... seeking simple answers to complex problems, and in the process, disrupting the status quo in technology, art and neuroscience.

Saturday, December 28, 2013

The Energy Star / CFL Efficiency Myth

If you still want incandescents:


First posted on 02-01-07:

For years the Federal Energy Star program has perpetuated the myth that if you buy appliances (or any electrical device) for the home that uses less energy, you'll see proportional savings in your monthly power bill. This is rarely the case.

Other eco-writers do similar simplistic math to calculate savings in money, energy, and carbon. A recent example is Charles Fishman's September 2006 article in Fast Company magazine about WalMart's CFL project, "How Many Lightbulbs Does it Take to Change the World?".

The claim is made that if a single light bulb using 45 watts less is placed in 100 million homes, 6.57 billion Kilo-Watt-Hours will be saved. The fact is, unless you are cooling your house, there is often ZERO savings. Charles focused on the bulb, but forgot about the home. His entire premise is based on a false assumption. The savings are grossly exaggerated for most homes.

"Wasted" energy takes the form of heat. And this heat helps keep you warm, if only just a small amount. For most of America, for much of the year, that 45 watts will be automatically added back in by the home heating system to maintain the same level of comfort. If the home is heated with electricity, the savings in dollars, energy and carbon production is literally ZERO.

The only time energy is actually saved is when the air conditioning is running or you have the windows open to cool the house. With the air conditioning on, the savings can even be a little greater than 45 watts, but for most of America, that's a small part of the year. What are the savings for the rest of the year?


If you are not cooling your home, EVERY light bulb and appliance is 100% efficient.

Here's why...

The second law of thermodynamics demonstrates that "wasted" energy tends to disperse evenly. And if this "wasted" energy is in your house, it simply keeps you warm. More importantly, it keeps your normal heat source from turning on. Let's see how it plays out in a real home and why saving energy by turning off the lights is mostly an illusion.

If you have a home in the northern latitudes which is electrically heated much of the year, you are a net consumer of heat. And the nice thing about heat is that It doesn't matter where it comes from. And that's the key.

Take a light bulb that's only 10% efficient. That means 90% of its energy is converted directly to heat. So what happens to that heat? It spreads out through your house and slightly delays your normal heating system from clicking on.

And what about the 10% of the energy in the form of visible light? Virtually all of it strikes objects in the house. It too is converted to heat. The ONLY ineffectiveness of a light bulb in a northern home in the winter is the light that escapes through the windows, which is a VERY small amount. Even THAT can be stopped with curtains making ANY light bulb 100% effective at producing heat. Here's how Wiki explains it... Efficiency versus Effectiveness.

Why do I qualify this with northern homes and winter? Because if you have to open the windows to be comfortable, you lose the advantage. And if you have to turn on the air conditioning, this "effectiveness" actually becomes a small liability. So those of you in Florida and south Texas... never mind.

It's all about heat, where it moves and how we store it. But for most of America, much of the year, energy efficiency is very much an illusion. Effectiveness rules the day because we actually USE that "inefficient" heat.

And if your windows are closed but your heat is NOT turned on? Or not turned on until later at night? Those appliances are still 100% effective. That's because they are helping keep the house warm. They are one reason your electric heat hasn't come on yet. If that heat doesn't come from one source, it has to come from another.

But what if you're a bit on the warm side in the late afternoon but you haven't opened the windows? Again, it doesn't matter. This thermal inertia will delay heating later on. As long as you don't have to cool your house, everything is 100% effective. Let's take a couple more examples.

Electric blanket - 100% effective. If you turn it off, the electric wallboard heating will kick up 100 watts to compensate: net cost of blanket electricity for the same comfort level - zero.

TV, DVD & computer - Left on all the time? No problem, as long as the air conditioning doesn't kick on.

Hair dryer - 100% effective (and only used for short periods anyway), so get every hair in place.

