Compact florescent light bulbs have garnered cries of disgust from consumers since they were introduced thirty years ago. These bulbs were too big for some lamps, expensive ($20 or more), flickered and buzzed, and had poor light quality (a cold dimness). But technology has caught up with customer demands for energy-efficient bulbs that shine warm, bright light similar to standard incandescent bulbs.

Popular Mechanics did a controlled study this year on compact florescent (CF) bulbs versus a 75-watt incandescent bulb. Researchers found the incandescent was slightly brighter than the florescent bulbs, but the latter had better overall light quality. And the test subjects couldn't tell the difference between them.

The best reason to use CF bulbs, though, is the energy efficiency. They use 75 percent less energy, produce 75 percent less heat and last up to 10 times longer than incandescent bulbs, according to ENERGY STAR (administered by the U.S. Department of Energy and Environmental Protection Agency).

"If every American home replaced just one light bulb with an ENERGY STAR qualified bulb, we would save enough energy to light more than 3 million homes for a year, more than $600 million in annual energy costs, and prevent greenhouse gases equivalent to the emissions of more than 800,000 cars," the federal program said.

CF bulbs are clearly better for the environment. But there are some things to consider before running out to purchase them.

A watt refers to how much energy the bulb consumes. You'll want a low-watt CF bulb because it's so efficient. For example, a 15-watt CF is equivalent to a 60-watt incandescent. This amounts to about $65 in electricity savings over the life of the bulb*. Just make sure the bulb has an "ENERGY STAR" label to assure quality.

It's helpful to know how CF and incandescent bulbs work. CF bulbs are lit through gas discharge, where an electrical current reacts with a gas. Atoms glow to produce ultraviolet light, which mixes with phosphor to create visible light. In an incandescent bulb, however, an electrical current heats a filament until it glows.

About 90 percent of the watts an incandescent bulb uses go to produce heat rather than light. (If you don't believe this, touch an incandescent bulb after it's been on for 30 minutes. Ouch....) Using CF bulbs can reduce your cooling bills during the summer.

You should install the bulb in a fixture that has long-term use (like the kitchen or bedroom) because the bulb burns out quicker the more it's turned on and off.

When replacing an incandescent with a CF bulb, look for a color temperature (ie. the color of light) between 2,650 and 2,850 degrees Kelvin (K), which is "warm white." (You may want a brighter, 3,000K bulb in a reading light. Daylight is more than 4,000K.)

The CF bulb's spiral glass and ballast (where current mixes with gas) are often larger than traditional bulbs. If the CF doesn't fit your lamp shade or socket, then use it elsewhere in the house.

And if you're going to put the bulb in a lamp or fixture with a dimmer, make sure the CF package says it can be dimmed. Also, don't put the bulb in an enclosed or 3-way light fixture or an outside fixture unless the packaging specifies it can be used in those devices.

Florescent bulbs (unfortunately) contain small amounts of mercury, which can be highly toxic. But think of it this way, CF bulbs have about 4 mg of mercury. The average power plant emits 10 mg of the element to produce electricity for an incandescent bulb and just 2.4 mg to power a CF bulb for an equal amount of time.

If a CF bulb breaks, open windows to air out any fumes. Then, sweep and wipe up the glass fragments (but don't use a vacuum). You should put all fragments in a sealed plastic bag. Check out earth911.org for information on where to recycle or dispose of the bulb.

Finally, make sure to check your local utility company for free or reduced price CF bulbs (which retail for about $5). California's Pacific Gas and Electric Co. is giving away 1 million free bulbs, for instance. Efficient lighting helps utility companies during the summer months when electricity demand peaks.

[The nonprofit Environmental Defense has a very good guide to energy-saving bulbs.]

But energy-efficient lighting isn't just confined to compact florescent. Light emitting diodes (LEDs), best known as the tiny bulbs in Christmas lights, are even more miserly with electricity.

LEDs last 10 times longer than CF bulbs and about 130 times longer than incandescent bulbs. They can be combined to produce light bright enough for flashlights, headlamps and track lights. Cities are now putting LED bulbs in traffic lights because they burn out so infrequently, and the electricity costs are about 80 percent less.

The biggest problem with LEDs right now is price. LED bulbs that produce light equivalent to a 60-watt incandescent cost about $75.

Also, LEDs are directional rather than diffuse unlike incandescent and CF bulbs. They are good as reading lights but poor as room lights. [Check out Eartheasy]

Compact florescent light bulbs are a much more popular choice.

CF bulbs are available in most major stores. Australia is looking to replace its incandescent bulbs with CF ones. A California legislator has even promoted banning the inefficient bulbs in the state by 2012. This would certainly be a boon for energy-saving lights like the compact florescent.

*Assuming the CF bulb lasts for 15,000 hours.