LED Light Bulbs, the numbers

I recently picked up a couple of LED light bulbs that are starting to become more popular in Japan. After comparing a few different options from various major manufacturers, I settled on the “40 Watt” (450 lumen) bulbs made by Panasonic. The main draws for me were the relatively high efficiency (more lumens per watt) compared to other LED bulbs, and the fact that they emit a warmer orange color rather than the harsh bluish light typical in CFLs. Another draw was the fact that these bulbs are rated to last 40000 hours, or about 5x as long as CFL bulbs, which could reduce waste.

On the other hand, at around $30 a pop (2380JPY, to be exact), they’re pretty expensive as far as light bulbs go. Are they worth it? I decided to run some numbers, comparing the LED bulb I got to a traditional incandescent 40w light bulb, as well as “40W”, “60W” and “100W” CFL bulbs. The results are in this spreadsheet below (see the original document on Google Docs).


  • klmh – “klmh” stands for “kilo lumen hours”, and can be thought of as the total amount of light emitted, if it were possible to gather light over time and put it in a box. One klmh equals the amount of light emitted by a 1000 lumen lamp over 1 hour, or a 1 lumen lamp over 1000 hours. Technically, a lux is a better unit with which to measure total light emission, but that information wasn’t available (while lumens were) so I used Kilo-Lumen-Hours to compare bulbs of different brightnesses.
  • Power costs – I used $0.15 per kWh. Actual energy costs vary from around $0.10 to $0.20 in the US. See prices for September 2010. Calculating the cost of energy for off-grid systems is much, much harder, and would vary widely from system to system, so that is left as an exercise for another day.
  • Annual usage – To calculate “costs over 5 years”, I assumed an average 5 hours of usage per day, or 9125 total hours of usage.
  • Total costs – The “total cost” calculations combine the amortized cost of the bulb with estimated energy costs (again, at $0.15/kWh).

I tried to compare the bulbs from a wide range of perspectives, and ended up with all sorts of numbers. I’ve highlighted the ones that I think are relatively informative, but, as you can see, some bulbs do better in some comparisons, and do worse in others. In other words, there’s no clear all-around winner.

Efficiency – In terms of efficiency, the “40W” LED bulb (65.22lm/W) was bested only by the “100W” CFL bulb (67.33lm/W). In reality, the LED might perform a little worse, because LED lamps have more directed lighting patterns, so despite what the lumen rating is, the actual total amount emitted may be less than CFL bulbs. As a side note, it was also interesting to see that the efficiency of CFL bulbs improved with increase in wattage. I think this is because fluorescent lights become more efficient the longer they are, and higher wattage CFLs simply have longer tubes.

Cost – If all you care about is having a light bulb –any light bulb regardless of brightness– in a socket, LED is by far the cheapest option. Even though the upfront cost of the bulb is considerably higher than the alternatives, the additional expense is offset by the bulb’s long lifespan and low energy usage.

On the other hand, LED bulbs are relatively dim compared to the brightest CFLs, and if you must have lots of light, CFLs are cheaper for the amount of light you get. This last point is important. Even though a 26W CFL bulb has 1/10 the cost of a 6.9W LED for the same amount of light, the simple fact that it uses more than 3.5 times as much electricity can not be overcome. Having a 26W (“100W”) CFL in that socket will cost you more than twice as much as using a 6.9W (“40W”) LED bulb. But if you must have that much light, it is cheaper to use one “100W” CFL bulb than to use multiple “40W” LED bulbs.

More is more, less is less
Retailers often try to get consumers to buy more stuff by offering lower per-unit costs when purchased in bulk. While buying in bulk may lead to real savings, such deals can also be a pitfall that leads to excessive consumption and spending. The question to ask is, “Do I have to alter my behavior, in order to take advantage of this deal?” If the answer is “yes”, it is best to stay away from bulk purchases. For example, let’s say a grocery store has a deal on ice cream, such that if you buy 2, you get 1 free. The question is “Would I eat more ice cream if I bought 3?” If the answer is “yes” (and let’s be honest now), just buy one, because one is still cheaper than two, in absolute terms. On the other hand, if you’re dealing with something like toilet paper where abundance probably won’t lead to higher consumption, buying in bulk might actually save you money.