Electric toothbrush - Yep. Even its charger is a perfect machine in this context.

Refrigerator - 100% effective. This is one of my favorites. What does a refrigerator do? That's right. It compresses gas to pump heat from the inside to the outside of the icebox. Where does that heat go? It heats the kitchen! Even the compressor is 100% effective! Once again, it saves energy that might come from electric heat.

Why do I keep referring to electric heat instead of oil or gas? That's because in the past gas has been far cheaper than electricity per BTU. This made electrical devices a little less "effective" (and a little more expensive) in producing that "wasted" heat. Unfortunately, cheap gas is history (update - well, it was in 2007). The cost of oil and gas heating now approaches that of electricity (at least during the price spikes which are likely to be more common in the future). So for many, there's no big difference. Leaving your TV on is almost as cost effective as buying natural gas.

Another even more significant exception is if you warm your house with a heat pump. Heat pumps with a good source are three times more effective than electrical resistance heat so two-thirds of the stated saving ARE real. CFL and Energy Star DO represent significant saving in this case even though one-third of the savings is still an illusion. Your mileage may vary but it will always be less than claimed by these "expert" sources.

With electrical resistance heat, this "effectiveness" creates the strange situation where you could turn EVERYTHING in the house OFF (except for the electric heat) and set in the dark for a winter month with no entertainment or hot food - and your power bill would be EXACTLY same. Try it sometime. You'll see.

This also means you could go out and buy the most efficient light bulbs you could find and all new Energy Star appliances; STILL, the power bill would be EXACTLY the same. So enjoy your gadgets and think twice before spending extra for "efficiency". Spend your money where it counts.

And where might that be? If there's little advantage to "efficient" appliances, how can we save energy and money? That's another blog post but start by taking a look at the heat leaving your home through the walls or down the drain as hot water. Those two are your biggest loses.

Heat and air conditioning use 50% of home energy. Better insulation and sealing can save up to 25% of your energy cost for the typical home. But make sure the house still has reasonable ventilation - especially in radon areas. And hot water is about 13% of your energy use, so again, use it carefully. It's not effective to heat up the sewer drains.

Which brings up one important exception to this "effectiveness" rule - the clothes dryer. It blows it's heat outside and also brings in cold air - you lose. It's a good reason to get a clothesline. Or use the dryer sparingly.

And if you still want to buy some of those CFL bulbs, put them outside. That's one place where ALL the savings count.

There you have it. Now you can sleep better (and warmer) knowing your heat isn't as "wasted" as you thought.

OK. If you still want to know how much of that 65.7 KWH you would save by buying that bulb, multiply it by the ratio of cooling days over days in a year (365.25). The extra air conditioning load will be offset by less probable need for light in the summer. For me in Reno, Nevada that extra efficiency can be used about a quarter of the time (in the summer) which is probably about average for America. This makes WalMart's claim overstated by four times - you decide if that bulb still makes sense.

But why would Fast Company, WalMart and Energy Star not point this out? Simple. It would make the story less exciting, WalMart would sell fewer light bulbs and... and... and I don't know WHAT'S wrong with the Federal government.

So from now on, don't let some slick magazine make you think a new light bulb will solve all your problems; don't expect WalMart to always save you money. And finally, don't expect the government to set them both straight. When you hear about efficiency, think also about effectiveness.

And quit worrying about your household appliances. They are almost perfect machines much of the year. No matter what their efficiency rating. Please leave a comment if I've missed something.

11-30-11 - The best counterpoint to my post that I've seen so far:

The Math Changes on Bulbs - Wall Street Journal

03-12-12 Ready for $50 Light Bulbs?


  1. Charles Fishman's response to my post...


    You raise a good point, but your "lack" of savings is equally

    We live in Philadelphia, hardly a temperate part of the country, but
    we typically only use our heat Nov/Dec/Jan/Feb and some of March.

