Philips recently introduced SlimStyle, a new 60-watt LED equivalent design that eliminates the tell-tale heat sink of current LED bulbs. (Ian Hardy/Countdown Entertainment)

Some months into the new year, you will notice a big change in the lighting aisle of your local retailer or big-box store.

The supply of 40- and 60-watt incandescent bulbs that accounted for 80 percent of the residential lighting market in the United States and occupied the most shelf space will be low. Their production will cease on Jan. 1. Once the existing inventory is sold out, it will be gone for good.

These iconic bulbs, known as the A19 bulb in the lighting industry, have been fixtures in American households for more than 100 years. But, despite their long history of reliability and low cost, they are hugely inefficient. Only 10 percent of the energy consumed by an A19 incandescent is given off as light; the other 90 percent is heat. For this reason, the Energy Independence and Security Act of 2007 mandated their phaseout. The 100-watt bulbs were phased out in 2011, then the 75-watt bulbs in 2013.

In response, the lighting industry has developed a new type of energy-efficient bulb — the light-emitting diode, or LED. In the 40- and 60-watt equivalent category, every major bulb manufacturer offers several A19 LED alternatives; major retailers have their own house brands as well.

For the conversion, manufacturers largely are designing the new bulbs to look and act a lot like the old ones. But some are offering a window into the possibilities of high-tech lighting when the bulb will become more like an electronic device.

Philips has already developed a bulb that allows you to wirelessly vary the color of the lighting from standard white to shades of blue, yellow, red and green and create a mood as you settle into a comfortable chair after a hard day’s work, drift off to sleep at the end of the day or have a few friends over to share a bottle of wine. Also get ready for unconventional shapes and sizes.

What can you expect from the A19 LEDs? To find out, I home-tested 13 A19 60-watt replacement LEDs from four manufacturers — GE, Sylvania, Philips and Cree (an established LED manufacturer but a new player in the A19 LED arena) — and two house brands, Lowe’s Utilitech Pro and Home Depot’s EcoSmart. I compared these to each other and to a 60-watt incandescent bulb. By the end, much to my surprise, I came to prefer the LEDs to the old-style bulb.

Read the packaging

Though I had a few favorites, all the LED A19 bulbs that I tested produced a quality of light that most households will find highly acceptable. The manufacturers, chastened by consumers’ initial experience with another energy-efficient A19 alternative, have worked hard to make the initial experience with an LED a positive one. (The first compact fluorescents, or CFLs, produced a color of light that many people found unpleasant. The bulbs also took as long as 30 seconds to reach their rated wattage, and they couldn’t be used with dimmers.)

To make the transition easier, the iconic shape of the A19 bulbs has been retained, but the purchase of an LED will not be as simple as it was with the old-style bulbs. There are significant differences, but the buying public should find them easy to master.

The most important one is the color temperature of the light. This has never been an issue with the incandescents because they all have the same 2,700 K, or 2,700 degrees on the Kelvin scale.

A19 LEDs, however, are manufactured in three different Kelvin temperatures: 2,700 K, which has a slight yellowish tinge; 3,000 K, a crisp white that appears to be brighter than the 2,700 K even though the actual wattage is the same; and 5,000 K, which is slightly bluish and often called “daylight.” In my home testing, I only looked at 2,700 K and 3,000 K LEDs because these are the closest to incandescent light.

The 2,700 K, 3,000 K and 5,000 K color difference is a distinction that most people will notice, so it pays to check the packaging before you buy. It may be prominently displayed on the front or buried in the “Lighting Facts” box on the back under “Light Appearance.” The Kelvin temperature will be indicated on a lighting scale. Somewhat counterintuitively, the “warm” color temperature at the left end of the scale is actually cooler, and the “cool” color temperature at the right end is hotter.

To keep the Kelvin color temperature straight, recall your middle-school astronomy lesson: Old stars are red and cooler, new stars are blue and hotter.

Another difference between the A19 LEDs and incandescents is the color-rendering index, or CRI, a measurement of how the colors of objects illuminated by a given light source appear to the human eye. Color is truest with sunlight, which has a CRI of 100; incandescent bulbs also have a CRI of 100. Most A19 LEDs have a CRI in the 80 to 83 range, very workable for most applications.

In some instances, however, extremely accurate color rendition may be important — for example, a dressing area where you are selecting outfits for work or an important social occasion or a bathroom where you are applying makeup. For this, you might consider Cree’s TW Series A19 LED, available online at Home Depot, which has a CRI of 93. For more general lighting situations in which you want colors to appear more vibrant, GE’s A19 LED Reveal has a CRI of 90.

High price, long life

The first thing you will notice about A19 LEDs in the store, however, is the price — it can range from less than $10 to more than $30. This will be a shock when you’re used to paying a $1 or less for an incandescent, but there is a very big upside here.

An A19 LED bulb lasts 15 to 25 times as long as an A19 incandescent, and that’s just its rated lifetime. Unlike an incandescent, which burns out after about 1,000 hours, the A19 LED will still be emitting light after its rated lifetime of 15,000 to 25,000 hours. At this point, the emitted light must be at least 70 percent of its initial brightness, but it may be much higher.

When Philips’s A19 LED was run for 25,000 hours straight (this took two years and 10 months) by the Department of Energy, the bulb was still emitting light at 100 percent of its original brightness. The manufacturers do not yet know when the light emitted by the A19 LEDs will be too faint to be usable because the technology is too new; theoretically, several engineers said, the bulbs could last another 25,000 hours.

The rated life of the A19 LEDs in the “Lighting Facts” box on the package will be given in years, not hours. For most A19 LEDs, the life will be 22.8 years if used three hours a day, the average use per bulb per day in U.S. households.

How long will an LED last in your household would of course depend on your own usage. For example, if you find you’re using an incandescent bulb in a busy area like a front hall for about eight hours a day and changing it about every four months, an LED in that same spot would be at its rated 25,000 hours after eight years and eight months, and it will still work.

And you would be saving money because the A19 LEDs use 80 to 84 percent less energy. According to Pepco engineers, the difference in cost between purchasing and using one LED, and purchasing and using 25 incandescents over the eight-year, eight-month period, would be $114 (assuming an electricity rate of 8 cents per kilowatt hour, a cost of $1 per bulb for the 25 incandescents and $13 for the LED).

In many areas around the country, the initial cost of an A19 LED with an Energy Star rating has been offset with rebates from local utilities that can be as high as 50 percent.

Locally, Pepco is participating, Dominion is not. The Maryland program is run by Pepco with rebates at both large and small retailers.

For a complete list of participants, go to and scroll down below the map. In the District, the DC Sustainable Energy Utility runs the rebate program. For a complete list, go to , scroll down to “find a store” and put in your Zip code.

Katherine Salant has an architecture degree from Harvard. A native Washingtonian, she grew up in Fairfax County and now lives in Ann Arbor, Mich. If you have questions or column ideas, she can be contacted at or .