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Posted by on Feb 28, 2013 in Evironment, Life, Technology | 17 comments

LED vs. CFL vs. Incandescent Light Bulbs

I’m building a new house right now and one of the areas of concern is electricity cost.  We use Green Mountain Energy which is 100% wind power.  (Yes, I know my electricity comes from the Texas grid which has gas and coal and nuclear plants.  However, my money goes to the wind farm, not to the other power sources.)

I’ve been thinking that I want to go pure LED (light emitting diode).  There are several reasons.  The first is that the run cooler than any other light bulb.  At night, in Texas, in the summer, sometimes the temperature almost drops all the way to 90ºF.  Believe me, there is a difference between sitting in a room with incandescent bulbs and one with CFLs.  The second is electricity cost.  The third is using less electricity (related to cost).  The final point is that LED lamps tend to run at a higher color temperature.  This last may need a bit of explanation.

There’s a concept in physics called a ‘black body’.  I won’t go into details, but the frequency of radiation (light) emitted by a black-body depends directly on the temperature (in degrees Kelvin) of the body.  So a black body radiator that is at a temperature of 2,000K emits an orangish light, while one at 10,000K emits a bluish light.

Incandescent bulbs emit light between 2,000K and 3,000K.  So the light looks orange or yellow to us.  These are called ‘warm colors’.  It’s an artist thing about how the light makes you feel when looking at it.  Yellows and oranges make you feel warm.  Contrast that with a light emitting a bluish light which makes you feel cool, like a compact fluorescent bulb.  These can range in temperature from about 3,000K to 6,700K.

Sunlight is filtered and scattered in our atmosphere, but a clear day with sun overhead is roughly equivalent to a 6,500K black body.  While if you look towards the pole (perpendicular to the sun) on a clear day, you might get all the way up to 15,000K color equivalent.

I live with an artist, so true color is psychopathically important in our house.  LEDs and compact fluorescent (and some other fluorescent bulbs) can reach the 6,500K mark.  Look for ‘daylight’ bulbs.  They are pretty popular now, but make sure it has the color temperature on the label.  Some places are selling 3,000K bulbs as ‘daylight’.  Here’s a hint, people who grow things that need actual daylight (indoor gardeners and reef aquarium keepers) use lamps at a minimum of 6,700K and all the way up to 20,000K .   And, I just prefer cooler light… again that may be just living in central Texas.

Now, how does this apply to light bulbs.  The house is LEEDS certified and Energy Star and all that stuff. Some of the LEEDS certification comes from building efficiency, more efficient HVAC systems, better plumbing, more insulation, etc.  But part of it is a reduction in the used electricity.

According to several sources, a modern home (within the last 5 or 6 years) will cost up to half as much to operate (heating, cooling, electricity, water) as a house built just ten years ago.   Lights are a small part of the improvement.

Think about the room you use most often (kitchen, office, whatever).  In my current bathroom, there are 6 60-Watt incandescent bulbs providing light.  They are in use about 4 hours per day (me, wife, kid bathing and dressing).  That’s

6 * 60-Watts = 360 Watts

* 4 hours = 1440 Watt hours per day

or /1000 = 1.4 kilowatt hours per day.

Times 365 days = 525.6 kilowatt hours per year

at $0.10 per kWh = $52.56 per year in electricity… for that ONE room.

It also makes the room quite warm, which for the 8 days a year that it’s cold in central Texas (and I mean anything below 50°F is cold)*, otherwise it’s just more to cool off.  At least one source says that a 100W incandescent bulb hits 375°F.  I haven’t tested it, but it seems reasonable to my burned fingers.  Compact fluorescent and LEDs just don’t get that hot.  They don’t convert electrical resistance to light like a incandescent bulb does.  Resistance generates heat.  Up to 90% of the electricity going into an incandescent bulb is turned into heat instead of light.  For that 100W bulb, you’re getting 10W worth of light and 90W worth of heat.

I haven’t mention halogen bulbs (or any of the other weird bulbs like High Intensity Discharge or metal halide) because they are either way too hot (metal halide and halogen) or need special UV coatings (HID) or they are just not appropriate for home use (sodium vapor).  I’ve seen both halogens and metal halides in home use and, no doubt, they pump out light.  But they are just so hot.

