Fluorescent vs Incandescent lights


Glen Turner writes about silly people who think that fluorescent lights don’t save energy over their lifetime [1].

A compact fluorescent light (one that is designed for the same socket as an incandescent globe) is not the most efficient light source, the Luminous Efficiency page on Wikipedia [2] lists a CFL as having an efficiency of between 6.6% and 8.8% while fluorescent tubes can be up to 15.2% efficient and low pressure sodium lamps are 27% efficient! But given that low pressure sodium lights are unsuitable for most uses due to being monochromatic and having a long warm-up time and the fact that fluorescent tubes are often not suitable due to design an 8.8% efficiency is pretty good. LEDs can give up to 10.2% (and prototypes offer 22%) but don’t seem to be available in a convenient and reliable manner (they are expensive and the ones I’ve tried have been unreliable).

When comparing fluorescent with incandescent one factor to consider is the power used. While high-temperature incandescent lights are quoted as having 5.1% efficiency and a 100W 110V tungsten incandescent globe is quoted as having 2.6% efficiency a 40W 110V globe will only have 1.9%. If you want to save energy then you probably don’t want to use 100W globes, using less light is the first way of saving energy on lighting! So the efficiency of incandescent lights used for the comparison should probably be closer to 1.9% than 2.6%.

Now the theoretical performance won’t always match what you get when you buy globes. There is some variation of quality between manufacturers and there are at least two distinct “colours” of fluorescent lights (one is about 5800K – similar to our sun, the other is something over 8000K – blue-white), I expect some difference in efficiency between lights of different colour range.

I see CFL lights marketed as being 5 times more efficient than incandescent lights, my observation is that they appear to be about 4 times more efficient (IE I replace a 40W incandescent with a 10W CFL or a 60W incandescent with a 14W CFL). Glen claims that an 8W CFL can replace a 60W incandescent globe, the only possibility of getting a factor of 7 or more efficiency improvement (according to the data on the Wikipedia page) would be to replace some 5W incandescent globes with CFL. In my experience (converting two houses that I lived in to CFL and the conversions of some friends) such an efficiency benefit is not possible on direct electricity use.

However in a hot climate any waste heat needs to be removed with an air-conditioner. So when a 60W incandescent light is replaced by a 14W CFL there is 46W of waste heat removed, with an ideal efficiency of a heat-pump it would take 15W to remove that heat from a building (and possibly more if it’s a large building). So in summer we are not comparing 60W to 14W, it’s more like 75W to 14W.

The issue of economics that Glen raises is more complex than it seems because governments often give companies significant discounts on electricity costs, EG in Australia aluminium refineries are subsidies heavily so they pay much less than home users. So hypothetically it could be possible to manufacture a device made entirely of aluminium which saves electricity (and therefore money for the user) but not enough to cover the electricity used in aluminium refining. However when we consider the margins of the various middle-men it seems quite unlikely that such a hypothetical situation could actually happen.

As for the issue of mercury in fluorescent lights there are two things to consider. One is that it is possible to recycle mercury (in Australia at least), the other is that coal fired power plants have a lot of mercury in their smoke…

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23 thoughts on “Fluorescent vs Incandescent lights”

  1. Anonymous says:

    If incandescent bulbs had not changed in the past decade or two, I’d gladly switch to CFLs. However, several brands of incandescent bulbs started introducing variants with more “natural” light. We switched our entire house over to GE’s “Reveal” bulbs; I’ve also seen a few good recommendations for Sylvania’s “Daylight” bulbs. We’ve tried various kinds of CFLs, and none of them put out light of sufficient quality to compete with these. Until they do, we won’t switch.

  2. Anonymous says:

    (Hmmm. I just noticed that Sylvania offers a Daylight CFL; I haven’t seen that in the store before. I may give that a try.)