The same applies for lighting. If you can get away with less lighting, it will save power and money. Don’t let the illusion of better “value” trick you into consuming more unless that is really what you want, because you will pay more for it. Using one “100W” CFL bulb for 5 hours a day over 5 years will cost an estimated $38.18, while a “40W” LED bulb used for the same duration will only cost $16.29, even when factoring in the cost of the bulbs. Yes, you get less lighting, but you get less for less, while more costs more.

Lighting accounts for 12% of domestic electricity consumption in the US, and I would argue that that makes it a ripe target for reduction. While current trends are towards improving efficiency, Jevon’s paradox warns us that efficiency may in fact increase consumption. If that is true, it seems to me that the true path to reduction is, well, to reduce. That is, rather than merely swapping 60W incandescent bulbs with “60W” CFL bulbs, consider using “40W” bulbs. Instead of having area lighting consisting of 5 or 6 bulbs, consider having 5 or 6 individual lamps located strategically, so that only localized areas that actually need lighting are lit at any given time. Or, for that matter, turn those lights off entirely, and go to bed early. Artificial lighting can interrupt our natural circadian rhythm, leading to sleeping disorders and other maladies. So going to bed early and getting some extra sleep can save your health and the planet. Now that’s what I call a good deal.

35 thoughts on “LED Light Bulbs, the numbers

  1. I live in an area which has recently banned all incandesent bulbs above 60w in power, essentially forcing people to either add more lights to their situation, or switch to CFLs which produce the same amount of light, with a lower wattage, or go LED.

    My biggest problem with this is that CFLs have mercury in them – enough to cause damage to the environment should they be disposed of improperly. We use them at the paintball field I work at, whereby we can light up our entire base camp area with a tiny 1000w generator and still have a lot of available power left over. All our CFLs are in places where they cannot be broken. And they will be responsibly recycled at their end-of-life.

    It’s all the other disposed-of-in-garbage, broken, and tossed that I’m worried about.

    Mercury poisons water at an incredible rate… I live next to a lake, and that’s where my drinking water comes from.

    • I have been slowly switching to the CFLs and some of them have already expired. When I take them to a disposal center, they don’t know that they should be treated any differently and just pitch them into the trash. I’ve noticed that this is true for the CFL tubes as well. Landfills and waste management companies don’t seem to “care” enough to be informed and manage disposal correctly, negating any real effort to dispose of properly. This is very disheartening when so many of us are trying to be responsible.

      • Way back in teh 80’s out little town started a recycling program. They put out bins, separated for clear glass, green glass, brown glass, cans etc etc. The rules stated that they must be clean, the labels taken off, etc. It was a pain, but those of us that cared did it. The containers eventually went away.

        A while later, I was talking to a guy who works for the town. He said that they did not get enough recycle stuff, so they just brought it all to the dump and burried it. Pissed us off.

        The town I now live in does a pretty good job of recycling, including batteries and CFL’s. The only weaknessese are that they only take some of the plastics, and they must be in “Bottle Form”, so non bottle PETE or HDPE will not be accepted, and in fact are removed if put in.

        Still, we do pretty good here.

        on a kind of oddball side note, a while back there was an article comparing recycle rates between the different states. A twenty something kid tried to tell tme that our state was worse than the neighboring state he was from because our percentages listed were worse. I asked the logical question “percentage of what?”. He could not answer. He did not believe it mattered. If it is percentage by weght, or volume, of all waste produced, then the next logical question is which state produces less waste. If it is a percentage by “recyclables” then which state produces less. And does this include industrial waste? How about industrial waste that is not created because of good processes? Lack of knowledge about how a number is produced can cause a faulty belief.

