Karen Nakamura: July 2010 Archives


When I was in Japan, I replaced a couple of my mother-in-law's ceiling lights with LED bulbs. They are the big thing now in Japan, which is trying hard to meet the Kyoto protocol guidelines.

Coming back to the States, I thought I'd replace the few remaining incandescents and some of the CFLs (compact fluorescent lights) in my house with LEDs.

In comparison to incandescents:

  • Much better efficiency
  • Produce much less heat
  • Much longer life (10,000 hours vs. 1000 hours)

In comparison to compact fluorescents, LED have:

  • Marginally better efficiency in their current iteration*
  • Require almost no warm-up time to maximum light**
  • Work great in the cold
  • Have no toxic chemicals such as mercury in their construction
  • Generate no UV or IR rays
  • Much longer lifetime (50,000 hours vs. 10,000 hours), especially in situations where there is a rapid on-off cycle which is very harmful to CFLs

I'm experimenting with a few different sources. I bought some E27 (edison screw-in) bulbs from China, have a PAR30 "can" size reflector on order from an eBay vendor  and just ran down to Home Depot and got their new $20 EcoSmart LED bulbs.  I'll be putting them through the wringer and let you know what I think.

So far, the EcoSmart (pictured right) with 420 lumens @ 8.6 watts (49 lm/w) seems a good price/performance leader at $20 a bulb. The light it emits is a nice warm white, rather than the very bluish light that the Chinese bulbs are giving me. And it's dimmable, which is surprising given its low cost. It's working fairly well with the Lutron dimmers in my house.***


* Everyone thinks that LEDs are much more efficient that CFLs. That's true as a general proposition under optimal conditions (Cree is getting 200 lm/w in the lab) but the LEDs in these household bulbs are usually overdriven in order to put out as much light as possible. The LED bulb above is only getting 49 lm/w  where as a 16 watt CFL usually puts out 800 lumens, which would be 50 lm/watt.  In comparison, an incandescents gets around 7-24 lumens per watt.

** While LEDs themselves light up at 100% brightness instantaneously, I've found that must of the bulbs I have require around 0.25 seconds for the LEDs to turn on from when the switch is thrown. Most likely the internal LED drivers require a minute amount of startup time.

*** My standard Lutron dimmers (Maestro series) expect a certain amount of resistive load. They're rated for 600 watts, but if you use all LEDs (or CFLs), they may see less than 50 watts on the  circuit. The Lutrons end up flickering at low dim levels -- or acting bizarrely. So I've had to retain a single incandescent on my dimming circuit. This doesn't make me happy, I'd like to switch to all LEDs -- but in order to do so, I'll have to switch out my dimmers.

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This page is a archive of recent entries written by Karen Nakamura in July 2010.

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