  3. Borislav Trifonov says:

    There’s a serious problem with all CFL lights and that is that they have a spiky spectrum that can’t match sunlight–even if you filter it. On the other hand, incandescent lights have a smooth spectrum that can be matched to sunlight when you filter it (see high end incandescents such as Solux). Two lights can be matched to the same color temperature and white points while still having different spectra (this is because these are summary numbers and don’t tell you that much about the actual distribution w.r.t. wavelength). So you could have two equally “white” lights that each make colored objects appear different than the other. And only incandescents can have the spectrum matched to sunlight–that means you’re losing out on color reproduction compared to natural light if you use CFLs or other lights. Considering that studies have shown correlation between natural light and productivity and health (I can give references), I’d tell anyone considering switching to CFLs to think again.

  4. etbe says:

    Borislav: Please cite references.

    I expect that the correlation between pollution free air and health is considerably stronger than the correlation between natural light and health.

  5. Borislav Trifonov says:


    I quote:
    “Using multivariate linear regression analysis, the study examined 21,000 school records from 3 school districts in 3 states and daylighting conditions in over 2,000 classrooms. Data indicate students with the most classroom daylighting progressed 20 percent faster on math tests and 26 percent on reading tests in one year than those with the least. Similarly, students with the largest windows progressed 15 percent faster in math and 23 percent faster in reading than those with the least.”
    That’s just for the productivity.
    For health, just consider the references cited at en.wikipedia.org/wiki/Light_therapy and the notes about studies where artifical light wasn’t as beneficial (since photons are photons are photons, the only difference between daylight and a given light source is the spectrum–thus to reproduce sunlight you just need to match its spectrum).

    ebte, you forget that carbon dioxide is not pollution–it’s a greenhouse gas, but even if you double CO2 concentration in the air, that has no direct impact on health due to the increased CO2 getting in your lungs; it’s not toxic, and is therefore NOT pollution.
    The only serious pollution one gets for electricity generation is burning coal, but that just says coal is a polluting energy source, not that using more electricity necessarily causes pollution!

    There’s also a detailed discussion on other CFL problems by an electrical engineer I respect here: sound.westhost.com/articles/incandescent.htm

    I haven’t even started talking about the radio-interference from the CFL power supplies polluting the spectrum and interfering with anyone trying to listen to shortwave radio, as well as ham radio services, but I realize that’s a problem for a niche, so I won’t go into it.

    The point is that in terms of energy efficiency, what we should be doing is finding more clean energy rather than taking away from technological progress and comfort/convenience–increased efficiency is never free and forces a compromise.

    P.S. I live in Vancouver and it’s cloudy and sunless for at least six months of the year here, so proper light is all the more important here. Add to that that nine months of the year the house is being heated, so any ‘waste’ from indoor appliances is used up and thus they are all 100% efficient.

    I’ve had this whole argument already on another forum, when I was startled to hear that the Canadian government decided to ban incandescent bulbs… insanity–if people should choose they want to save energy, that’s fine, but it’s not the place of a nanny state to force people to do so. http://www.head-fi.org/forums/f11/incandescent-bulb-ban-233906

  6. etbe says:

    Borislav: That’s a good reference to support the claim that sunlight is better than artificial light. But it doesn’t seem to support the claim that incandescent light is better than fluorescent light (if I missed something please cite the page number).

    The next issue is how the efficiency and price of Full Spectrum fluorescent lights (as described in the above page) compares to regular fluorescent lights.

    Both coal and nuclear power are polluting energy sources. Once we replace all coal and nuclear power plants with renewable energy then we can look at other health measures related to energy use.

    The westhost.com article is very partisan in favor of incandescent. For example it cites the heat problems of enclosed light fittings for CFLs but doesn’t note the fire risk of halogen down-lights and incandescent lights in sealed fittings.

    I agree that getting clean energy is the best thing to do. It’s a pity that the coal, oil, and nuclear industries are so effective at preventing that. I also agree that “waste heat” is not a problem in winter. I use my old incandescent globes in winter.

    Also I think that taxing products you want to deprecate rather than banning them is the best thing to do.

  7. Aborted says:

    The difference between the lights insists on the variance in color. It will also deploy electromagnet charges to determine the 200MPA that will eventually mount to a glass chamber which in turn decreases voltage.