Let’s talk about light for a second.  Light is measured in lumens. A lumen is the total amount of visible light emitted by something.  I won’t go into candelas and steradians here.  But you can get more at Wikipedia if you like.

When every lamp was an incandescent, it didn’t really matter how they were measured.  A 75W bulb was less bright than a 100W bulb.  But now that we have all these super-efficient bulbs it makes sense to talk about how much light is actually produced by the bulb.

Now, the industry is using lumens to measure how much light the bulbs produce.  A 60W incandescent lamp may push 800 lumens, while a CFL only needs 15W and an LED only needs 10Ws.  A 10W incandescent is a night light.

If you are thinking about changing, look at your space and decide if you want more light, about the same, or less light.  Then decide if you want warmer light or cooler light.  If you have 6 60W bulbs in your bathroom, that’s about 4800 lumens.  About 6 10W LEDs will produce the same 4800 lumens.

One note about this.  LED lights have two properties that need to be taken into consideration.

The first is that LEDs are highly directional.  Unlike incandescent and CFLs, they only emit light in one direction (usually a hemisphere).  Even incandescent spot lights emit light in all directions, just some is reflected back by a coating on the glass part of the bulb.  So LEDs tend to act as spot lights and, in a certain area, may be brighter than you expect while everywhere else tend to be dimmer than you expect.  They are really good for task lighting (and they don’t get as hot).

The second is that LEDs are point sources not diffuse sources like the other light bulb types.  You can get some strange effects in water, reflections, and the like with LEDs.  If you’ve ever been underwater and seen the shimmer effect that the sun makes in the water, you know what I’m talking about.  LEDs do that.  It can be unsettling when you first realize it, but you get used to it.

Let’s say that I replace those 6 bulbs in my bath room with CFLs.  I need

6 * 15W bulbs = 90W

* 4 hours = 360Wh or

/1000 = 0.36 kWh per day

* 365 days per year = 131.4 kWh per year

* $0.10 per kWh = $13.14 per year

A difference of almost $40 per year in electricity savings.  A good CFL will set me back about $4 per bulb (for a really top of the line one).  The electricity savings alone pays for the bulbs in less than a year.

Using LED bulbs is roughly the same.  You save an additional $4.00 per year, but the bulbs themselves are much more expensive.  The prices are coming down though.  And they are rated to last 50,000 hours, while CFLs are rated for 10,000 hours and incandescents are rated for about 1,000 hours.  To give you an idea, 50,000 hours is 17 years running 8 hours per day.  I’ve been in our current house for five years and never replaced the CFLs that came with the house, but I’ve replaced every incandescent bulb at least 3 times.

Here’s my plan for our new house.

The first thing will be to replace whatever lights that are incandescents with either CFLs or LEDs, depending on the function of the light.  Bathrooms and general light will be CFLs while task lighting, pendants, etc will be LEDs.  As the CFLs need to be replaced, in 5-6 years, I can changes those to LEDs.

The can lights in the ceiling will be replaced with LEDs immediately.  First, they need to be spot lights rather than flood lights.  Second, can lights run hot anyway and need to be cooler.  Third, they are a pain in the ass to replace and I never want to do that again after the first time.

 

 

________________________
* Scoff if you will all you Yankees and Canadians and other people who shovel snow.  I’d like to see you survive 30 days of 110ºF+ in a row.

  • DRC

    It’s important to consider the Colour Rending Index (CRI) of white LEDs. There could be 2 LED lights on the market both rated at 6500K, but the one with a higher CRI will more faithfully recreate 6500K. Higher CRI lights look better but often cost more, and may be less efficient.

    http://en.wikipedia.org/wiki/Color_rendering_index

  • sstar

    I’m in the LED business, everything you said is true. I would just like to add

    1) CFL lamps are also very sensitive to on/off switching which reduces lamp life. You should take this into consideration. LED lights don’t suffer from this. They also contain mercury which isn’t great for the enviroment.