        Then again, lets say a state recycles 90% of their waste. If the number goes down to 80%, that does not mean teh state got worse, it could be that the state vastly reduced the amount of waste, but did a little better on reducing the the recyclable waste. Conversly, iff the number went to 95% it could be that the state increased the amount of total waste, only tht the recyclable waste increased faster.

        The joy of numbers.

        I think my morning coffee kicked in.

        Oh, and excuse the spelling, for some reason the zoom feature is not working correctly so the letters are too small to see easily.

        Bob L

  2. I’m not sure how they calculate bulb life (is it considered constant run-time? Or is it with a given number of cycles switched on and off over X amount of time?) but remember that switching CFL’s on repeatedly (i.e. when you turn the lights on when you enter a room and turn them off when you leave, to save electricity) drastically reduces bulb life. So maybe CFL’s last a lot fewer hours than projected (unless you just leave them on a lot, which is also a bummer, for other reasons)

  3. If possible, can you get a 10W CFL and compare it to the LED light? Since the CFL spreads light everywhere, and the LED is more directed, let us know if the light for the LED is more usable. I would expect the LED might seem brighter at your work area.

    It is good to see that consumer LED lights are finally getting to be as efficient as the CFL’s, and will probably far surpass them shortly. I had not seen the specs on the newest consumer LED bulbs. Now if they can just get the price down without killing quality. When CFL’s first came out they were very expensive. The ones I saw met their specs, including lifetimes, fairly well. Eventually, the prices came down decently, and you could get high quality ones from your power company for about what the cheap ones are in the stores now. But the ones you can buy now are of variable quality. Sometimes they last, sometimes they don’t. They all get dim over time, sometimes by quite a bit long before they get to their rated life (another advantage of LED’s). LED’s also dim over time, but at least the quality ones last a LONG time.

    Bob L

  4. I could not find the new Panasonic bulbs anywhere on-line here. The best ones that I could find are still not as efficient as the small CFL’s. Soon I hope.

    Bob L

  5. Just a warning at cheap LED bulbs from china: I bought 4 a year or 2 ago and they all died within a couple months. If you’re getting an LED light of some sort, make sure it has either good reviews or a reputable brand. I think they were something like $7 each so not even really “cheap” but the quality was obviously terrible and the result was just more waste.

    I recently switched my 2 fish tanks to LED light strips and I’ve been very happy so far. They’re 12v DC so they can hook up directly to a 12v solar or wind setup, and use about 6 watts to make about 450 lumens and easily replace the previous 25w fluorescent light with roughly the same light. The cost is hard to beat at $10 shipped. I have one left over that I plan to use for outdoor lighting at my cabin but my LED strips are cool white and not the warm white you want inside (warm white LEDs are pretty common though).

    All in all, if you spend a few minutes wiring up an LED light yourself and do the proper research, you should end up with 20-50% power savings over CFL, far less heat, a more compact setup for roughly the same costs.

    As for the simple screw-in bulbs, the tech is still not widely available and prices will probably be half of the current ones next year. Food for thought I guess..

  6. Excellent post.

    I recently got a 7W LED bulb which I used for a short while as the main light in my home office. It was OK but I needed my desk lamp on all the time with it and using a CFL in that was not too pleasant. I swapped them to have the relatively low power CFL (16 W) for the room light and the LED in the desk lamp and that’s a pretty good combination. The light from the LED is very nice when I need it. Maybe I’ll get another LED for the room light.

    As tinysunhouse notes above, switching CFLs on and off will cause some reduction in lifetime though it’s hard to work out the break-even point. Still, I imagine (well, guess really) that the wear on LEDs from switching on and off will be less so, in applications where intermittent light is required (e.g., bathrooms), LEDs win by a slightly larger fraction.