  8. Borislav Trifonov says:

    etbe, it was addressed in my first post here: an incandescent has a continuous spectrum, which means that in practice it can be filtered to match sunlight _exactly_. You cannot do this with the spiky spectrum of a CFL because there are no sufficiently narrowband filters in existence (and also since most energy is concentrated in the spikes, you’d be losing way more efficiency).

  9. etbe says:

    Borislav: The difference between sunlight and artificial light is not limited to the spectrum. Sunlight comes from a single source in the sky, it varies in intensity through the course of the day.

    I believe that fluorescent lights can be constructed with a range of different compounds used in the fluorescent paint to give a range of light frequencies. The question is how much of a range is really required. I find it difficult to believe that exactly matching the frequency range of the sun is necessary for health – if there was I’m sure that someone would have determined the optimum latitude for healthy living by now.

  10. Borislav Trifonov says:

    This isn’t just about matching exactly, it’s not even close. The spectrum of a fluorescent is a polar opposite of the smooth spectrum of natural light. Typical fluorescent: http://commons.wikimedia.org/wiki/Image:Fluorescent_lighting_spectrum_peaks_labelled.gif
    Also note that your hypothesis that source location does not fit in with the productivity study I mentioned, since that’s dealing with light coming in from windows which bias the direction, then reflected diffusely around by walls, etc. Moreover, even outdoors all the irradiance does not come directly from the sun, since a very large portion of light is scattered and comes from all directions of the hemisphere of the sky (the sky is much dimmer than the sun’s apparent disk, but it also has an enormous half-angle in comparison). Direction of the light is basically a non-issue.

  11. Borislav Trifonov says:

    Er, I meant solid angle, not half angle… that’ll teach me to post before my morning coffee -.-

  12. someone says:

    Anyone who doesn’t switch to cfl’s are irresponsible retards.

  13. Borislav Trifonov says:

    To all thread readers it’s quite clear:
    “someone” is the only retard here!

  14. etbe says:

    Borislav: While not phrased well, someone does have a point about the irresponsibility of using excess energy while climate change is such a threat to our way of life. Everyone who lives near the sea (the majority of the world’s population and the population of most capital cities of countries that are more than 200 years old) has the risk of having their home becoming below sea level within one lifetime. Coal fired power plants are a major cause of the climate problems that we currently experience.

  15. Borislav Trifonov says:

    1. I’ve presented a clear arguments as to why CFL light quality is inadequate.

    2. Why waste coal for energy? Your suggestion that it’s either burn coal, or compromise quality by enforcing efficiency, is a false dichotomy! Coal should be saved for plastics manufacture and the chemical and fertilizer industries–with peak oil looming, it’ll be sorely needed (current fall of oil prices is only temporary and due to demand destruction resulting from the current economic trouble).
    With breeder reactors and the use of thorium as fuel in addition to uranium, nuclear energy can meet increasing demand for a couple of centuries. Breeder reactors reduce the waste amount significantly; the only opposition is political and there is no technical disadvantage. The leftover waste can be further processed by the CERN Waste Transmuter type devices which results in significantly reduced radioactivity. Finally, after vitrification storage is failsafe as it cannot leach into air/water/etc. The reduced amount of waste by using breeders makes vitrification practical.
    No currently practical clean source of energy can get provide the amount of energy nuclear can within an order of magnitude. You’d have to cover the planet with energy-intensive-to-produce solar panels and bird&bat-killing noisy wind turbines.
    By the time nuclear fuel runs out, either humans would be extinct by war/disease/etc., or space-based solar and fusion would have taken over (though ITER will be operational in about a decade and then it will take a couple more to build commercial reactors–by saying 200 years I’m giving the estimate a 500% error margin).

  16. etbe says:

    Borislav: Nuclear power is irrelevant to the current problems. It takes so long to construct nuclear power plants that the climate changes issues will be decided before nuclear power can make a difference. Reducing power use (which can be done immediately) and building power plants that use renewable energy sources (such as solar and wind) is the way to go.