    2) Also please take note of what type of LED Chip is being used. There is a wide range of chips on the market and some have a low lumen/watt ratio.

    3) If you are in the process of planing take note of the degrees of aperture of the lenses for spot lights. Tighter angles will give more light in smaller areas.

    4) For indor gardens there are special LED lamps that have the colour temperature set at specific photosithisis range which is red blue light at around 612nm and 412nm respectivly.

    Let me know if you need any info on any particular LED

    • Dinah Kirkpatrick

      Is there anyway to use LEDs in all of the cans without making it look like spotlights? Do we need to have more cans and space them closer together to get a wash?

      • SmilodonsRetreat

        There are LED flood lights. I don’t have any right now, but they exist. More cans would probably just give you more spots on the floor. Try (or find a light store that has one in a display) to find the LED floods.

        Hope that works.

  • rg57

    Several years ago I purchased some “daylight 50″ CFLs for my home, in part so I wouldn’t look orange on my webcam (turns out I should just have waited for cam software to mature). While I don’t regret the significant energy savings, the color temperature was a massive mistake. It is depressingly stark in an indoor setting. Further, if you make this mistake with CFLs or LEDs, they take forever to die and you’re stuck with them for years. For most of your living area I’d recommend choosing something between soft white which you want to avoid, and the depressing D50 that I urge you to avoid. Perhaps a mix of color temperatures depending on location and application is best. As my daylight CFLs are burning out (literally, in some cases!) I am replacing them with LEDs of a warmer color temperature.

    (I can only assume that the “cooler light” bulbs consume slightly more energy to achieve the same brightness, due to both the higher frequencies required, and also the reduced number of blue cones in our eyes relative to the rest… but maybe it’s insignificant … but maybe not over 17 years…).

    * I did 24 days of 100ºF+ in a row in north Texas. Is that close enough?

  • SmilodonsRetreat

    All excellent tips. Thanks.

    sstar, are the CREE chips still the best? Are there standard screw in bulbs that use those chips, especially in the flood light category?

    rg, I’m not sure what daylight 50 is. I have heard that CFLs can actually burn out sometimes. And you’re right, a mix would probably be best. Pure daylight for the task lighting, especially in the studio (we have 6700K T-5s in there now) and warmer lights in the high cans and such. Good advice.

  • sstar

    Yes CREE chips are still the best, but Seul Optical also makes good chips. Keep away from Edison chips.The range of lamps is almost complete. There are standard screw in bulbs, spot lights, flood lights, T8/T5 tubes…

  • http://disnotblog.blogspot.com/ Eugen

    Interesting cost analysis Smilodon and good timing.

    I’m in the middle of redoing kitchen and installing recessed fixtures (cans, pot lights).

    I would like to ask sstar couple of questions.

    How do we find out which chip is installed inside a light-bulb? What LED manufacturer would you recommended for PAR20 type bulb?

    • sstar

      Hmm that’s a good question the problem is that there are many many manufacturers of lamps most are Asian and most if not all don’t say what type of LED’s are used. The only way to check is to pick out the model and check on the internet. What makes matters worse is that sometimes producers indicate that they use one chip when they actually use another. So in the end it’s actually a nightmare. Lastly keep away from big name brands like philips/osram etc… aside from being very expensive the lumen/watt ratio is very bad. These companies have no interest in selling LED lamps for obvious reasons (if they sell you a lamp that’ll last you 10 years what are they going to sell you next year? Besides they need to pay off their flourecent industries first.)

      So in the end all I can suggest is that you do the following test:

      Best LEDs have 90% saving over halogen / incandescent in lumen / watt ratio. That means that a 6 watt LED par 20 spot light should be equivalent to a 45-50 watt halogen par 20 spot light. Test the two together if the light is a lot less it’s using low quality LED’s. Be sure to be testing lamps that have the same beam angle aperture and preferably the same colour temperature. Also note that LEDs emmit 7-10% more light in the cold colour temperatures.

      • http://disnotblog.blogspot.com/ Eugen

        ” Besides they need to pay off their florescent industries first ”

        Very good point.
        Thanks sstar , I will follow your advice and do some testing and reading.

