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Joel Young
Joel Young

I keep hearing about CFL and LED. What’s the difference between these types of light technology and the classic incandescent bulb? Which is the best?

June 23, 2009

cflbulb.jpg

Of course, in today’s world, we are all being encouraged to discard those ancient incandescent bulbs for the new compact fluorescent lamps (CFL) and light emitting diodes (LED), which for most of us seem really expensive to buy.  I admit that I never really liked the traditional tube fluorescent lights, probably because first, I always have trouble getting the bulbs in - it seems that I always have them out of alignment and second, I usually buy cheap lights that have ballasts that go bad.   But I must admit, now that I’ve started using the screw in CFLs (like the one pictured), I’ve had quite a change of heart.    I’ve yet to take the plunge into the world of LEDs however, primarily because I haven’t yet been able to justify the expense.  And for me, they always seem to look blue. Nonetheless, I know that someday I will make the switch as they all will become clear with the obligatory advancement of technology.Recently I set out to compare our friends, the CFL and the classic incandescent.  The following two tables illustrate the characteristics for a range of incandescent bulbs from 25 watts to 200 watts and a range of CFLs from 5 to 40 watts.    Assuming you turned on each light and left it on for a full year, how much would it cost, including bulb replacement and electricity?

Incandescent (5,000 hour life)

Watts

Lumens

Lm/Watt

Cost

Cost/yr

$/Lm-yr

25

150

6.00

$0.55

$23.96

$0.1597

40

280

7.00

$0.55

$37.76

$0.1348

60

520

8.67

$0.55

$56.15

$0.1080

75

700

9.33

$0.55

$69.95

$0.0999

100

950

9.50

$0.55

$92.94

$0.0978

150

1750

11.67

$1.75

$141.04

$0.0806

200

2400

12.00

$2.40

$188.16

$0.0784

 

CFL (10,000 hour life)

Watts

Lumens

Lm/Watt

Cost

Cost/yr

$/Lm-yr

5

300

60.00

$3.00

$7.23

$0.0241

10

600

60.00

$3.00

$11.83

$0.0197

15

900

60.00

$3.50

$16.86

$0.0187

20

1350

67.50

$4.00

$21.90

$0.0162

25

1800

72.00

$4.50

$26.94

$0.0150

30

2000

66.67

$5.00

$31.97

$0.0160

40

2700

67.50

$9.00

$44.68

$0.0165

As you can see, the lumens per watt increases as wattage increases for both types of bulbs.  In addition, notice that the lumens per watt or luminous efficacy value is 6 to 8 times greater for CFLs than their incandescent brethren and they last twice as long.    As such, even though a CFL costs 5 to 6 times more than an incandescent bulb in the store,  the loaded cost per year of a CFL is still about 20% of an equivalent incandescent.

Of course that looks good on paper (or on a screen), but what does it mean in real life?    In 2008 my house had about 90 incandescent lights totaling 6750 watts.  At a 6% duty cycle, I used a total of 3,544 kWh on lights at a cost of about $373 (don’t ask me how I know this - just accept the fact that we engineers like data).  Anyway, these 6,750 watts put out about 61,875 lumens.   Using the equivalent light in CFLs, I figure I would need only about 955 watts of CFLs to get the same light.   At the same duty cycle this would be only 501 kWh at a cost of $53 - an annual savings of $320.  Note that replacing all 90 bulbs at $3 each would cost only $270.   I think I had better get started.

Posted by Joel Young on June 23, 2009 | Comments (14)

October 29, 2009
In response to: I keep hearing about CFL and LED. What’s the difference between these types of light technology and the classic incandescent bulb? Which is the best?
robots42 commented:

One thing these calculations overlook is that generally we heat our houses, especially at the times we have the lights on, and if we don't heat them with incandescent bulbs we have to use other means so the indicated savings are actually meaningless and wilfully misleading.


September 8, 2009
In response to: I keep hearing about CFL and LED. What’s the difference between these types of light technology and the classic incandescent bulb? Which is the best?
JC commented:

I found a site that backs up the information on this site and also gives an actual comparison between CFL lights and LED lights. Here is the site: ezdiyelectricity.com/?p=519


August 11, 2009
In response to: I keep hearing about CFL and LED. What’s the difference between these types of light technology and the classic incandescent bulb? Which is the best?
TD commented:

Follow-up: I bought a Sylvania 3W led MR16 bulb (12V) at a Menard's store, last week. Impressive amount of light, much better than the PAR20 with 3 leds. The bulb cost $16. Very useful for task lighting and pinspot on artwork, etc. Businesses such as restaurants and galleries (where lighting use is abundant and constant) could benefit greatly greatly with reduced energy cost. CAVEAT: use magnetic transformers, not electronic.


