With a government edict providing the push, household light bulbs as we’ve known them are rapidly becoming historical curiosities. Their replacements not only use less energy and last longer but also let us manipulate light in an entirely different way.

For starters, think lumens, not just watts. Wattage is a measure of how much electricity a bulb uses, and that’s what got conventional incandescents into trouble in the first place. They used too much electricity for too little light—roughly 90 percent of the power they consumed went into heat, not light.

Lumens is the amount of visible light a bulb produces, and that, rather than wattage, is the new metric for specifying brightness. An old-style 100-watt incandescent, for example, produces about 1600 lumens—and that’s what to look for on packaging when you buy a replacement.

What’s forcing widespread changes in lighting is the Energy Independence and Security Act of 2007. Although it didn’t ban conventional incandescents, it did toughen energy efficiency standards. Some types of old bulbs are exempt from the new requirements, but the law leaves three alternate technologies for most residential lighting: halogen incandescents, compact fluorescent lamps (CFLs), and light-emitting diodes (LEDs). All three of them are more efficient than old-style bulbs while lasting up to 50 times longer.

Less Power, More Light

All three new alternatives are more efficient, or, in industry talk, have a higher efficacy than conventional incandescents. According to DOE figures, for example, to get the same amount of light as a conventional 60-watt incandescent (about 800 lumens), you can use a 43-watt halogen incandescent, a 15-watt CFL, or a 12-watt LED. Annual energy costs for that bulb—based on two hours of use per day and energy costs of 11 cents per kilowatt hour—drop accordingly, from $4.80 for the standard incandescent to $3.50, $1.20, and $1, respectively.

There are two other factors that go into choosing a light source: color temperature and color rendering. Conventional incandescents cast a relatively warm light, roughly 2700 degrees Kelvin. Higher color temperatures mean cooler, whiter light.

If you want colors to appear exactly as they would under an incandescent light source, look for a color rendering index of 100.

Halogens, CFLs Most Affordable

Of the three technologies, CFLs and halogen incandescents have the lowest up-front costs.

Halogen incandescents are the most familiar of the three with the same shape of old-style bulbs. In the industry, that’s called an A19 bulb, where “A” is the rounded shape and “19” is the diameter in one-eighth inch units. They’re relatively inexpensive, are not affected by on-off cycling, are compatible with all models of dimmers, and come on instantly. They cast a slightly whiter light than standard incandescents, with a color temperature of 2900K-3000K.

But halogen incandescents don’t last that long (1,000 to 3,000 hours), roughly one to three years if used three hours per day. They’re also the least efficient and produce more heat than the others. In the end, you’ll get lower performance in return for greater familiarity.

CFLs are a big step up in efficiency. They use about 75 percent less energy to produce the same amount of light as a standard incandescent, and they last up to 10,000 hours (about nine years at three hours per day). Most CFLs designed to screw into standard sockets, what’s called a “medium base,” are made with a tube of glass formed into a spiral or folds. Some have coverings giving them the look of a conventional bulb.

CFLs save a lot of energy but also have some annoying shortcomings. Many of them take time to warm up, and many are not dimmable. They contain small amounts of mercury so they should be recycled. They also don’t perform well in cold temperatures, have shortened life spans with frequent on-off cycling, and will fail if subjected to too much vibration, just like an incandescent.

LEDs: The Future of Light

LEDs are solid-state devices that have become increasingly versatile and useful as residential lighting sources. With color temperatures to match incandescent bulbs, they’re also manufactured in a number of shapes and sizes to fit different types of light fixtures. They are slightly more energy efficient than CFLs, but they last much longer—15,000 hours and up.

Unlike CFLs, they’re not affected by frequent on-off cycling or by vibration, and their performance doesn’t suffer in cold temperatures (in fact, an LED produces 10 percent more light at 35 degrees than at 70 degrees). LEDs produce relatively little heat and no UV radiation.

They also contain no mercury, reducing disposal costs. Although they can be recycled, LEDs that comply with the European Restriction of Hazardous Substances (RoHS) directive don’t have to be.

LEDs, however, are not compatible with all dimmers, and light output can suffer when the bulbs don’t get enough ventilation.

The biggest obstacle to wider use, however, has been cost. Prices have fallen and should continue to go down, and utility rebates can soften the blow, depending on where you live. But good quality LEDs aren’t cheap. “They will never be two bucks,” says Cheryl Ford, Osram Sylvania’s marketing manager. “How far it’s going to drop I don’t know. But it’s not likely they will ever be as cheap as CFLs.”

Working With Digitized Light

In addition to very high energy efficiency and incredibly long service lives, LEDs can be controlled in ways that incandescent bulbs and CFLs can’t.

“LEDs are going to be the future,” says Brian Vedder, LED portfolio manager at Philips. “That’s going to be what people put into their houses.

“The initial race in LED was to have a viable product to replace existing incandescents, so there was a race to get to a 40-watt, and then the real race was to replace a 60-watt A-shaped lamp,” Vedder adds. “And similarly, on the reflector side, it was how quickly we can replace a 60-watt PAR-38 or a 90-watt PAR-38,” he says, referencing the parabolic aluminized reflector lamps common for spot and flood fixtures.

“We have now reached those levels and what we’re doing is two things: increasing the performance so we maintain the light level while driving out wattage.”