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  • http://illustralighting.com/ Cassandra Allen

    Excellent points there. LED technology still has a long way to go and has lots of room for improvement, which makes it a better bet unlike CFLs that seem to have reached its peak yet some concerns, especially health and environmental ones, haven’t been sufficiently addressed yet. Here’s a comparison of current LED and CFL bulbs that might help clarify where these two lighting technology stand today – http://goo.gl/JrwuE

  • tock

    Thank you for all of ths. I am converting a bedroom to an art studio. 9′ ceiling. I have not yet installed the lights. A nearby 9′ ceiling room has LED cans installed and I put an easel under it and was aghast at the number of shadows under my hand when stretched toward the canvas. Shadows of my head also fell on the canvas from several sources of LED lights spread behind me. So I appreciated learning from you that LED lights are more of a spot light, although i was happy with the color rendering of these 3000K LED lights even though it was only 83 CRI- they seemed good enough for me. I am not a fan of that blue look! And let’s be serious. I’m not Monet! (who probably worked in his studio at night under incandescent lights, but who also went blind, so there ya go).

    My current art studio is in the garage, i’ve used one warm and one cool florescent tube and it has actually worked pretty well. Aside from looking like a garage workshop, I’m almost tempted to put this into the new studio, but was wondering if maybe the better idea would be:4 independently controlled recessed canned lights; 2 of them CFLS, 2 of them LEDs. I would use the LEDs on one side of the room to light up my work desk. I think that would be ok (maybe kinda shaddowy though?). the other half of the room is where i stand to paint, and I’d put CFLs there so the light spreads and doesn’t cause the shadowing. Would y’all agree (< trying to speak my best texan there!) Let me know if you have ideas…. work in progress this week, but I'll take your answers when you can! Thanks!

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  • Casey

    3M has recently manufactured an excellent bulb- the 3M Advanced LED Bulb. These are NOT directional in the least, as they use fiber optics to evenly distribute the light. They also come in a “warm” And a “cool” version.

  • markvturner

    FYI, cool white and daylight bulbs can mess up your circadian rhythms, causing you to have trouble falling asleep at night.

    I tried using a few 4000K bulbs in my bedroom for like a week. The color looked great, but I was up until like 2am-3am all the days I tried using them, cause the light was keeping me awake and alert.

    I now use ordinary 2700K incandescent & halogen bulbs in my main lighting fixtures. I live in San Francisco where it’s chilly when the sun is down, so the heat output is welcome, and reduces the load on my electric space heater.

    I have a separate floor lamp with a super bright 5000K CFL bulb that I use in the morning. It uses 105W and puts out a whopping 6600 lumens, which is the same as 400W of incandescent lighting. It’s very invigorating, and great for waking me up in the morning.

  • jungle jim

    In your case the decrease in heat production saves in cooling costs. What about those of us in cold climates? I haven’t seen any estimate for increased heating costs because of the loss of heat produced by incandescent lights.

    • Shiloh

      I think that’s irrelevant because you’re paying for the heat generated by the incandescent bulbs anyway, so any increase heat your furnace must put out due to switching bulbs is really a transfer of cost, not increase in cost. And if your furnace operates on a fuel more expensive than electricity in your area, well, a 1500w space heater will put out more heat than 1500w worth of incandescent bulbs.

  • Doctor Girlfriend

    Certainly, people have their opinions on Walmart, but cost is no longer an argument against CFLs if you’re willing to purchase wally world’s store brand CFLs. A four pack of the 14W (60W-equivalent) daylight style (5000k) bulbs is a mere $2.50 locally, and the standard, soft-white (3000k) are even cheaper than that. By contrast, the store-brand 60W incandescent bulb four pack is $1.00 locally.

    There really is no reason whatsoever to chose incandescent bulbs, except possibly for severe-duty applications in temperature extremes (CFLs may not work in sub-zero temps). I’ve replaced all bulbs other than my decorative and severe-duty fixtures with CFLs, and am super-pleased with the daylight 5000k color I opted for on most of them. That, and there’s nothing like lighting a whole room for the price of just two or three of the old bulbs. :)