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Consumer Interest Inquiring Minds

Inquiring Minds Want to Know: Do you save energy by dimming LED bulbs

Intro

I’ve got my Philips Hue light bulb working with my Amazon Alexa. It’s an older 860 lumens bulb. I also have a voltmeter. So I went through different intensities, recording the power draw for each. The results are in the table below.

Level (%)Power (Watts)
1009.0
907.0
805.7
704.3
603.4
503.1
401.7
301.2
201.0
100.8
0 (off)0.3*
Power draw of LED light bulb at various brightnesses set by Alexa voice command.

So above 60% or so the relationship looks exponential. 50% seems like an outlier.

*Unexpected finding – smartbulbs are vampire devices

I didn’t originally measure the power draw when “off.” You don’t think to do that. Then I gave it some more thought and had an aha moment – the bulb can only be smart if it is always listening for commands. And that, in turn, must create a power draw when off. A quick measurement and sure enough, confirmed. Though very small – 0.3 watts – it is not nothing. A typical single-family home has over a hundred bulbs. If they were all smartbulbs, it would add up… I believe small draw devices – typically those power adapters for cell phones – are called vampire devices.

Conclusion

So we have a very non-linear relationship here. I probably should plot the current draw as well. But, you definitely can save energy by lowering the intensity – quite a lot. But LED bulbs are drawing very little power anyway, so unless you have bunch of them, why bother?

My second conclusion – a finding I didn’t expect – is that even when off these bulbs are consuming a bit of power. It’s not a lot, 0.3 watts, but it’s something to keep in mind when planning your smartbulb deployment. So, large arrays of smartbulbs? Probably not such a smart idea.