CFL's, Wattage Equivalents

[jmellc]

If this has been posted before, please guide me to the right page.

I have seen 1 or 2 CFL's lamps labeled with their wattage & what incandescent bulb it was equal to.

Is there a chart anywhere to reference for all CFL's? Most lights are still marked for incandescent bulb wattages, as far as I can tell, unless the are specifically CFL fixtures.

Thanks for any help.

 

[Dennis Alwon]

In general divide your incandescent wattage by 4. Thus a 100 watt bulb is equivalent to a 25 watt CFL--approximately.

 

[sgunsel]

That seems to be the manufacturers' thinking. It works well for the small 13 watt lamps that seem to be equivalent to a 60 watt incandescent. But I have not seen a 24 watt CFL that looks like a 100 watt equivalent based on visual appearance. It doesn't seem to scale very well.

 

[Dennis Alwon]

That seems to be the manufacturers' thinking. It works well for the small 13 watt lamps that seem to be equivalent to a 60 watt incandescent. But I have not seen a 24 watt CFL that looks like a 100 watt equivalent based on visual appearance. It doesn't seem to scale very well.

What do you mean by "look like"-- we are talking lumens here.

 

[broadgage]

There is no exact equivalent since both incandescents and CFLs vary a bit.
However the guide above is a fair average, multiply the CFL wattage by 4 to get an approximate incandescent equivalent.

Relatively small changes in voltage (well within normal tolerances) have a significant influence on incandescent output.
Quite a bit more at 125 volts than at 110 volts.
CFLs are less influenced by voltage but tend to be sensitive to temperature variations.

 

[G._S._Ohm]

Perceived brightness vs. actual brightness.

You could illuminate a white sheet of paper 3' away from each light and read the intensity on the paper by using a camera as a light meter. Using the formula for Exposure Value gives you the intensity.

For perceived intensity you can have two sheets of paper at varying distances from the lights until you judge the paper brightness to be equal, then use the formula for light intensity change with distance.
Try searching "flicker photometer."

If you do these experiments, please post your results. Almost certainly the manufacturers have overstated the intensity ratios.

Also the color temperature for each technology is different and the eye responds to different light wavelengths differently.

Along with Mr. Gage's comments, 125 v vs. 110 v should give (125/110)^3.5 = 1.6x brighter. Wikipedia has an article on comparing different kinds of lamp technology.

 

[gar]

110125-1223 EST

A number of good comments above.

About 2 years ago I ran some comparison tests using a cadmium sulfide photocell for intensity measurement. The spectral response of CdS is supposed to be somewhat similar to the human eye.

I have plots of these on my website at
http://beta-a2.com/EE-photos.html
See photos P9 thru P18. All normalized curves are using a 75 W incandescent as the reference. This reference being photo P9. Note: the "power" plot is actual watts. The "power normalized" plot is referenced to the 75 W bulb. The "power normalized" curve is use to show the relative (percentage) variation with voltage.

My results seem to imply a ratio of 3 to 1 instead of 4 to 1.

.

 

[Besoeker]

That seems to be the manufacturers' thinking. It works well for the small 13 watt lamps that seem to be equivalent to a 60 watt incandescent. But I have not seen a 24 watt CFL that looks like a 100 watt equivalent based on visual appearance. It doesn't seem to scale very well.

Sometimes CFLs get a bad rap because they take a while to reach full brightness. At initial switch on, they can look much dimmer than the equivalent incandescent. And we are used to the instant light from an incandescent, that may go some way to explaining the difference in perception.

 

[sgunsel]

By "looks like" I meant that I placed a 24 watt CFL that the manufacturer alleges to be equivalent to a 100 watt incandescent lamp in the same fixture and the observed brightness in the illuminated area was noticeably less. I did not measure the lumens or intensity, but I could read comfortably with one and not the other. And this was repeated on more than one occasion. Similarly, when replacing 60 watt incandescents with 13 watt CFLs, the output consistently appears to be very similar, even if the color is not an exact match. Not scientific perhaps, but what really matters.

 

[gar]

110125-21812 EST

Just now did a light comparison of a 13 W GE FLE 13HT3/2/SW with a 60 W 120 V and a 25 W 120 incandescent. These measurements were at a distance 5 ft from the lamp, as were my measurements 2 years ago, and viewing side illumination. This means the photocell is 90 deg to the axis of the bulb in the long direction.

The photocell resistance measurements were:

25 W 1280 ohms
60 W 533 ohms

13 W 815 ohms

Light intensity of an incandescent is proportional to power input for the same color temperature. The photocell resistance is inversely proportional to light intensity over many decades.

60/25 = 2.4
1280/533 = 2.402 good correlation.

1280/815 = 1.57
1.57 * 25 = 39 W

From this I would classify the 13 W CFL as approximately comparable to a standard 40 W incandescent. Thus, incandescent to CFL ratio is about 3 to 1.

