Saturday, January 18, 2014

LED Light Bulbs

Recently, I've overcome a bout of laziness and finally got around to replacing light bulbs that had burned out around the house since I first moved in.  I decided to be more energy efficient and spent the extra money on LED lighting, and figured I'd share my research.

If you're not aware, LED lights are the newest type of light bulb available on the market, sitting alongside incandescent (the old style light bulbs that everyone is familiar with) and CFL (compact fluorescent lamp, which are the tube-based ones that have been getting more popular in recent years).  LED lights do have many advantages over the traditional light bulbs; however, as with any new technologies, there are a few considerations that you need to make before deciding to implement LEDs in your home.

First (and foremost!), the entry cost into LED may be difficult to justify.  Incandescent light bulbs are easily found for under $1 each, and even CFL are generally available for around $2 each -- but LED lights still aren't readily available at retail stores, and are significantly more expensive (you may find some under $10, but most are between $10-$20, with some going as high as $60!).  With that kind of price difference, it makes sense to do some cost comparisons.

The chart below shows the features that most people will use in the cost comparison -- the amount of energy they take to produce light, and the expected life of the bulb itself:


Incandescent
CFL
LED
380-460 lumens
40w
7w
6w
750-850 lumens
60w
13-14w
8-12w
1100-1300 lumens
75w
20w
10-14w
1700-1800 lumens
100w
23-27w
12-27w
Bulb life
750 hr – 2,500 hr
10,000 hr
20,000hr
– 50,000 hr

Generally speaking, although the energy use is reduced, the real economical value of the LED over the CFL is the bulb life, at 2-5 times greater – but even then, breaking even financially compared to a CFL bulb is not a guarantee (though it is pretty easy to see that you’ll break even over the traditional incandescent bulb fairly quickly).

The second issue with LED light is fitting into fixtures made for traditional light sources.  Because LEDs are directional, they may not fit well in some of your existing fixtures – especially fixtures that have a base-down configuration.  If the lights  are pointing up, they’ll be distributing the light upward.  That can make the light inconsistent where you typically need it.  Look at the picture from my bathroom below – the light fixture on the left has an LED light in it, and the fixture on the right a standard incandescent.  You can see that there is no light in the bottom of the fixture with the LED – the room still gets filled with light as it bounces off walls, but it is definitely noticeable that you don’t have direct light where you might expect in a bathroom – at the sink and eye level.  Similarly, in base-sideways light fixtures on my bedroom ceilings, the light seems too concentrated at the top of the room.  Light distribution is something that LED bulb manufacturers are focusing on now, and I expect this will be less of a concern in the near future.



There are also some problems related to the base-up configuration of fixtures (though from a light distribution perspective, this is really the best configuration for LED).  The technology for LED bulbs is significantly different from the traditional incandescent and CFL bulbs.  Because the circuits for powering the lights are more centrally located, that area can get very hot.  All LED bulbs have heat sinks to help dissipate the heat from that area, but if the base is up and the fixture is closed, it may be holding all the heat at the point of dissipation.  While the lower energy requirements of the LED bulbs make this less of a safety concern, many manufacturer warnings indicate that base-up configurations may affect the longevity of the bulb, and recommend not putting them into recessed fixtures for that reason.
    
If those issues aren’t as much of a concern, there are still several benefits that you can get from LED bulbs.  Unlike CFLs, they are very close to instant-on.  There is no warm-up time to get to maximum performance, and no need to keep it on for an extended period of time to extend its life (Energy Star recommends that you keep CFL bulbs on for at least 15 minutes to extend the life of the bulb).  Finally, since the LED bulbs do not illuminate in the infrared or ultraviolet spectrums, some insects may be less attracted to LED bulbs than their warmer alternatives (while studies have shown that you will still get some insects that are drawn to the heat and blue light, others will pass for warmer light and more ultraviolet).

With all of this information, I decided to replace all my flood lights and ceiling fan lights (taking advantage of the efficiency of directional light) and lights without fixtures (such as those in my garage) with LED equivalents.  For lights that will be on for longer periods of time and have base-down fixtures, I’ve stuck with CFL bulbs for the time being.

For my bathrooms, I’m still using incandescent lights.  The major consideration that favors incandescent lights in this situation is the color rendering index (CRI).  This is a rating that gauges how well color appears – a scale of 1-100, where 100 is basically how things look in daylight.  Because incandescent bulbs can emit the full spectrum of light, they can achieve a perfect score.  CFL bulbs max out around 80 CRI, and most LEDs are between 75-80 CRI.  While still decent, I am more intrigued by newer LED bulbs that are just coming to market with a CRI over 90 – which should be even better at rendering accurate colors where you may need it most.  In the meantime, I can justify the extra inefficiency of the incandescent bulbs by believing that they’re keeping the chill off as I exit the shower.

And that seems like the ideal image to leave with you.   


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