Historical Light Use Trends

August 31, 2010

I recently came across an article entitled, “LEDs May Not Be So Green.” Since I am in the LED lighting business naturally I was intrigued by this article title. Although I know enough about LED technology to know there isn’t any hidden environmental hazard, I must admit I was a little concerned. The catchy title probably lured in a lot of readers like me, but it really had nothing to do with LED technology. The article discussed the history and patterns of human consumption of light over time. The author argues that the improvement of more efficient lighting technology did not result in a reduction of energy consumption; rather, he argues that people actually consume more electricity because the technology is more efficient. Although I was a little annoyed by the misleading title of the article I read it and gave it some thought.

The article discusses the research of the Sandia National Laboratories, which made many interesting discoveries about our light consumption over the past 400 years or so. Among other things, the Sandia research found that people in the United Kingdom consume 100 times more light today than they did in 1900. The Sandia research also determined that this large increase in light consumption has largely flattened out in the past few decades, which Jeff Tsao attributes to the fact that light output has been stuck at 40-50 lumens per watt for the last 40 years or so. Tsao hypothesizes that the new efficiencies achieved by LED lighting technology will change this and people we will soon see an additional increase in light consumption. This additional light consumption, the article argues, might end up meaning that the improvements in lighting technology will actually be worse for the environment or be “less green.”

I thought about this a bit and realized it made very little sense. First of all, the research measured the consumption of light by measuring the lumen output and found that we consumed an increasingly larger amount of lumens per person until recently. Importantly, this research did not measure light consumption in terms of watts, or the amount of energy which was consumed to produce this light. Isn’t that the whole point? That we need to generate energy to produce light which can be harmful to the environment? We aren’t talking about light pollution. And if this is the case, why does it matter that we consume more lumens than we used to, or that we might consume more lumens yet because of LEDs? If we can consume more lumens and use less energy, does it matter at all that we are consuming more light? I think it does not.

The study, and conclusions made by the author, also make some assumptions that don’t have any factual support. One such assumption seems to be that there is a nearly infinite demand for light, if the cost of light is low. I think the simple fact that people need to sleep, and are unlikely to do so with all the lights on, is a simple fact which contradicts this assumption.

I also have some recent personal experience that may shed some light on this. We recently moved into a new house, which has several built in light fixtures. All of the lights were outfitted with incandescent light bulbs. I replaced all of these light bulbs with either CFLs or LEDs. I tried to use LEDs in the light fixtures that we use more often, to maximize the savings from the new light bulbs. In many instances, I was replacing a 75 watt incandescent with a 2.5 watt LED. Although, I have no urge to leave these lights on all the time simply because I am using so much less power, I think it is important to point out that even if I left these lights on 24 hours a day I would still consume less power than using the 75 watt bulb for one hour. Although the differences in efficiency between the CFL and incandescent bulbs isn’t as great as that between the LED and incandescent bulbs, one would still have to work pretty hard (and have a complete disregard for power consumption) to use more power with a CFL than an incandescent.

Even though I think the conclusions made by this article are not correct, I do think that it makes sense for consumers of lighting products and energy, to make sure that we do not use improvements in lighting technology as an excuse to waste energy, or as a reason to get lazy about our efforts to conserve energy.

In the case of LED Christmas lights, the average user will use anywhere between 70% and 90% less energy. This doesn’t mean that after making the switch to LED Christmas lights, the user should strive to use the lights 70% to 90% more, or use 70-90% more lights. Although the extreme efficiency of LED Christmas lights allows the user to use more lights for longer and still use much less power, we think it makes more sense to use LED Christmas lights wisely. This means using timers, so that the lights shut off at night when no one is viewing, as well as taking other similar responsible actions to conserve as much energy as possible.