.

 

[Electric-Light]

First, you'll have to assume stated lumen is correct, but this isn't always so.

The wattage equivalent is usually written in a way that makes the product looks most favorable. For example, a 60W equivalent for G25 bulb doesn't have to produce as much output as A19 equivalent, because decora lamps are usually less efficacious.

Also, one 100W lamp produces more output than three 40W lamps, again because of difference in efficacies.

The PAR and R CFLs that have become more common recently can mislead significantly. A 26W PAR38 may claim the same lumen output as the 26W spiral lamp it is based on.

The base 26W lamp maybe comparable with an A19 "regular 100W light bulb" but the efficiency of PAR optics isn't quite the same with a smaller halogen capsule compared to a huge spiral tube, so the "out the bottom" lumens can be significantly less.

 

[sgunsel]

GAR, that is very interesting. What temperature CFL was used? I find the daylight (4100K) to look brightest and with the best color (whitest?), both in CFL and T8 lamps. Maybe the phosphors are more efficient or maybe we just see better because of the wavelengths produced.

Our eyes do not respond equally to different wavelengths of light. I replaced a high pressure sodium lamp in my back yard with an identical wattage metal halide and the difference was stark. Although their output in lumens is allegedly similar, the yard looks much brighter with the metal halide, even though your test might indicate the sodium light was "brighter". The sodium light is monochromatic and has very poor color rendition, but might well show a higher output with a CdS sensor. If you look at an infra red or ultraviolet source, you could get very high brightness, but the light produced is invisible to our eyes.

You measured the brightness emanating from a point on the lamp. If extended in all directions around the lamp in three dimensions, all measurements surely would not be equal. If all of those measurements would be integrated, you could determine the relative light output for the lamp. But that does not address the effects of differing wavelengths (color).

Maybe I wasn't clear earlier. I have found that replacing a 60 watt incandescent with a 4100K 13/14 watt CFL in most fixtures in my house are roughly equivalent in apparent lighting. Replacing a 100 wattt incandescent with a 24 watt CFL is clearly not. This is only my perception. The CdS cell readings would surely differ.

 

[gar]

110126-0912 EST

sgunsel:

http://genet.gelighting.com/LightPr...ps_Compact+Fluorescent_Self-Ballasted_Spiral®

FLE 13HT3/2/SW is apparently --- Warm White 2700 K

My measurements are not a total integration of light emitted from the lamp, but a side view at a reasonable distance, 5 ft. But I use the same test conditions for any lamp I test. A comparison with a straight tube fluorescent presents other problems in evaluation for comparison purposes.

I expect a cool white, 4100K, to be brighter, but that is a much different color temperature and spectral distribution compared to a standard incandescent.

Interesting site:
http://www.fullspectrumsolutions.com/whats_wrong_with_cool_white_lamps.shtml
But fails to really define what is a full-spectrum fluorescent's spectrum.

I will see if I can find a cool white CFL for comparison.

.

 

[G._S._Ohm]

By "looks like" I meant that I placed a 24 watt CFL that the manufacturer alleges to be equivalent to a 100 watt incandescent lamp in the same fixture and the observed brightness in the illuminated area was noticeably less. I did not measure the lumens or intensity, but I could read comfortably with one and not the other. And this was repeated on more than one occasion. Similarly, when replacing 60 watt incandescents with 13 watt CFLs, the output consistently appears to be very similar, even if the color is not an exact match. Not scientific perhaps, but what really matters.

Actually, with "point sources" of light like bulbs are, all you need is a tape measure.

If a 60 W incand. bulb at 5' makes a piece of paper as bright as a CFL at 3', then the CFL "equivalent" wattage is 60 W x (3'/5')^2 = 22 W.

 

[Electric-Light]

Our eyes do not respond equally to different wavelengths of light. I replaced a high pressure sodium lamp in my back yard with an identical wattage metal halide and the difference was stark. Although their output in lumens is allegedly similar, the yard looks much brighter with the metal halide, even though your test might indicate the sodium light was "brighter". The sodium light is monochromatic and has very poor color rendition, but might well show a higher output with a CdS sensor. If you look at an infra red or ultraviolet source, you could get very high brightness, but the light produced is invisible to our eyes.

Sodium is not monochromatic, unless you're talking about LPS SOX, which is not something you find normally. Uncorrected CdS sensor is pretty much useless for quantifying visible light. [/quote]
If you were measuring output in radiometric output (watts for output and brightness in mW/m^2) then you're correct.

Radiometric measurements are used for UV and IR sources, but they're not used for general lighting. Photometric measures are used instead, which means they're weighed to human eyes. Lumen is a unit weighed to human eye response and well made light meters respond to best approximation of human eye sensitivity curve.