    By your lights, we'd be best off running all lights in all rooms all the times those months, and presuming that would help reduce the heating bill. But that of course is silly. I walk through the house turning off lights every morning before work (we have a 5 year old and an 8 year old; for them light switches only go one way). All day long, I work in my home office, with all the lights off, or just one light on in my office, and the heat pretty close
    to off.

    That light in my office, and the lights in the kitchen and bathroom, are CFLs. So, I'm not saving any thing by using them? I'm not saving anything by using them in the wide large hallway
    fixtures, in the outdoor lights (of which there are five in this
    house)? In the kitchen ceiling lights, where the "can" bulbs do
    produce heat, but not useful heat?

    Pshaw. You are right that incandescents provide some heating. But often it is lost — I don't need my ceiling heated, where the ceiling fans are.

    The most important point of your critique is, it's much more
    complicated than a straight-forward multiplication problem. I should have acknowledged that, and I'm sorry I didn't.

    The cooling savings in a lot of subdivision homes from Virginia south and west are huge
    from April through September. I grew up in Miami, so I know how
    significant that can be.

    It's a complicated calculus. But replacing CFLs is not in any sense
    energy neutral. (Plus, of course, not throwing away bulbs has its own savings.)

    Thanks for reading and taking the story so seriously.

    Charles Fishman
    Fast Company magazine

    And my reply...


    Thank you for the quick and cogent response.

    > You raise a good point

    I'm impressed you understand what I'm talking about. Far less than half the people I explain it to "get it".

    > but your "lack" of savings is equally exaggerated.

    No exaggerations at all. I assume each of the following point are examples of my "exaggeration" so I will address each in turn.

    > We live in Philadelphia, hardly a temperate
    > part of the country, but we typically only use
    > our heat Nov/Dec/Jan/Feb and some of March.

    But how much of the year and / or day and night do you NOT cool your home? THAT is the key.

    The lack of savings doesn't just occur when you're running the heat. One of the reasons you
    don't run the heat during part of October and April is because of these inefficient light bulbs and other internal electrical appliances.

    Look at it this way, if the power totally failed in late October, would you be uncomfortable in
    your home (especially at night)? Probably not.

    Here's another good example. I, like you, only run my electrical heat from about November to March, but my electrical bill during October and April only falls to about half of what it is in

    Yep, that's right. About half of my energy use in January is from everything ELSE in the house. Now excluding losses from hot water down the sewer (as mentioned in the blog post), all of THAT energy is the main reason I don't run the
    heat in October and April. The same is true to a lesser degree in September and May.

    I didn't state what YOUR lack of saving might be, just that they are ZERO if you're not cooling
    your home - no exaggeration.

    > By your [rights] , we'd be best off running all
    > lights in all rooms all the times those months

    Yep. Well, not best off. You'd have trouble sleeping with all those lights on, but there would be very little difference in energy consumption.

    > and presuming that would help reduce the
    > heating bill. But that of course is silly.

    I agree. Silly. But I DIDN'T say running lights would help REDUCE the heating bill, just that it won't make it any greater. More to the point, I said CFL lights wouldn't reduce the heating bill either. It's just that your magic light bulb would have zero advantage under those conditions
    - that's a major difference in claim and no exaggeration.

    > I walk through the house turning off lights
    > every morning before work (we have a 5 year old

    > and an 8 year old; for them light switches only

    Wisdom from the action of babes. I'm not saying it helps, just that it doesn't hurt either - as long as you're not cooling your house.

    > That light in my office, and the lights in the
    > kitchen and bathroom, are CFLs. So, I'm not
    > saving any thing by using them?

    Unfortunately, no. If you're not cooling your house - no savings. No exaggeration.

    > I'm not saving anything by using them in the
    > wide large hallway fixtures

    No. If the hallway is within the house, any "loss" helps heat the house in general.

