Five things you didn't know about LED lightbulbs

LED bulbs are energy-efficient and designed to last for many years, but here are a few lesser-known features to consider when weighing a jump to LEDs.

Martin LaMonica Former Staff writer, CNET News
Martin LaMonica is a senior writer covering green tech and cutting-edge technologies. He joined CNET in 2002 to cover enterprise IT and Web development and was previously executive editor of IT publication InfoWorld.
Martin LaMonica
5 min read

If you've heard about residential LED lightbulbs, you probably know that they're energy-efficient, last a long time, and are pricier than other lightbulb technologies.

I've been using LED lights in my home for several months now, and overall the transition has been good. As you consider your lighting options, here a few things that you might not know about LEDs.

LEDs are cooler.
When you're running fans or an air conditioner this summer, having burning-hot incandescent bulbs just makes it harder to manage the heat. LEDs run much cooler than incandescent bulbs and significantly cooler than CFLs.

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Online retailer EnergyCircle actually measured the difference and found that a halogen bulb, a type of incandescent bulb, ran at 327 degrees! A Cree LED downlight was measured at 107 degrees and a Philips Par38 CFL worked at 167 degrees.

That's not to say that heat isn't at all an issue. LED bulbs do get hot but the heat is dissipated by metal heat sinks that wick away the heat from the light source itself. Keeping them cool with heat sinks or even liquid cooling, as Switch Lighting is doing, is important to ensuring they last as long as advertised.

You get instant full light.
You get the full brightness of an LED bulb when you turn it on, which is an advantage over CFLs in a couple of ways. For starters, you don't need to wait for full light if you're running in and out of a room. But frequent cycling also degrades the life of CFLs, one of the reasons that CFLs in some cases don't last as long as expected.

I've become more conscious of this and put LEDs in places where lights are cycled on and off quickly. CFLs, meanwhile, are in light fixtures and lamps which typically stay on for extended periods. Consumer Reports found turning CFLs on and off in less than 15 minutes degraded their life.

LEDs don't attract bugs.
Pixi Lighting, which makes LEDs, lists "no bugs!" (that is, insects) as one of the reasons to use LEDs. But if you look at discussions online, it's not so clear-cut.

The stated reason that bugs don't fly toward LEDs is because bugs are attracted to ultraviolet light and at least some LEDs don't give off this type of light. But that's not universally true for all types of LEDs, according to people who have commented online. In one discussion, an employee from EnergyCircle said that most residential LED bulbs give off almost no UV light.

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In an unscientific test last night at my house, I saw moths and mosquitoes fly right past my outdoor LED bulb; they were not attracted to the light. Consumer LED bulb maker Pharox advertises its bulbs as having no UV, so it's something worth checking when you're shopping around.

LEDs come in funny shapes.
Lighting manufacturers have tried to make LED bulbs as familiar-looking as possible, most importantly by having a screw-in connector. But there are limits to mimicking the Edison-style bulb.

"Snow cone" LEDs, where the top half is a bulb shape, best resemble incandescent bulbs but light is given off in only one direction. So you'll get more light from the top of a desk lamp, for example, than the bottom. CFLs or incandescents give off light in all directions.

The most recent bulbs to come to market address this light dispersal problem very well. I've been testing a Lighting Sciences Group 60-watt equivalent for the last week or so and it does indeed give off far more even light than the company's own snow cone-type bulbs.

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The price for the more even light dispersal is odd-looking bulbs. The LSG bulb has a squat disk for a light source and the rest of the bulb is a heat sink made of metal fins that make up most of the actual bulb.

Philips' LED bulbs have a crown-like light source and a similar aluminum heat sink. But their recently released 75-watt equivalent bulb has a noticeably longer heat sink than the 60-watt equivalent Philips LED, which is something to consider. When I tried it at home, the 75-watt equivalent, called the 17-watt A21 LED, was too long to fit into a small overhead fixture.

You will need to learn some lighting lingo.
We still talk about 60-watt and 75-watt equivalent bulbs because that's what we're accustomed to. But some manufacturers are using new labels that give people far more information than brightness, which is worth understanding as lighting gets more diverse.

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Lumens, of course, measure the amount of light, with a 60-watt equivalent giving off at least 800 lumens. But LEDs are also sold by color temperature, either warmer yellow light or cooler white light. And then there's color rendering index, with the highest being the best for light quality.

Warmer color lights will be more familiar since they're closer to the yellow glow of a CFL or incandescent. But I found I like the cooler, white light of the Lighting Sciences Group bulbs, rated at a cooler 3000 Kelvin, which I find a little cleaner. As for color quality, I can't put my finger on why, but I've been very happy with the light from a Pixi bulb which has a 96 color rendering index--higher than the others I have.

Bonus: 40-watt equivalents bulbs are underrated.
Some of the first general-purpose LED bulbs I tested were rated with the light output of a 40-watt equivalent. I found that they were not quite enough to light up a whole room, but they do the trick in more places than I thought. For example, I have a small LED for an outdoor light and one in the basement. These aren't spots where I'll spend time reading a book so these energy-sippers have fit in nicely.