    Your energy cost calculations are for people on-grid. Off-grid things are a little different. Here the energy is “free” but the capability to transform it (power) is expensive – I calculate, for something on 24 hours per day, capital costs of generation are about £60 per watt (roughly $100/W) allowing for the fraction of the time in which PV or wind turbines operate and the cost of batteries, charge controllers and so on. Obviously, reduced proportionally for the hours per day something is actually used.

    This capital cost is equivalent to £2.50/(W·h/day) ($4/(W·h/day)). Say using an LED reduces the consumption from 11 W for CFL to 7 W then the saving would be £10/(h/day) ($16/(h/day)) so any light which is used for more than 2 hours per day should be LED (£20 – what I paid for mine, $30 – what Ryo paid for his) purely from the point of view of reduced up-front capital cost. Any extra life for the bulb and the batteries is a bonus.

  7. Great post with nice summery of data and how it applies to individual and global use.

    In WI I have very few CFL that have even lasted 3 or more years. Four burst in bath/kitch rooms with kids and pets making merc cleanup some what dangerous.

    Last year Menards, costco and walmart all carried 40-60watt equivalents for $10-16 (yes under $20 😉 Menards had the best three (and brightest).

    I slowly replaced bad CFls and went to 40watt around property.

    In below 30’F (6 months in WI) the LED’s are brighter and last longer than CFL.

    At sub $15 and with the health and safety problems with mercury in CFL’s … LED has a bright future.

    But the point you make about reduction here is king. The real reason our energy usage went down is that we reduced the amount of total lights in our house by half. When we lost power for three days a simply 600watt power inverter was enough to run our main area lights,wireless router, laptop (no rifle) and frig from our car battery. So it’s as much a safety as a environmental need.

    In the U.S. use of renewable energy continues to increase but not at a pace that is keeping up with usage and in India and China the numbers are alarming. While every nation plays a game saying they want to use renewable energy this has only increased our fossil fuel use.

    Ultimately the ONLY way to reduce energy consumption is to REDUCE… just easy math that’s hard for a modern world to comprehend.

    The architecture2030.org program further exemplifies some points you made applied to buildings. How simple energy reductions can eliminate 80-90% of our fossil fuel use WHILE our population grow.

    This and many of you’re posts do a great job showing that we can.

    Sadly, reducing, recycling and living with what you need…. is not as sexy, political or media hype like “Al Gore” crying and polar bears dying… so you will not see it on CNN or FOX.

    End rant.

    P.S. I will take a photo of the LED “bulb of choice” I have and post it with a link to here.

  8. in our cabin we have 100% LED for our electric lights. These were modified halogen can lights, to take LEDS.

    I can light the entire cabin for about 40 watts. I have a number of independent lighting circuits based on tasks.

    4 lights above the dinning ares

    6 lights in 2 circuits for the main room

    2 lights for the kitchen area

    1 on a 3 way for the ladder to the loft

    2 in the loft

    1 in the closet/ part time bath area

    all of these are warm white LED we also will fire up an oil lamp now and then.

    I Set up all the light to run at 12 Volts which also saves us power losses from the inverter..and with out the inverter running its DEAD quiet.


  9. In 1982 an economist at a meeting in Canada.
    Proposed that power companies would make larger
    profits, it they could pursued their customers to use
    less electricity.
    The logic being that if they persuaded their
    customers to pay for and fit insulation and more
    efficient heating and lighting.
    They the power companies could put up their prices,
    sell less at a higher price, make a bigger profit for
    doing and selling less, saving on the installation of
    more equipment, saving by burning less fuel and
    employing fewer people.
    These LED lights are guaranteed for a very long life.
    They cost a lot more to buy.
    They run a lot cheaper.
    But, when you look at how long a particular light is on
    over a year.
    How much the light you have costs in electricity per
    Then you have to run that new light (that you didn’t
    need) for a long time before you cover its cost.
    Then a lot longer to make a profit.
    Meanwhile, the power company has cut back on coal,
    switched to burning gas, that’s cheaper, employed
    fewer staff, cut back on new larger generators that
    they would have bought to sell more to increase their
    margin year on year.
    And the shop keeper and importer has made a killing
    as they were an ex works price in China of a few

