Most people have accepted that it's all but over for old incandescent bulbs. But CFLs—compact fluorescent bulbs, the titular replacements for incandescents—may be rapidly becoming extinct as well.

LEDs or light-emitting diode bulbs are the next lighting generation, and they've made significant advances in the last couple of years. I've been testing dozens of bulbs from companies such as Cree, GE, Lighting Sciences, Sylvania, and Toshiba, and found that not only are LEDs a better alternative with superior lighting characteristics, they offer more features than any previous lighting technology—as long as you understand how they are rated and what to look for.

LEDs offer several advantages. First and foremost is the fact that LEDs are more efficient, saving electricity—and money. A typical 60-watt replacement LED actually uses just 11 watts to produce the same brightness. They can also replace everything from reading lamps to overheads, although LEDs vent heat from the base of the bulb and so are not appropriate for completely enclosed fixtures.

Compared to CFLs, LEDs do not contain hazardous, mercury-tinged gas, and they can withstand being turned on and off repeatedly without reducing their life span. LEDs also come on instantly, unlike CFLs that typically have to warm up (which is why some people just leave them on all the time). Most LEDs are also dimmable (an expensive feature for special CFLs), and they do not suddenly burn out without warning (LEDs gradually lose their brightness before failing).

The solid-state components of LEDs can also make them potentially shock resistant and virtually unbreakable, depending on the kind of glass used. I accidentally dropped a couple of Sylvania's Ultra bulbs from a height of about five feet onto a living room carpet. No broken glass, no poison gas, and the Sylvania bulbs still worked perfectly.

The biggest downside to LEDs has been their price. Just a couple of years ago, 60-watt equivalent LEDs were $40 each or more. Today, however, the price of such A19 (standard household lamp bulb sizes) bulbs has dropped to under $10 each. That may still sound like a lot of money, but these bulbs have a usable life span equal to about 30 to 50 incandescent bulbs or 3 to 5 CFLs. In other words, based on 3 hours a day of use, an LED bulb may last you for over 20 years.

So why are some LEDs so expensive and why do some emit harsher light than others?

To understand what you're buying and the kind of light you'll get, you need to know a little about LED specifications.

Rather than looking at wattage ratings or replacement equivalence ratings, you should look at the lumen's rating of a bulb to see how bright it will be. An 800 lumens rating, for example, is about typical for replacing a 60-watt incandescent bulb.

Color temperature indicates what kind of light the bulb will emit. A “soft white” bulb that has a comfortable yellowish light similar to incandescents of old will have a color temperature of 2400 to 2700 K (K is for Kelvin). A “clean white” LED bulb that has less yellow and a whiter glow will have a 3000 K rating. “Day light” or “natural white” bulbs will have a 4000 or 5000 K rating. These bulbs, called “cooler” because they have a bluish hue even though they have a higher K rating, look harsh to some viewers but can be ideal in certain situations. I found 5000 K bulbs worked extremely well in lamps that were near a window, mimicking day light on cloudy days. A GE lighting expert told me that folks in the sunny south tend to prefer “day light” bulbs; those in the darker (and colder) northeast tend to prefer yellowish LEDs.

However, brightness and color temperature ratings alone will not tell you how certain colors or shades appear under a particular bulb. For example, while sorting laundry under a 5000 K, 800 lumens Cree day light bulb I found a pale pink shirt looked white but under a soft white 2700 K bulb from Cree with the same lumens rating the shirt was obviously pink. The reason for the difference is how accurately a given bulb displays the full spectrum of light.

So-called CRI or color rendering index numbers are supposed to give shoppers a way to judge how a bulb will look in terms of revealing colors, but the numbers can be deceptive. Both Cree bulbs, for example, had CRI's of 80 (as do most household LED bulbs). But the CRI number doesn't tell you where in the color spectrum the light falls short or may over emphasize a given color. Another design from Lighting Science, for example, has the same CRI as the Cree bulbs but uses a special filter to remove specific wavelengths of light and encourage melatonin production to improve sleep patterns, according to the company.

If color accuracy is very important to you, invest in higher CRI bulbs. These are sometimes called “enhanced spectrum” bulbs or use brand names like GE's Reveal bulbs. These lights have a higher CRI of 90 or more and colors have a crisper appearance under them. But expect to also pay more for high CRI bulbs; a 60-watt replacement GE Reveal LED is just under $20, for example.

Still for all these nuances, even 80 CRI rated LEDs are much more accurate than CFLs. In the future, you may also be able to tune your LED lights, yellow for late at night, whiter for overcast days. In fact, Philips already offers a $200 Hue 3-bulb lighting package that you can program from a smartphone.

In the meantime, there's no reason to buy CFLs, which are yesterday's technology. LEDs are safer, brighter, and better.