minutes at a time, its estimated lifetime is reduced to that of an incandescent light bulb.)

"Lumens" is a measure of light output, but both the effective and perceived light output can vary in several ways. Lumens are measured for fluorescent light as the average light output at 40 percent of the rated lamp life, since most of their decline in brightness occurs earlier. Also, light bulbs that put out the same lumens may seem dimmer or brighter depending on the fixture. A light bulb used in a focused task lamp, for example, may not need as many lumens as a light bulb used in a floor lamp that radiates light all around. The color temperature of the light bulb can also affect how bright its output appears to be, with the effect varying somewhat depending on the type of light bulb. Also, the human eye perceives less difference in brightness than the objective increase in lumens measured by lab instruments, so it takes a bigger increase to be noticeable to the human eye.

"Warranty" is usually specified in hours or years, but retailers and manufacturers vary a great deal in how they handle warranty claims. As many owner-written reviews testify, a light-bulb warranty doesn't help much if the company requires you to pay shipping to return defective bulbs. Retailers may or may not accept returns. Also, many light bulbs are designed for specific kinds of light fixtures, and using them with a dimmer switch, enclosed or recessed fixture, or in a damp setting -- even with the same medium-base screw-in socket -- may void the warranty.

"Starting time" isn't the same as "run up time." Compact fluorescent light bulbs must start within one second to earn ENERGY STAR certification, but may still take up to 30 seconds or so to attain full brightness. LED, halogen and incandescent light bulbs start so fast that the delay is imperceptible, and need no "run up time" at all. When first getting used to compact fluorescent light bulbs, the delays can be disconcerting. Reviews warn that in a few situations the delays can be dangerous -- for example, if you depend on instant light for safety on stairs.

Most dimmer switches are designed for use with incandescent light bulbs. Reviews warn that even when labeled "usable with dimmers," it's possible that a compact fluorescent light bulb won't work with your dimmer switch. The same is true of 3-way light fixtures: a 3-way compact fluorescent light bulb may or may not work. Your best bet is to replace incandescent light bulbs first in ordinary light fixtures with plenty of airflow that stay on for hours at a time. Both heat and cycling on and off often can drastically shorten the lifetime of compact fluorescent light bulbs.

Incandescent light bulbs

Since medium-base incandescent light bulbs are being phased out, we found few reviews comparing them. The few incandescent bulbs that do get recommendations in reviews are "full-spectrum" light bulbs: GE Reveal (*est. $5 for four) and Sylvania Daylight (*est. $4 for four-pack) cost quite a bit less than Verilux (*est. $8). However, all three get good marks compared with ordinary 2700K incandescent light bulbs.

Owners note that these "full spectrum" light bulbs seem a little dimmer than regular incandescent light bulbs of the same wattage, but find the light pleasing. Chromalux makes a similar "full spectrum" incandescent light bulb (*est. $6), but we found no reviews of it. All four brands make 3-way light bulbs and, like other incandescent bulbs, can be used with dimmers.

Incandescent light bulbs are labeled "full spectrum" when they're coated with Neodymium, which filters out much of the yellow part of the spectrum so the light looks whiter, more like daylight. Experts point out that although their light looks pleasant, it's not truly full spectrum. If you compare a spectrum analysis of these special incandescent light bulbs with the spectrum analysis of natural sunlight, they're quite different. In a pinch they can be used to judge color for crafts, artwork and photography, but reviews say SoLux halogen lights are much better. (See the Buzz and Alternative Considerations sections below.)

 ... Continued (Compact fluorescent light bulbs)