    > in the outdoor lights

    Ah! You got me here. Or did you? If you read the blog post carefully, I specifically say, "if
    this "wasted" energy is IN your house". Outside lights WOULD completely benefit from CFL or being turned off, but I wasn't talking about OUTside - so again, no exaggeration.

    > In the kitchen ceiling lights, where the "can"
    > bulbs do produce heat, but not useful heat?

    Heat produced in the kitchen ceiling is by no mean "useless" unless you have no insulation in
    the ceiling. And even with poor insulation, people still stay comfortable whether it's from the lights or baseboard heat. insulation or lack of it cuts both ways.

    > Pshaw. You are right that incandescents provide
    > some heating. But often it is lost — I don't
    > need my ceiling heated, where the ceiling fans
    > are.

    Pshaw back at ya! Much of the "loss" from light bulbs is in the form of infrared radiation which
    projects away from the ceiling just as the visible light does.

    OK. I'll grant there are MINOR differences caused by stratification but that heat source too is "inside the box" and contributes. In any case this factor hardly constitutes an
    exaggeration of my claim.

    > The most important point of your critique is,
    > it's much more complicated than a
    > straight-forward multiplication problem. I
    > should have acknowledged that, and I'm sorry I
    > didn't.

    Thank you for the admission, but I don't believe you yet understand the significance of the error.
    Because it's difficult to quantify, it's easier to rationalize. Have a care.

    When you add in the final factor that light tends to be used precisely when heat is needed (night time), your error is NOT just a few percent. It's more on the order of 50 to 70 percent for
    much of America.

    And if 100 million people actually buy these CFL bulbs on the strength of your math, doesn't that make you just a shill for WalMart? Intended or not?

    More importantly, what if others reading the article misdirect resources better applied to
    other methods of saving energy? We need to do the things that COUNT!

    > The cooling savings in a lot of subdivision
    > homes from Virginia south and west are huge
    > from April through September.

    Yes. But that's EXACTLY when lights are least used and therefore the savings less of a factor.

    > I grew up in Miami, so I know how significant
    > that can be.

    Good counter-example, but again you probably didn't use lights as much as you do now either - especially in the winter.

    > It's a complicated calculus.

    Actually, the important parts are only algebra. It's just that the results will vary greatly by
    location and use.

    Here's one more way of looking at it. Think of a house as a closed system with electric heat. Would you agree an electric blanket being turned turned on or off in the winter would have ZERO impact on the power bill? Your answer is key.

    Now just replace the blanket with a light bulb. It's the same thing if the curtains are closed. All the energy stays within the system.

    After that it's just a matter of season, temperature, natural light and comfort level.

    > But replacing CFLs is not in any sense
    > energy neutral.

    It is in the winter. But let's consider the whole year. These bulbs get used most when they have the least advantage and least when they have the most advantage.

    And what if the savings are only HALF of what you represented? Does your audience need to know?
    Does WalMart need to know? What if we can bring some real talent to bare on the topic. I'll make
    a public apology if I'm wrong. Will you?

    > Thanks for reading and taking the story so
    > seriously.

    You're welcome. Actually, I've taken the topic seriously for a long time. I've been disappointed by Energy Star and Popular Science
    for years. It's just that your article brought out the blog in me. For that I'm in your debt.

    Thank YOU.


  2. Here is my response on the topic at alt.energy.home ...


    I was surprised at how many responded without even reading the blog post. For those, I'll make it easy and paste the entire post on a fresh thread. You'll still have to go the blog for Charles Fisher's (author of the article) comments and my response.

    I was honestly hoping for some good analysis, not just on the physics, but on the economic and ecological aspects of misdirecting our political resources.

    But let me address your comments anyway...

    CJT posted...

    > People generally only need to heat their houses part of the year;

    Noted in the blog. But the advantage occurs NOT JUST when heat is required. Typically, more than half of home electrical consumption stays in the home in the form of heat until lost from lack of insulation. So these bulbs (and other electrical devices) are a significant factor in why you DON'T need to turn your heat on. And that's the point.

