After we published the results of those tests, Philips sent us some additional bulbs, telling us that the newest versions of the SlimStyle might perform better with dimmers than the release-day bulb we had tested. If there is a performance difference, it's a fractional one, and not one that we were able to detect. On our dimmer switches, the newer SlimStyles still buzzed, and they still showed a light amount of flicker, same as before.
All of this is to say that if you're buying a bulb for use with a dimmer switch, you'll want to go with something other than the SlimStyle. The best choice would actually be Philips' own standard 60W Equivalent LED, which aced the same dimmability tests that the SlimStyle flunked. At $15, that bulb costs a fair deal more than the SlimStyle, but I think it's worth it if you want smooth, dimmable light with no flicker or buzz.
Another bulb-buying consideration has to do with the heat generated by the circuitry inside. Just like with your phone or laptop, this heat will affect the bulb's performance, which is why LEDs put such a strong emphasis on thermal management.
When you first turn an LED on, there isn't any heat, so the power and light output that you see should be at something close to an optimal level. As the bulb heats up, generally over the course of about 30 minutes, the power output will diminish very slightly, until the bulb plateaus at what manufacturers call the "steady state."
Before you cry foul, keep in mind that the decline in light output is only barely noticeable, if at all. Also, LEDs don't get rated for brightness or efficiency until after they've hit their steady state, so you aren't getting shortchanged on specs.
With our spectrometer, we can track an LED's visible power output over time, then graph that steady state for ourselves, and we decided to do just that. The purple line in the graph above represents the Philips SlimStyle's power output over time, and as you can see, it does a great job, flatlining at around 92 percent of its initial brightness.
That's a higher steady state than any other bulb we've tested, and the only one we've found above 90 percent. Results like that suggest that heat doesn't affect the SlimStyle's performance as much as it does with other LEDs, which lends some credence to the bulb's unique design.
The practical takeaway from this is that the Philips SlimStyle might be an especially good choice for use in enclosed fixtures. Trap a bulb inside a fixture, and you're trapping it with the heat it produces, which can lower the steady state and potentially reduce the bulb's lifespan, too. A bulb like the SlimStyle, which manages heat particularly well, stands to suffer a lot less in settings like this than other LEDs.
At $9 each (or lower, if you live in a region that offers instant rebates for Energy Star-certified light bulbs), the Philips SlimStyle offers plenty of light bulb bang for your buck. You won't have any problems with its brightness or color temperature, and if you're switching over from incandescents, you certainly won't be complaining when your next power bill arrives.
That said, for a dollar more, the Cree 60W Replacement LED offers an uptick in efficiency, along with a 10-year warranty that's more than three times what you'll get for the SlimStyle. And for ultimate value, the $5 Ledare LEDs at Ikea are awfully tough to beat -- although their diminished brightness and lack of a warranty stop me from recommending them outright.
If you're looking for a bulb to use with a dimmer switch, you'll want to look elsewhere, as the SlimStyle tends to buzz quite a bit more than other LEDs whenever you dim down to 50 percent or lower. On the other hand, for enclosed fixtures -- globes, sconces, and so on -- the SlimStyle seems to be an ideal option.