    There is no evidence of wind turbines being a great hazard to birds and bats. It’s amusing that the coal industry keeps pulling out this one when no-one has ever objected to building a skyscraper on such grounds!

    For example if 2% of farmland in Victoria (one of the more populous states in Australia) was used for wind turbines then all the electricity for Victoria would be supplied. Note that the farmland in question could still be used for farming, cows don’t mind if there are turbines overhead and wheat cares even less.

  17. Borislav Trifonov says:

    > the climate changes issues will be decided before nuclear power can make a difference”

    Who says?

    > There is no evidence of wind turbines being a great hazard to birds and bats.


    > It’s amusing that the coal industry keeps pulling out this one

    The article above references University of Calgary researchers, not coal industry representatives (and on top, CBC is a seriously left-wing station)

  18. etbe says:

    Borislav: The comments of the article you cited point out that the turbines in question were not ideally placed (they did not take bat movement into account when planning) and also the fact that stopping the turbines at low wind speeds (which produce little electricity) will save the bats (who like to fly when it’s not too windy).

    Also the above URL has an article which refutes most of the FUD about windmills and birds.

    As for how soon the issue gets decided, please read some recent news reports about ice melting around the north pole. Wind farms can be completely built and installed (including an environmental assessment) in 18 months. Nuclear power plants take 10 years or more.

  19. Jenni says:

    I find the whole argument of incandescent vs CFL to be quite ridiculous. Does anyone actually realise how must their lighting contributes to the elec bills? Energy retailers charge usage by the Kwh. It takes 10 hrs using a 100watt globe to use 1Kwh of power. Energy providers charge by the Kwh. If your energy providers charges 18c per Kwh then that is what it costs to run your 100watt globe for 10 hrs. Lighting is usually the smallest part of a household elec bill. CFLs are supposed to have a long life but my experience with them has been that they last as long as the average incandescent. A 10,000hr incandescent is about half the cost of 10,000hrs CFL while a lower hr rated incandescant is cheaper again. Households need to factor in the cost of the globe and the cents that they will save compared to using a CFL. Green house gas emmissions are also comparably small. Lights turn on, lights turn off. It’s appliances like refrigration and heating/cooling that usually use the most power in a household and therefore produce the most green house gases. Safe mercury disposal is also another issue. Thanks to the democratic dictatorship that I live in for taking away my freedom of choice when it comes to choosing what sort of light bulb I can buy. How petty! Does government tell big business with highrise buildings that they have to turn all their lights off? How much energy would that save each night? Does anyone talk about the effects of heat radiation when it comes to global warming? The more surfaces you have like concrete, steel and brick buildings the more heat is absorbed during the day and re-radiated at night. How does that not contribute to global warming? Bigger population, more buildings. More heat-traps. Greater use of appliances such as air cond because homes are not being built to be climate friendly (verandahs, vents in roofs to let hot air escape, correct window treatments etc).

  20. etbe says:

    Jenni: This time last year my household electricity use (including CFL lighting) was an average of 13KWh per day. That included a minimum of one room being lit for 16 hours a day. If a 14W CFL was replaced with a 75W incandescent light then that’s almost 1KWh per day already. As it’s common to have two or three lights on at one time (especially during the evening and on overcast days) the savings for my usage pattern could be as high as 3KWh per day. That means that if I used incandescent lights my electricity bill could increase by up to 25% before counting the extra electricity used by the air-conditioner to remove the waste heat.

    If you have evidence of CFLs not lasting as long as they are advertised then please take appropriate action against the companies that make false advertising claims. If you don’t have evidence then please don’t spread FUD.

    If you had read my post you would have noticed that it’s possible to recycle objects that contain mercury in Australia and that smoke from coal fired power plants contains mercury.

    The electricity companies will routinely turn power off to sections of the grid when there is too much load. Yesterday the Crown casino and the surrounding area was cut off. Maybe if more people used CFLs and decreased their direct and indirect (through A/C) electricity use then the power outages wouldn’t have needed to be as big or as long. Your claim about the government not telling companies when to turn off their building lights is bogus.