    > Many people heat with gas, propane, or heating oil.

    This too was addressed in the blog. It should also be noted that the cost of natural gas heating approached that of electrical heating last
    year when the natural gas price was near it's peak. The price of
    natural gas is more likely to go up in the future, than down.

    gfretw posted...

    > That is absolutely true as long as you have the heat on.

    And more as noted above.

    > I doubt those people in San Diego or LA turn the heat on very often
    > and then it is probably at night when they are sleeping anyway.

    True. And noted in the blog. But heating from lights during the
    evening delays that heat from coming on later - thermal inertia.

    As long as you don't require significant cooling, light bulb energy is used effectively.

    Joe Fischer posted...

    > Just that much of California doesn't need heat much of the year.

    More than you might think - especially in the mountains. I've spent much of my life in norther California and heat is used for many months of the year. Truckee, California is often the coldest spot in the lower 48 states.

    Graham posted...

    > Since when did using less electricity cost more ?

    You fail to understand. The electricity doesn't cost MORE. I never said it did. It's just that it doesn't cost as much LESS as they claim. And the margin of error is significant and material. It's that you're not using as much LESS as you think. And you may be
    paying more for the bulb than you save in energy.

    > Not very helpful in the summer is it ? You'll need more A/C to get rid of that heat.

    Yes. As noted in the blog post. But for much of the US, A/C is only needed a few hours a day for a few weeks of the year. And there's an inverse relationship between the need for light and A/C as summer provides more natural light. During these extra hours of light, excess heat is not an issue.

    Gordon posted...

    > Incandescent lightbulbs are terrible heaters.

    Wrong! As noted by others, light bulbs are EXCELLENT heaters. Much of the non-visible energy actually takes the form of radiant infrared. And since light tends to be used where humans are sitting (if applied properly), this heat is EXACTLY where it's needed.

    Vaughn Simon posted...

    >> The fact is, unless you are cooling your home, there is ZERO savings.
    > Nonsense. The only time that is true is for the actual time that you
    > happen to be heating your house with electrical resistance heating.

    Not nonsense at all. You don't think all those electrical appliances in your house help keep your heat from turning on? Let me sell you a more effecient electric blanket.

    > There is no point in reading your "blog" because you don't
    > understand basic physics.

    How do you know WHAT my understanding is until you're read the blog?

    I'd like you to point out even one material error. Each point in this thread was addressed and properly qualified in the original blog post BEFORE this thread was started.

    Tony Wesley

    >> Will someone please tell me what I've missed before this becomes law?
    > An education?
    > Others have already adequately pointed out the flaws in your post.

    Then why bother posting a personal attack? As a typical American,
    your lack of understanding is the VERY point of the blog post. It's
    the only thing making your comment useful and relevant.

    Deputy Dumbya Dawg posted...

    > Agreeing with you winter heated home case above

    Thank you for your understanding and acknowledgement.

    > [Except] In places where there is no heat or air conditioning just a grass hut with a bulb

    An exception also noted by the author of the Fast Company article, Charles Fisher. (Effectively) outside light bulbs keep 100% of stated savings. But my challenge is to the Federal Government's (Energy Star) stated savings IN the typical American home. The challenge stands.

    > A watt saved is a watt earned.

    Unless it's a watt that must be replaced by your electrical heating system.

    Derek Broughton posted...

    > How so. I use less power, I spend less money. It's working really well for me!

    Sorry. To a significant degree, your savings are an illusion as long as you're not cooling your house. And the government should have told you about it BEFORE you bought that CFL light bulb.

    > For the heating months...

    For MORE than just the heating months.

    > when you put your heat source near the ceiling, too much
    > heat escapes through the roof

    Only if your ceiling insulation is less effective than the rest of the house insulation. And only for the heat that is NOT radiant as noted above.

    >> Will someone please tell me what I've missed before this becomes law?
    > Common sense.

