Flashback: The old Thomas Edison-like stalwart for more than a century, is inefficient. Starting in 2012, this bulb will change or be phased out. (Photo by Robert Durell)

Ninety percent of the electricity that goes into it is given off as waste heat. "Tell me another product where you're only getting 10 percent of the energy coming in converted to useful work," he said.

For those who can't quite kick the habit of energy-guzzling incandescents, halogens may be your first baby step toward efficiency.

Adding the gas reverses the deterioration of the tungsten lighting filament, making the bulb about 25 percent more efficient. Otherwise, these bulbs look and act like incandescent twins.

The next step in efficiency is CFLs, compact fluorescent lightbulbs. These have had a tough go since their introduction a few decades ago, when they were big and clunky, with poor light that didn't even come on right away. And they were expensive to boot.

Now they are cheaper, brighter, and truer, the shades of light ranging from warm white to cool. New versions are dimmable.

Most still take a few minutes to reach full brightness, but General Electric has announced a halogen "hybrid" that is instantly bright. It's due on shelves this spring.

One persistent problem, at least in terms of public acceptance, has been the mercury in CFLs, although the amounts have lessened significantly. People read the Environmental Protection Agency's instructions for cleaning up a broken bulb -- air the room for 15 minutes, don't vacuum the pieces -- and they freak.

All fluorescent bulbs, not just CFLs, have mercury. It's what Michael Myer, a lighting engineer with the U.S. Department of Energy's Pacific Northwest National Laboratory, calls "a necessary evil."

But we can't ignore the mercury that is produced in a coal-fired power plant, which accounts for roughly 50 percent of the nation's power. Scientists have compared the mercury emission that incandescent bulbs would be "responsible" for to the mercury in CFLs, and declared the CFL the better choice.

Many big-box home stores offer recycling, so the mercury is handled properly.

Engineers and first-adopters are excited now about LEDs, which hold the promise of huge efficiencies.

For now, the technology is deemed to be in the toddler stage. Or the equivalent of cell phones in about 1990, when they were like bricks you held to your ear.

So they're heavy, the light's dim, and some are infused with the color blue.

But in recent months, bulb giants Philips Lighting North America and Osram Sylvania have released 60-watt equivalents with a warm hue and in the traditional shape of an incandescent. (The external ribs on many LEDs carry heat away from the bulb.)

Myer credits the Department of Energy's "L Prize," which will be awarded to the first LED that has the same light output as a 60-watt incandescent and meets other standards. So far, Philips is the only entrant.

Sylvania's LED retrofit market manager, Ellen Sizemore, said the company was more interested in "providing the market with the best, most cost-efficient products for the masses" rather than some of the finer points of the L Prize.

So far, the price is an eye-opener -- about $40 per bulb. But Peter Soares, Philips' consumer marketing director, said the bulb would save $142 over its life for someone paying 11 cents a kilowatt-hour.

We may yet see all kinds of new technologies, experts say.

One of many newcomers is the "electron stimulated luminescence" bulb sold only online and developed by the New York company Vu1.

Certified by Underwriters Laboratories in October, it uses the technology of old TVs. A cathode generates electrons and sprays them onto the bulb's interior phosphor coating. The equivalent of a 65-watt incandescent, it costs under $20 and uses just 19.5 watts.