Most of us take the lights in our home for granted. Whether we spend our evenings lounging around in fuzzy slippers or plowing through to-do lists, we rarely give a thought to the bulbs burning away in this room or that. Our heavy reliance on artificial light, however, takes a toll on the environment. Though inexpensive and effective, the traditional incandescent bulbs we depend on most are wasteful: Only about 10 percent of the electricity used by each bulb is converted into light; the rest becomes (often unwanted) heat.

This inefficiency puts pressure on the environment by forcing power plants to burn more fuel than they'd otherwise have to-cranking out more greenhouse gases in the process. In fact, the average household contributes more than twice the greenhouse emissions of the average car, according to Energy Star.

Fortunately, the solution to this problem is as simple as changing a lightbulb. Compact fluorescent lamps (CFLs) are the most readily available and efficient alternative on the market. CFLs have been brightening things up since the '80s, but they've evolved. Back then, they were expensive, unreliable, and hard to fit into many typical fixtures and lamp designs. Today's bulbs are affordable, smaller, and widely available, and the light they give off is a lot more flattering and easy on the eyes than the harsh, sometimes flickery output of their predecessors. What's more, CFLs provide the same amount of light as incandescents, but they use two-thirds less energy and last eight to 10 times longer.

Bulb breakdown: how they work
The typical incandescent lightbulb houses a thin filament, usually made of the metal tungsten (this is the little piece of tightly coiled wire you can see inside an unfrosted bulb). Electricity flowing through the filament raises its temperature-to 4,000 degrees Fahrenheit, to be exact. This extreme heat causes the filament to incandesce, or glow brightly. (It also heats up the glass, of course, as we've all discovered when trying to replace a blown-out bulb too soon!)

Fluorescent bulbs work on a different principle altogether. In a CFL, for example, electricity-which is first converted to the proper voltage by a transformer, known as a ballast, in the bulb's base-flows between the electrodes located at each end of the spiral tube. The tube itself contains a mix of gases (generally argon and mercury vapor), and the electricity causes the mercury atoms give off ultraviolet light. This ultraviolet light, in turn, causes the phosphor coating inside the tube to fluoresce-that is, to radiate light. Fluorescent lighting is so efficient because only around 30 percent of the electrical energy used is wasted as heat.

Replacing an incandescent couldn't be easier, and there are no mathematical equations involved, just a bit of bulb terminology. Though we generally refer to incandescent bulbs by their wattage, a watt is merely a measure of the power they consume. Their light output, on the other hand, is measured in lumens, A 60-watt incandescent and a 13-watt CFL that both provide 800 lumens of light will be equally bright, but the CFL will use 75 percent less energy. As a general rule of thumb, the more lumens listed on the packaging, the more light output. "The amount of lumens you choose will depend on what you're using the light for, and how-if it's being used for ambiance, task lighting, whole-room illumination, etc.," says Wendy Reed, campaign director for Energy Star. If you find that your CFL doesn't give off enough light, Reed recommends purchasing the next highest CFL wattage. "You will use only a few more watts of energy to get a much brighter light," she explains.

Most CFL manufacturers list a bulb's incandescent equivalent in watts right on the package. To get the light that works best for your intended use, shop as you would for a standard bulb, choosing "warm" or "soft white" for warmer output (which is kinder to skin tones) and "cool white" or "daylight" options for situations, such as task lighting, where brighter output is desirable. If you want to see how incandescents and CFLs compare in terms of energy use and light output, check out the Light Output Equivalency chart on the Energy Star website.

A lifetime of savings: the cost benefits of CFLs
Compact fluorescent bulbs cost anywhere from $2 to $10 more than incadescents, but the benefits are dramatic. A $3 CFL will lead to lower electricity bills in about five months, and will run for 8,000 to 12,000 hours (though turning it on and off frequently will shorten its life). At that rate, if your lights are on for an average of four hours a day, your CFL can last up to eight years. An incandescent, by comparison, usually lasts between 750 and 1,000 hours.

According to Energy Star, every U.S. family would save about $60 in energy costs each year by replacing the incandescent bulbs in five of its most frequently used fixtures with energy-efficient alternatives. If every American home changed just one bulb, we'd save more than $600 million in annual energy costs, and prevent greenhouse gases equivalent to the emissions from more than 800,000 cars.