    Then you think this proposed law reflects common sense?

    Unfortunately, sense isn't that common.

    Paul M. Eldridge posted...

    > There's some truth in what you say but, on balance, you'll find the negatives far outweigh the positives.

    How can they OUTweigh? Energy Star set the bar by claiming certain savings and WalMart is selling light bulbs based on the bad math. Any non-existent saving by definition can not be negative. I just need to demonstrate that for SOME people the lack of saving is significant and material. For many, these bulbs will NOT be cost (or energy) effective. The rest of the country SHOULD buy the bulbs. We just need to know which group we're in.

    This is an excellent example of, "YMMV - Your Mileage May Vary". I
    just believe if the federal government is going to spend millions of tax payer dollars, they should not lie to us about our true savings.

    > In summary, incandescent lamps are a poor choice for consumers and far more so for utilities and our environment.

    This is not true for everyone. And we should be informed when it
    isn't. Especially when we are paying for the information.

    Jack posted...

    > Your analysis is quite correct in that saving energy on light bulbs only to spend it on heating is a net zero gain.

    Thank you. The reasons are obviously, not as obvious to everyone.

    > To be honest though most office buildings have a net heat
    > excess during almost all of the year because of
    > the large number of humans contained therein.

    I agree. This is why virtually all office buildings use fluorescent lights. But the blog post is not about industrial or office structures.

    It's about Energy Star recommendations, Fast Company and WalMart, which means it's about the typical American home.

    > It would seem that if The Bush Administration really
    > had the slightest interest in the energy independence of
    > The United States they would provide us with some
    > guidelines on conserving energy.

    Jack, you nailed it! THAT'S IT! THAT is the point of the post!

    We need good information about how to save energy and money and not
    some illusion, or worse, some law based on bad math.

  3. Copied from Sudden Technology blog to keep all this together -

    Anonymous posted :

    Note that most homes heated by electricity use heat pumps. Heat pumps can be expected to put three Watts of heat into the house for every one Watt of electricity consumed. By comparison, One Watt of electricity consumed by a light bulb of any kind puts about one watt of heat into the house, assuming it is not in a porch or recessed fixture. Therefore it costs three times as much to heat with a light bulb, or any other electric appliance for that matter, than to use the house's heating system for heating. It is fairly rare to find a house that is exclusively heated with resistance heating, particularly in cold climates due to the high cost. The distinction that has to be made for what you wrote is applicable to resistance heated, versus electric in general, that includes heat pump systems. Electronic retrofit devices that can be added to old appliances improve perfomance and reduce energy consumption and work great, but they have not been promoted, and I think have been discontinued. The government and industry just want to sell new appliances because that is what can be taxed or profited from.

    Good point which was also brought up and addressed at...


    >Paul M. Eldridge posted...
    > Let me elaborate on my own situation, as it happens to be the one I
    > know best. I heat my home with a heat pump that provides, on average,
    > two and a half times more heat, per kWh, than electric resistance

    You provide an excellent counter-example I hadn't considered. Heat pumps are wonderful and efficient machines and you show CFLs are indeed the way to go in your home.

    But I think you would still agree, not ALL of the savings calculated by Energy Star go into your pocket. Even though cost effective, your heat pump still has to replace that lost heat at the cost you've nicely defined.

    Now if we could just convince 100 million home-owners to convert to
    heat pump.

    As noted, a heat pump helps but only reduces the error by two thirds under the best conditions. One third of the CFL savings are still missing.

    And good point about the tax and profit motives...

    Thanks for the comment.

    Sudden Disruption

  4. I am just curious if any one knows how many Kilowatts are used to make CFL's vs. incandescent lamps.
    I wonder if CFL's cost more energy in production than they "save" in homes.

  5. Neverworthy

    A worthy question...

    I don't know the answer.