    Regarding your comment about heat radiation and global warming, please study some science before commenting on such things. A level of scientific knowledge equivalent to that which is taught at year 11 would do.

  21. Jenni says:

    Thanks for the contempt! I never claimed to be a scientist. I want to point out that there are appliances whose usage produces much higher levels of green house gases for households than lighting. Again much of this depends on how the appliance is used. I believe that much can be done for home design to minimise the need for excessive cooling and heating. We didn’t have blackouts in the current Vic/SA heat wave because everyone had their lights on!
    You used the scenario of lighting required for 16 hrs a day in one room. This would pay off to use a CFL over the course of a year. Much household lighting would not be used in this manner. The value add depends on how the item is used. You mentioned the extra elec used by air cond to remove the waste heat from incandescent lighting. Depending on where and how you live this may not be an issue.
    Have you seen city buildings lit up at night when they are substantially empty? Looks pretty but at what cost? Ok for the government to tell me (individual but I vote) that I can’t buy an incandescent globe anymore but not okay to tell a company (lobbying power, $$$$?) with an empty building that they cannot have it lit up? You say bogus, I say double standard.
    As for disposal of mercury containing CFLs the Australian Government website states “CFLs can generally be disposed of in regular garbage bins – where the garbage goes to landfill.” It does mention recycling however the depots that will take CFLs will not be readily accessible to all consumers especially those who live in country areas.
    I have read the submission from Peter Bitto of CMA Eco Cycle to Sustainability Victoria on the draft Metropolitan Waste and Resources Recovery Strategic Plan and it contains disturbing figures on the current level of landfill disposal of fluorescent lights and the possible environmental effects of this unregulated dumping.
    CFLs work for you and that’s fine. Let me have my freedom of choice and let me avoid the possible health risks if I accidentally break one.

  22. etbe says:

    Jenni: I have had many people who have little knowledge of science try and convince me that CFLs (and every other change to energy use other than using more coal) is a bad thing. I have little patience for people who just make things up.

    If everyone used only incandescent globes then the blackouts would have covered larger areas. If everyone used only fluorescent lights then the areas would be smaller. If we had smart meters and the ability to have dynamic electricity pricing and turn off non-essential appliances when the price rises then we would have had no blackouts.

    The lighting in empty buildings has been dramatically reduced over recent times. One problem at the moment is that most large buildings have one switch covering 25M^2 or more. If one person is working late (or early) then you might have an entire floor lit for one person because the switches don’t allow anything else. Electricity expenses are a significant factor for corporations, and they are trying to reduce it. I suspect that fear of OH&S issues is more of a cause of needless lighting than a desire to make the building look good. The ideal would probably be to have low power lights covering all walkways and switches for the main lighting on a per desk basis. Then if one person is working on a floor you might have 100W for lighting the walkways and 20W for their desk. Of course as some corporations have dual-core computer systems running 24*7 on every desktop (wasting 100W per system) the lighting might actually be a minor issue. We can of course solve the computer power waste too, but that’s a separate issue.

    Fluorescent lights have been used since the 1940’s, and I believe that they became widely popular in the 1960’s. The older fluorescent tubes had much higher levels of mercury, so even if you choose not to recycle your used fluorescent lights (tubes and CFLs) the amount of mercury in the landfill will be a small fraction of what it used to be (newer fluorescent lights use about 1/10th the amount of mercury and none of the beryllium compounds that were used in 1940).

    One interesting aspect of the mercury hysteria is that AFAIK no-one ever tests a house for mercury or lead before purchase! You claim to be worried about breaking a CFL (with low-mercury design) but you probably wouldn’t know if an entire box of high-mercury fluorescent tubes had been smashed in your house by the previous owner! Also every house that is more than 40 years old will have some lead-based paint and some asbestos used in it’s construction.

    In terms of government action, I generally don’t approve of banning things. It’s better to just change the tax rates and let the market sort it out.

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