All CFLs conserve energy and cash. But to maximize your savings, keep an eye out for the Energy Star label. Energy Star-qualified CFLs must meet performance criteria devised by the U.S. Department of Energy and the U.S. Environmental Protection Agency. To earn this label, manufacturers must submit data to the DOE and EPA demonstrating that a particular bulb lives up to performance specifications covering quality, lifespan, and efficiency. For example, says Reed, the bulb "must turn on within one second, reach full brightness within three minutes, fall within a specified color range (or be otherwise labeled on the packaging), and last a minimum average lifetime of 6,000 hours." It's estimated that 80 to 90 percent of all CFLs on the market have earned the Energy Star label. In addition, all Energy Star-marked CFLs must come with a two-year warranty for residential applications.

size
CFLs are designed to fit into standard lightbulb sockets, but there isn't a standard size for the attached glass globe, if there is one, or for the ballast. "CFLs have become highly compact," says Reed. "However, the higher the wattage, the larger the globe and the ballast supporting it." As a result, the glass globe (or even the uncovered coil itself) may be so large that it extends beyond the fixture, which can be especially problematic if the light has a cover. In addition, there are no CFL alternatives for the smaller sockets typically found in small decorative and desk lamps.

Weather
Temperature can have an affect on a CFL's performance. Some CFLs can be used outside in temperatures ranging from -10 to 120 degrees Fahrenheit. However, in extremely cold temperatures the bulb may take longer to reach its full brightness. Be sure to consider the location of your fixture, and if necessary, choose a bulb specifically designed to provide steady light regardless of temperature. Energy Star has rated several weatherproof CFLs, which are designed for outdoor lighting and can be exposed to rain.

Style options
Although CFL technology is still evolving, the bulbs are currently sold in a variety of shapes besides those intended as standard incandescent replacements, each offering a different kind of light distribution. The following should be readily available at your local home-appliance or lighting store.

Dimmable and 3-way bulbs These typically carry a higher price tag than standard spirals, but they'll eventually save more than double their initial cost on your energy bill. Standard CFLs are not recommended for use with dimmers, because this can shorten the life of the bulb and, in some cases, will void the warranty.

Decorative Candle, torpedo, and bullet shapes are designed to replace similar incandescent models. These decorative shapes can be used in some chandeliers, wall sconces, and porch lights. (Although CFLs for chandeliers are becoming more easily available, they aren't yet sold widely, and they aren't currently rated by Energy Star.)

Globe lamps These round CFLs can be used for bathroom vanities, clamp lamps, ceiling-mounted fixtures, and some exposed outdoor fixtures.

Reflectorized bulbs Reflector CFLs are intended for non-dimmable recessed and track lighting and some outdoor spotlights. Keep in mind that it's not a good idea to use CFLs in completely enclosed recessed fixtures, such as covered ceiling can lights. These fixtures retain too much heat to safely permit the use of CFLs.

Bug lights These bulbs have a special coating on the glass that repels indoor and outdoor pests.

Shattered hopes: a note about proper disposal
CFLs contain a small amount of mercury, and should therefore be disposed of in the same way as any other hazardous household item, such as paint or batteries. Don't toss CFLs in the garbage. Instead, check out Earth 911 and browse through disposal options by ZIP code, or call your local recycling agency for guidelines. Furniture giant Ikea is spearheading a take-back program for used CFLs, and other retailers are exploring the possibility (you can find more information at Lamp Recycle). If you discover that your community doesn't offer hazardous-waste disposal, Energy Star advises you to place the bulb in two sealed plastic bags before chucking into the garbage. However, if your waste-management agency incinerates its garbage, then you need to search a wider geographic area for proper disposal. Mercury is a toxic pollutant that gets released into the air when incinerated.

Research has shown that, since there's such a small amount of mercury in each bulb, you won't face any immediate health risks should the bulb break. Here's what you need to know to protect yourself:

1. Wearing disposable rubber gloves, sweep-don't vacuum-the broken pieces and particles onto cardboard or stiff paper.
2. Place all fragments in a sealed plastic bag, then put that bag inside another. Clean the area with a damp paper towel or wet wipe. Use sticky tape to remove any hard-to-see shards or powder.
3. Ventilate the room by opening a window, and restrict access to the area for at least 15 minutes.
4. Wash your hands after disposal. The next time you vacuum the area, remove the bag or wipe the empty canister and dispose of any cleaning materials using the steps described above.

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