    Why not present it to


    Sudden Disruption

  6. Rod, I agree with many here:
    you show bias through exaggeration and persistently erring on the side of inefficient (in terms of light output per unit energy used) bulbs. You zealously point out that during some parts of the year heat from inefficient bulbs supplants the need to run other heating devices (presumably at night). There is a corresponding savings from efficient bulbs in supplanting the need to run cooling devices. If such a supplanting effect has any significance at all, efficient bulbs absolutely would have an effect even when not cooling your home since the reduction in heat they produce would sometimes circumvent the need for cooling.

    Furthermore, cooling is considerably less efficient than heating, so the savings in circumvented cooling far outweighs the savings in heating on a per unit heat energy basis.

    Furthermore, homes are simply not 100% efficient, so they do not necessarily store heat well. Joules added to a hot home during the day are effectively lost by the time a cool evening arrives. (Though admittedly most lighting is done at night, which is when the inadvertent heating IS useful.) I am curious if you know of any empirical evidence that heat generated by bulbs during the day has a measurable effect at all on the thermal energy stored in homes 1 hour later--I don't know of any evidence one way or the other.

    Also, similar to the previous person mentioning heat pumps, many people use local devices (closing vents in unused rooms, space heaters, electric blankets) to only heat controlled areas during nights. The same people are probably those who are using CFLs. For them, uncontrolled heat from less efficient bulbs is simply wasted.

    Finally, there are outdoor bulbs.

    So, while I think you make a worthwhile point in mentioning that "inefficient" bulbs should not always be dismissed as inferior, I think you have done a disservice to your point by skewing facts in the opposite direction.

  7. > you show bias through exaggeration and persistently erring on the side of inefficient bulbs.

    I'm afraid you've missed the point. My post was not about any given energy calculation, exaggerated or not. My point is about thinking INside the box. It's about the EFFECTIVENESS of energy savings (as defined in the Wiki link), as opposed to the efficiency.

    Most media reports totally ignore WHERE these bulbs (or other energy sinks) actually live, and the effects that will have.

    True. My ideas don't matter in south Texas. But when heat is needed, effectiveness can become FAR more important than efficiency.

    We do not live in a vacuum. Even if our bulbs do.

    Thanks for the feedback. - Rod

  8. Where the heat is used is important and being covered by a 100 watt electric blanket can be much more effective than a 100 watt light bulb on the ceiling. However, I basically agree, we need to make realistic calculations.

    One particularly important one is the amount of light we are talking about. Two of the CFLs I installed a few months ago are now down to what subjectively looks like less than a quarter of the light output. They are really dim. It seems to vary but in this cold climate they clearly don't work outside for most of the year. The ones in heated locations fare better, but still decline in output considerably after some months. CFLs put out less light at time of replacement than they do when new. I would like to see the "area under the curve" considered when talking about CFL efficiency. What exactly is the total amount of light they put out over their lifetime? We need to know because the brightness when new is a useless figure by itself.

    I just did a guestimate calculation of this and it would seem realistic to say that CFLs are perhaps only 30% more efficient in light output over their lifetime. The question is does the higher cost of acquisition and recycling eat up that difference? I would wager that if we dared to factor in the cost to China's carbon foot print that we are making a step backwards.

    If someone wants to refute my claim of low efficiency, I would be very interested. However, please give figures that are relevant in my part of the world. Below freezing outside (8 months) and a nice rural inside temperature of say 15°C (60°F).

  9. Ole Juul,

    I'd never heard about the decreasing light output of CFLs. Or their temperature sensitivity. It should be documented if it's the typical case.

    And 8 month of frost? You must live way north - Norway? That would be a perfect place to use 100% effective incandescents.

    You comments on China are consistent with my point. We need to look at ALL of the factors involved, or simply live a delusional life.

    BTW, WalMart here no longer carries incandescents.

    Thanks for the feedback.


