Three LED bulbs, from left to right, the GreenWave Reality, Philips Hue, and TorchStar. At this juncture in the evolution of the LED bulb industry, brands matter, says Katherine Salant. (Mark Lennihan/Assocaited Press)

Over the past 18 months, I have been home-testing LED light bulbs that are intended to replace the residential lighting that we all knew and loved — the 60-, 75- and 100-watt incandescent bulbs that are no longer manufactured.

The good news here, especially for all those homeowners who have not yet embraced the new lighting technology, is that the replacement LEDs, known in the lighting industry as the A19s and A21s, just get better and better. (A19 is the lighting industry’s designation for the shape and size of the iconic 60-, 75- and 100-watt incandescent bulbs. The LED 60- and 75-watt equivalents are the A19 size, while A21 is the designation for the larger 100-watt equivalent LED bulb.)

When I first tested the A19 LED and A21 LED bulbs in the fall of 2012, I noticed right away that the color of the light produced by the bulb varied from manufacturer to manufacturer, even though the wattage and color temperature were the same. The color of the light also differed from that of the incandescent bulbs they were intended to replace. Today, the differences between the three brands that I most recently tested at home — the 75- and 100-watt LED equivalents from Cree, Philips and Sylvania — are only slight, as is the difference between these and incandescent bulbs.

In practical terms, that means you can mix the brands. When you put any two of these manufacturers’ 75- or 100-watt equivalent LED bulbs with the same color temperature in table lamps flanking a sofa or a double bed, only an unusually observant person will notice that they are not exactly the same.

I also found that the light produced by the 100-watt LED equivalents, which is twice as bright as the light produced by the 60-watt equivalent LEDs, worked well for reading. So for the many readers who have asked me about a 150-watt equivalent LED for reading, which is not yet available, try one of those.

Since the first A19 LEDs were introduced in 2010, the rate of improvement in the LED bulbs has been positively dizzying, compared with that of the old incandescents, which were virtually unchanged for at least the past 50 of the more than 100 years they were sold. Even better for consumers, as the quality of the light produced by the LED bulbs has improved, their prices have fallen precipitously.

The first 60-watt equivalent LEDs were made by Philips and went for $40 a bulb. Four years and six generations later, Philips’s 60-watt equivalent is $12 at Home Depot and its SlimStyle 60-watt LED equivalent, which looks like a mini table tennis paddle, also sold at Home Depot, is only $9. Following a similar time and price line, Sylvania’s 60-watt equivalent LED now sells for $15 at Lowe’s. Cree has sold LEDs only for a year; its 60-watt equivalent LED sells for $8 at Home Depot.

The 75- and 100-watt equivalent LEDs, which have more complicated engineering, were introduced later, and for each of these brands, the prices have fallen about 25 to 30 percent in the past year. Currently, at Home Depot, Cree’s 75-watt equivalent LED is $16 and Philips is $20. Cree’s 100-watt equivalent is $20, and Philips is $22. Lowe’s offers Sylvania’s 75-watt equivalent LED for $23 and its 100-watt equivalent for $28.

What else is happening with the A19 and A21 LEDs? At this juncture in the evolution of the LED bulb industry, brands matter. With the old incandescents, all the components were easy and inexpensive to manufacture, and shoppers could expect the same results from any bulb. But that’s not the case with LED bulbs.

The LEDs are hard and costly to make, and it matters hugely who is making them. Cree, Philips and Sylvania all make their own, so each company is able to impose stringent quality controls that produce the pleasing and consistent results I saw in my home testing.

To keep costs down, a Brand X will likely outsource its LEDs and allow a lower quality standard. The light produced by their bulbs may not be the same as that produced by the name brands I tested. To put it another way, you can’t yet mix Brand X bulbs with name-brand ones.

Shoppers do not have to master a lot of technical information before buying an LED bulb, but there is one important difference between the LEDs and incandescent bulbs that every user must learn: the color temperature of the light. Because all incandescent bulbs have the same color temperature — 2,700 degrees on the Kelvin scale — this has never been an issue.

With the A19 and A21 bulbs, there are three color temperatures — 2,700K, which is a warmish yellow and most closely resembles the light of incandescent bulbs; 3,000K, which is whiter and intended to mimic halogen bulbs; and 5,000K, which is bluish, often called “daylight” and usually costs more.

The color temperature may or may not be noted on the front of the package, but it can always be found in the “lighting facts” box on the back.

The differences in the Kelvin temperature of LED bulbs are very noticeable. While you can mix the same wattage of the three brands I tested (which were all 2,700K), you cannot mix Kelvin temperatures.

If you put a 75-watt equivalent, 5,000K “daylight” LED in a lamp on one side of your sofa and a 75-watt equivalent, 2,700K “soft white” LED in the lamp on the other side, you will definitely see a difference, and you might not like it.

GE is now introducing its third generation of A19 and A21 LED bulbs. Its 40- and 60-watt equivalent LEDs debuted early this month and will be available nationwide in Wal-Mart and Sam’s Club by the end of June. GE’s 75- and 100-watt equivalent LEDs will debut in early July and will be similarly available nationwide in Wal-Mart and Sam’s Club by the end of August.

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 .