July 29, 2009
In response to: I keep hearing about CFL and LED. What’s the difference between these types of light technology and the classic incandescent bulb? Which is the best?
GuyWhoReads commented:

I have not had as much luck with the CFLs. Even trying to buy the same brand, I find inconsistencies in how long they last. What replacement rate was assumed in the above cost analysis and how was it derived (hopefully not just based on the labels' brags of 7 year life - I have yet to see that).


July 29, 2009
In response to: I keep hearing about CFL and LED. What’s the difference between these types of light technology and the classic incandescent bulb? Which is the best?
MD commented:

One issue that we have is the disposal of the CFL after it fails. My understanding is CFL's contain trace ammounts of metals (mercury,etc) making them hazardous to dispose of in normal trash. There are limited ways for the common public to dispose of CFL's in a safe manner. It would be easier for me to accept the CFL if there was a simple and easily available method to dispose of them so I don't feel i'm harming the environment. When I ask others how they dispose of CFL's, the answer is always "I just throw them in the trash". There needs to be a common infrastructure across the country for disposing of and reclaiming the materials inside the CFL bulbs.


July 29, 2009
In response to: I keep hearing about CFL and LED. What’s the difference between these types of light technology and the classic incandescent bulb? Which is the best?
Ed commented:

As commented, LED's will have as good or better efficiencies as CFL's but with lifetimes of 2X and more. However, the major advantages are there is better durability (shock or shatter resistant), they have instant on capability (don't have to wait for them to get to full intensity), and they aren't as much of a hazard because they lack the mercury of CFL's. The disadvantages are the cost (3 to 10x), which should come down in time, and the availability right now (still don't see too many std bulb equivalents although they are coming on big time with Christmas type lights).


July 28, 2009
In response to: I keep hearing about CFL and LED. What’s the difference between these types of light technology and the classic incandescent bulb? Which is the best?
mnc commented:

I have replaced my most frequently used bulbs with CFL. The major difficulty is the delay in coming up to full brightness. One room in our home is so dark that I needed to put back half of the incandescents in order to have a comfortable light level while the CFL bulbs warm up.


July 28, 2009
In response to: I keep hearing about CFL and LED. What’s the difference between these types of light technology and the classic incandescent bulb? Which is the best?
Jacob commented:

the title is misleading. You don't compare LEDs vs. CFL, you compare CFL vs conventional incandescents. Thanks for wasting my time with a misleading title.


July 28, 2009
In response to: I keep hearing about CFL and LED. What’s the difference between these types of light technology and the classic incandescent bulb? Which is the best?
Karim commented:

Can somebody also share there knowledge on the even density of lighting and the ease of control specially in area where this is critical?
Thank you,


July 28, 2009
In response to: I keep hearing about CFL and LED. What’s the difference between these types of light technology and the classic incandescent bulb? Which is the best?
Tom W commented:

The power savings in changing the bulbs is significant. If you live in an area where it is hot, remember all that waste heat must be removed. Also consider savings in your air conditioner electric bill.


July 22, 2009
In response to: I keep hearing about CFL and LED. What’s the difference between these types of light technology and the classic incandescent bulb? Which is the best?
TD commented:

A brand-name 120Lm LED bulb costs ~$30usd at a home-improvement store. It has similar Lm/W efficiency as a CFL (3W). It cost 10X the cost of a similar output CFL, but should last 2X longer. Next year, lifetime cost should be closer to CFL, if prices drop like CFL prices have.


July 10, 2009
In response to: I keep hearing about CFL and LED. What’s the difference between these types of light technology and the classic incandescent bulb? Which is the best?
Chris commented:

Very nice straight forward comparison; I would love to see LED's compared as well (maybe I just need to read a few more blog entries to get to the comparison). I know the color temp on the new CFL’s and LED’s is much higher than traditional bulbs… how does this translate to actual radiated heat?
In a new addition on our house we have found that we actually can heat the addition just with the use of the computer equipment and the lights in the room. This is in a newly built addition on our house in Northern New England. Of course in the summer we have to pay to cool the room from all those heat sources…


July 2, 2009
In response to: I keep hearing about CFL and LED. What’s the difference between these types of light technology and the classic incandescent bulb? Which is the best?
Joel Young commented:

The average for my electric bills in 2008 was $0.105


July 1, 2009
In response to: I keep hearing about CFL and LED. What’s the difference between these types of light technology and the classic incandescent bulb? Which is the best?
Ron commented:

Very good analysis. Whats the unit cost of a Kwh in your area?

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