  10. I purchased an AmWatt meter at the home depot.

    All of the appliances I tested were very accurately rated. My toaster, for instance, is rated 1000watts tested 997. As it warms up it drops a few watts below this.

    The 40 watt light bulb is exactly forty watts. 60 halogen is the same.

    It surprised me that the Philps Marathon decorative twist CFL labeled "12 watts" actually pulls 40 watts. Old CFLS and new ones all tested about at the label times a factor of -- is that PIE?

  11. PIE may be Peak Current Voltage as opposed to an RMS measurement. The bottom line is, how much are you paying for the energy you're using (RMS) and what is the device measuring? Apples to apples?

    Or else this whole CFL thing is a scam to sell us new light bulbs. :)

    (which it may be in any case).

    Thanks for the feedback.

  12. what about the inefficiency of electricity generation itself? Your power plant loses like 70% during generation/transmission, so depending on your electricity-run light bulbs for heat is far less efficient than depending on your furnace, whose loss is somewhere along the lines of 30%.

  13. Its really just watt for watt right? If I have ten 100 watt light bulbs on its the same, more or less, as having a 1000 watt electric heater right?

  14. Yep. Well, except for any loss of light out a window which would be a tiny percentage of total energy. - Rod

  15. Sounds like somebody lacks some serious real world experience. Almost every light in the ceiling is a hole in the ceiling. Few homes have very well sealed light fixtures, we seal them almost every day. Your "thermal inertia" might work off of your paper, and outside of your wonderland. But here in reality, where the home already has a stack effect pushing air out past your lights/fans. A large majority of heat created by a large majority of light fixtures in homes right now is blown right through your ceiling, never coming back in. A standard home cycles it's air every 3 hours, carrying much of your created btu's outside, this has to happen for you to breathe fresh air. Fact is, when you produce 20 lumens with 1 watt, doesn't matter if you live in alaska fool, getting a light that takes 2 watts to produce 20 lumens would be dumb. You can heat your home 100% from wood, gonna leave your lights on all day talking up your new fangled heating system? Electric heaters are designed to put heat where it will matter, your type of thinking you could tell everybody to pull the blower motors off of there furnace because the same btu will be in the house (law of thermodynamics). While those of use that understand how to use the law will leave the blowers pushing warm air towards our skin.

  16. Challenged is what the heading should say. You really don't realize commercial buildings exchange their total air sometimes more than once an hour depending on occupancy. Residential it is 1 exchange every three hours and that is the standard. Older homes can exchange ALL of their conditioned air once an hour. Ever heard of convection? Doofus! Well you got a page with comments on it, either on bad choice of subject matter by you, or you areally are a complete moron.

  17. Just one question - does it matter to poor insulation or air cycling if the energy is delivered from a light bulb or electrical resistance heater at the same location, at the same wattage? NOW do you get it? Rod

  18. Let me see if I can add a good point (or if not, have it explained to me where I'm wrong.) It seems to me that there are three cases:

    1. Cold weather, heating system is running: You're right on target Rod. Doesn't matter whether the heat comes from the bulb or the heating system, unless the bulb is placed outside; if inside but badly placed, it will only waste a slight amount of heat.

    2. Hot weather, A/C running: Your post correctly anticipates that the waste heat from bulbs will make the A/C use more energy.

    And here is the good point I hope to add:

    3. Temperate weather (about 70 to 85 degrees): Neither the heat system or the A/C is running. In this case, the heat from the light bulb is largely wasted because it will tend to dissipate before cold weather comes, when it would have delayed the turning on of the heating system.

  19. Very good point. It is the "boundary" case. The edge occurs if you have to open the window to cool the house. If not, that heat is saved for the evening when the house cools down.

    I want to congratulate you on understanding not only the point this post, but the exceptions of the physics. Only about one in twenty of those I bother to explain this to actually "get it" as well as you do. And what amazes me is the science media (and Energy Star) who continue to ignore these important factors when calculating their "savings".

    Thank you for the astute comment.