You measured the brightness emanating from a point on the lamp. If extended in all directions around the lamp in three dimensions, all measurements surely would not be equal. If all of those measurements would be integrated, you could determine the relative light output for the lamp. But that does not address the effects of differing wavelengths (color).
Maybe I wasn't clear earlier. I have found that replacing a 60 watt incandescent with a 4100K 13/14 watt CFL in most fixtures in my house are roughly equivalent in apparent lighting. Replacing a 100 wattt incandescent with a 24 watt CFL is clearly not. This is only my perception. The CdS cell readings would surely differ.

Of course CdS will differ, because uncorrected CdS is horrible at emulating human eye response. High accuracy light meters are expensive. Gossen Mavolux is like $1,800, a CdS cell is like 25 cents a piece.

Interesting site:
http://www.fullspectrumsolutions.com/whats_wrong_with_cool_white_lamps.shtml
But fails to really define what is a full-spectrum fluorescent's spectrum.

That's the company that raised hell over "made in the USA" over Everlast. That company is full of crap. They're the one who offers 3300 lumen 32W 91 CRI T8 lamp, something that even top brand names can't make.

That website has a link to some lab test for some of their products, but that lab doesn't appear to be referenced anywhere else. When I asked for verifiable lab result, this is what they tell me
"Because we have a patented proprietary blend, I am not sure how much information I can release to you"

Patented means that the protected art is published, in exchange for legally protected right. These guys won't even cough up the US patent # of the supposedly "patented" technology.

 

[tom baker]

Best way to compare is with lumens. Also look at the lumens per watt. The new lighting facts label from the DOE is make this much easier, it has 6 key metrics.
Take a look here:
http://www.lightingfacts.com/default.aspx?cp=content/label

Think lumens, not watts. We electricians have always used watts and its time to get away from that esp as we move into LEDs

Tom

 

[ActionDave]

I find the lumens put out by LED's to be very unsatisfactory based on the street lights changed to LED from MH in my hometown.

 

[ptonsparky]

Best way to compare is with lumens. Also look at the lumens per watt. The new lighting facts label from the DOE is make this much easier, it has 6 key metrics.
Take a look here:
http://www.lightingfacts.com/default.aspx?cp=content/label

Think lumens, not watts. We electricians have always used watts and its time to get away from that esp as we move into LEDs

Tom

Link doesn't work for me.

I am trying to find a 500 watt inc to CFL replacement. Anyone with a catalog #?

School gym that is still using 28 of them. Gym is warm anyway.

 

[Electric-Light]

110126-0912 EST

sgunsel:

http://genet.gelighting.com/LightPr...ps_Compact+Fluorescent_Self-Ballasted_Spiral®

FLE 13HT3/2/SW is apparently --- Warm White 2700 K

My measurements are not a total integration of light emitted from the lamp, but a side view at a reasonable distance, 5 ft. But I use the same test conditions for any lamp I test. A comparison with a straight tube fluorescent presents other problems in evaluation for comparison purposes.

I expect a cool white, 4100K, to be brighter, but that is a much different color temperature and spectral distribution compared to a standard incandescent.

Interesting site:
http://www.fullspectrumsolutions.com/whats_wrong_with_cool_white_lamps.shtml
But fails to really define what is a full-spectrum fluorescent's spectrum.

I will see if I can find a cool white CFL for comparison.

.

Link doesn't work for me.

I am trying to find a 500 watt inc to CFL replacement. Anyone with a catalog #?

School gym that is still using 28 of them. Gym is warm anyway.

Well, a 500W incandescent lamp is about 10,000 lumens.

No such thing as 10,000 lumen screw-in CFL in common market. You think you can go with 14 x 4x F54T5/HO conversion? F54T5/HOs are 5,000 lumens.

Another option is 14 x 6 lamp (or 28 x 3 lamp) x F32T8/RE80/HE on 1.2 BF ballast. GE makes 6 lamp @ 1.18 (21,240 mean lumens using premium RE80 lamps) using 221W or ~95 system lumens per watt. 3100W for 14 x 6 setup vs 14,000W for current setup.

It will be costlier, but you'll have 78% reduction in energy use with no reduction in output. You'll never get this much gain with a spiral screw in CFL anyways.

Given the longer length of fixtures, I think you can get away with one creative placement using half as many. It's cheaper to go with 14 fixtures than 28.

 

[G._S._Ohm]

Uniformity of the light intensity on the illuminated surface is another consideration.

If you really want to get into this, Lighting Handbooks like you find at Border's or Barnes & Noble's are about 4" thick.
In this respect, Lithonia was very helpful. By e-mail they will supply you with a computer generated intensity plot for their fluorescent troffers. Once you know this you can, in principle, work backwards to how many of what kind of lights you need.