Which LED bulbs are best for built-in dimmers?

Watch this: In pursuit of the perfectly dimmable LED

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Living in a home filled with dimmer switches can make the lighting aisle seem more intimidating than it ought to be. Sure, plenty of today's LEDs are designed with dimmability in mind, but that doesn't guarantee satisfactory performance. We've heard plenty of complaints from readers, and also experienced first hand the annoyance of spending money on upgraded lighting, only to discover that these fancy new bulbs can buzz, flicker, and dim erratically.

In the interest of making your next trip to the lighting aisle a little less exasperating, we put today's LEDs to the test.

There are lots of things that can cause a light bulb to buzz or flicker when it dims, including things beyond the bulb's control like voltage irregularities, overloaded circuits, and outside interference. The most common issue, though, lies with the dimmer itself, and that's where we decided to start.

Modern dimmers (the kinds you'll find on the shelf at Lowe's or Home Depot) won't actually raise and lower the voltage for smooth dimming, but will instead flash the power up and down at unnoticeably high speeds to create the illusion of dimming. These rapid-fire swings in voltage create electromagnetic resistance in the bulb, which can cause things to vibrate and buzz. You don't want that.

We started with a simple rig using a few common dimmer switches. We chose an LED-compatible model from Lutron, a similar Leviton switch, and a cheap, $5 triac rotary dial intended for incandescents only. Though we aimed for a good representation of what's out there, there are obviously more than three kinds of dimmer switches on the market. As such, your mileage may vary -- especially if you're using an older model, or something more high end.

Interestingly enough, each and every LED that we tested dimmed with all three dimmers, even the one rated only for incandescent use. That lends a lot of credence to manufacturer claims of wide dimmer compatibility -- but it's only the start of the story. As you'll see, dimmable LEDs are not all created equal.

Buzz testing

Dimming annoyances aren't a new problem -- and they aren't a problem that's unique to LEDs, either. The tungsten filaments in most incandescent bulbs are particularly susceptible to the buzz-producing vibration caused by in-wall dimmers. Sure enough, the 60-watt incandescents that we tested out in our rig put out a noticeable buzz across all three switches.

Even without filaments, LEDs have plenty of parts that can vibrate and produce that annoying buzz, and most of the ones we tested did just that, even well-rated bulbs like the Cree 60-watt replacement LED and the GE Reveal LED.

We rated each bulb's buzz on each dimmer using a five-point scale -- very quiet, quiet, moderate, loud, and very loud. The result you want is a bulb that rates "very quiet" across the board, as even a "quiet" buzz can get annoying in a quiet room. For the most part, the buzzing in the LEDs we tested fell somewhere in the middle: fairly moderate, but certainly loud enough to be a legitimate bother.

There were two standouts, though -- one good, and one not so good. Interestingly enough, they both came from Philips. The overachiever was the current generation of the company's standard 60-watt replacement LED, which ran darn near silent across all three dimmers. We couldn't even hear anything when we dimmed it using the cheap, incandescent-only dimmer.

Bookending the other end of the spectrum was the Philips SlimStyle LED, which produced the loudest buzz of any bulb we tested. This makes sense when you consider that in trials like these, buzz is really just a product of a bulb's design. With a radically different shape from the standard, near-silent Philips LED, along with a reorganization of the diodes themselves, it isn't terribly surprising that the SlimStyle's buzz is so much louder.

All that said, it's worth reiterating that we didn't notice an audible buzz with any of these bulbs when using them with standard wall switches, so if you don't use dimmers in your home, then an affordable LED like the Philips SlimStyle might make a lot of sense. However, if you do happen to use dimmers, then spending an extra couple of dollars on something less buzzy might be a worthwhile investment.

The flicker factor

Another problem with the SlimStyle was that it flickered slightly when dimmed low, something we saw in a couple of the dimmable bulbs we tested out. The worst offender was the Switch Infinia 60-watt replacement LED , which flickered badly whenever we dimmed it to 50-percent on any of the three dimmers. We got the same result when we tried out Switch's 40-watt replacement LED, too.

On the positive side, the standard Philips LED once again led the pack. Across all three switches, it dimmed up and down smoothly, never producing a flicker that any of us were able to discern.

Which LEDs flicker the least? (pictures)

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It turns out capturing flickering on camera is easier said than done. After trying a couple of approaches, including slow-motion video capture and pinhole photography, our photographer Colin came up with the idea of examining multiple shots of the same bulb all at once, in grid format. With enough shots, the camera would be able to catch some variance in the light output of a flickering bulb, and some shots in the grid would look darker than others. The greater the variance, the greater the flicker.

This did the trick. A non-flickering bulb like the standard Philips LED produces a grid of photos that all look the same, because the camera wasn't able to catch it putting out different amounts of light at different moments. The contrast with a flickery bulb like the Switch LED, which produced a grid that looked more like a checkerboard, is fairly striking. (You can check out our gallery to compare all of the flicker grids for yourself).

What about smart dimming?

Dimmability doesn't have to come from a wall switch. These days, you'll find plenty of bulbs with built-in dimming smarts -- no wall dimmer needed. Bulbs like these are a terrific option for flexible dimming control, because they'll work with any fixture in your home. Best of all, they're a lot more affordable than you might think.

We've already tested and reviewed several of these types of bulbs. You might be most familiar with options like Philips Hue and Lifx , which offer complete RGB color control in addition to a full, dimmable white light spectrum. Those have their appeal, but you can save a lot of money by eschewing the color-changing novelty factor and opting instead for a simpler smart light.

Of these white-light-only smart lights, the Insteon LED and the Connected by TCP Wireless LED Lighting Kit are two of our current favorites, and the field is only going to get more competitive. Lutron's new Smart Hub for smart dimming control is due out in September, Belkin has Wemo LEDs coming soon, and yet-to-be released options like the Philips Hue Lux and the Samsung Bluetooth Smart LED are even promising to let you dial in to your specific color temperature of choice.

One caveat: if you're going to use a bulb with built-in dimming smarts, be sure that you don't use it with an existing, in-wall dimmer switch. The two separate dimming mechanisms won't play well together, causing your bulbs to flicker and buzz, or worse, not turn on at all. That's the last thing you want to see after spending the money to upgrade the lighting in your home.

If anything, smart bulbs with built-in dimming capabilities seem like the right choice to replace those sorts of old school dimmers. Both for convenience and security, lighting automation makes a whole lot of sense -- and if perfect dimming control is your top concern, you'll love the fact that these bulbs don't buzz or flicker as you dial them down.

Moving forward, CNET Appliances will be giving LEDs the full review treatment -- both smart bulbs and non-connected ones. We'll continue to test more bulbs and more switches, looking for things like dimmer compatibility, buzz, flicker, and dimmable range.

All of it will factor into each bulb's final score alongside things like brightness, color quality, and efficiency. Our goal is to do everything we can to make it easier for you to find the best bulbs for your buck. Stay tuned.