Burning questions about switching to compact fluorescent light bulbs (CFLs) or other energy-efficient light bulbs? Allow us to shed some light.

Q. How can a little light bulb make a difference?

A. “CFLs prevent the emission of substantial quantities of greenhouse gases and other pollutants,” says Vicki Fulbright-Calwell, lighting and mercury consultant at Ecos Consulting in Durango, Colo., and a prominent expert on the subject of CFLs. “They reduce consumer energy bills and last far longer than incandescent bulbs.”

If you replace the five standard light bulbs you use the most with CFLs, you can save roughly $60 a year on electricity. 

If every American home replaced just one incandescent light bulb with a compact fluorescent bulb, we would eliminate 1 million cars' worth of greenhouse gas emissions. That's one bulb. Most homes have 15-30 bulbs.

How many CFLs does it take to make a dent in my energy usage?

Begin by changing the bulbs that burn for more than an hour a day. Kitchens and dining rooms, family and living rooms, bedrooms, hallways, and outdoor lights — such as the porch light — are good places to use CFLs.

Another tip — it’s okay to keep those cheap incandescents around, too, if they’re in fixtures that don’t get used a lot. No need to ever change that closet light or hall light that is only on for a few minutes a week.

CFLs have strange wattage ratings. How do I know which one to buy?

You’ll need to know the wattage of the bulb you’re replacing and its equivalent in a CFL.

Are some CFLs more efficient or longer lasting than others?

There’s not much difference in efficiency between brands of CFLs, says Bill Giebler, who's sized up a whole lot of CFLs in his 10 years heading up green product sourcing at Gaiam Real Goods. But there can be a big difference in how long a CFL will last, regardless of who makes it. Some CFLs have a 10,000 hour life while others are rated at only 6,000 hours.

What about that anemic blue light CFLs give off?

“When it comes to light quality, look at the Kelvin ‘temperature,’ which is a color rating,” says Giebler. If you find the light disconcerting, you’re likely the proud owner of a ‘natural spectrum’ lamp with a Kelvin rating of 5000+ that produces a white-toward-blue light, Giebler adds.

Technically speaking, natural spectrum light is better light: It mimics light at noon on a cloudy day, reduces glare and renders better color. These are the best bulbs for reading lamps, desk lamps, and work and art stations. But they’re blue and cold and have the tendency to dig up flashbacks of your worst elementary school memories.

If you experience these symptoms, immediately find yourself a 2700K CFL bulb (often sold as “soft white” or "warm glow") that gives off a yellow light similar to incandescent light. Screw in your kinder, gentler new bulb and breathe deeply.

Can I use a CFL with a dimmer switch or 3-way switch?

Yes. CFLs made specifically for dimmer and 3-way switches are readily available now; look for them alongside regular CFLs.

Note that it’s a fire hazard to use a standard CFL in a dimming circuit. (Who knew?) If a CFL is not clearly marked for dimming, do NOT use it in a dimming circuit, even at full brightness. The same applies for a 3-way bulb — if it doesn’t say it’s for 3-way, don’t use it in a 3-way fixture.

Don’t CFLs contain mercury?

While CFLs do contain minuscule amounts of mercury, they are an environmentally friendlier choice right now despite their mercury content, because of the energy savings and reduction in coal-fired power plant emissions that result from using them. Learn more here.

Can I get a break on my power bill for using CFLs?

There are a number of utilities that offer rebates, says Calwell. She adds that since utilities will not be promoting CFLs forever, don’t count on rebates as your reason to switch. For the latest information, check with your local utility.

Are LEDs better than CFLs?

LEDs, or light-emitting diodes, use a third of the wattage of even the smallest CFL. LEDs also last even longer than CFLs (up to 10 times longer) and contain no mercury. Like CFLs, they also run much cooler than incandescents. LEDs are common in electronics and in gadgets such as headlamps made for camping.

But there's a reason CFLs are now ubiquitous while LEDs for lighting your home remain a lesser-known option: "Nothing beats a CFL for lumens per watt," says Giebler. "It’s the best for getting energy efficiency while also fully lighting a space."

Using LEDs in household lighting fixtures is still a novel concept — but Giebler says LEDs are the best type of bulb out there for reading lamps, task lighting and small areas. He says a 3-watt LED makes a perfect porch light. The light is bright enough to mark your house, yet the low output reduces light pollution. And LEDs run fine in very cold temperatures, unlike CFLs.