    • That’s an interesting point. In Japan, energy efficiency is a huge deal because energy costs are much higher than in the US. The end result is that consumers are willing to spend more money on appliances, and replace appliances more frequently to decrease energy usage. I don’t know what the net impact is on the economy, but it certainly seems plausible that increasing electricity cost and lowering usage could still be a net positive.

  10. I hate lights.
    LED book light for reading.
    Cell phone for everything else,
    You grow to love and embrace darkness very quickly. (Not the dark side!)

  11. I ran across this the other day from Wikipedia

    In economics, the Jevons paradox, sometimes called the Jevons effect, is the proposition that technological progress that increases the efficiency with which a resource is used tends to increase (rather than decrease) the rate of consumption of that resource.

    I hope this isn’t set in stone.

  12. Very timely. I just bought an LED light yesterday. I also bought 8 incandescent lights. About a year ago I bought an LED light and it lasted about a week. Thinking perhaps it was defective I bought another and it lasted about a month. I’m not sure they have this figured out yet. I intend to buy some more incandescents so that I’m not sitting in the dark when the ban goes into effect.

  13. if these are for the cabin,why did you go for 110 volt units? have you taken in to account the losses in running an inverter as part of your energy calculations?

    • Good question. The reason I decided to go with AC is because DC is more susceptible to voltage loss due to resistance in cables. So, between losing power to cabling, and losing power to an inverter, I chose the latter.

      In reality, I may use a combination of AC and DC. I’ll use AC in cases where long cabling is required, and DC in cases where I can plug things directly into the battery array.

      • Lol, Ryo, no it’s not. Or very very little at 60 hz, due to the capacitance and inductance of the cables. But anyway good blog. Save yourself some money and stick with DC if it’s cheaper. Ohms law is your friend.

        • Oh I see, maybe you are talking about the voltage rather than the fact tah it is 120v rms vs 12 v. ac/dc in which case you lose 10 times as much for the same power, yeah. 12 gauge wire is 1.8 ohms per 1000 feet though so it’s very small if you are just powering lights. Suppose it’s 50 watts total draining from the battery and 12 volts over the wires so 4.16 amps, and the length of 12 gauge wire is 40 feet total, you’d lose 0.3 volts, or (12-0.3)/12=0.975. So you’d lose about 2.5% of your power. That’s much less than an inverter takes, for sure, and there must be a need to rectify it back to DC before it powers the LEDs which looses more.

          • Well, in addition to the cabling inside the cabin, there’s also the fact that my solar penels & battery array are located in a clearing about 100ft from my cabin. It’s still somewhat of a toss-up, but given that I’d need an inverter for some of my equipment anyway, it seems like taking the hit upstream (i.e. closer to the battery array) would be more efficient…

  14. This isn’t the first place I’ve read/heard complaints about bluish light from CFLs. That’s puzzling to me since every CFL I’ve ever used gives a warm-colored light indistinguishable from incandescent bulbs and I’ve been using them for 10 years. I’ve purchased mine exclusively from Costco. Just FYI.

  15. Excellent post. Very nice to see some real data for informed comparison. I have been watching the evolution of the LED hoping that they would become more readily available and I am encouraged to read that someone in Wisconsin is finding these bulbs in a retail location. That is great.

  16. In my experience, the life of leds is grossly over rated and the life of CFLs is grossly underrated.

    When we moved into our current home, we got CFLs for every fixture (with the exception of some specialtys which weren’t available as a CFL at the time) and 6 years latter, the only bulb replaced was the one I accidentally broke. So far, not a single one “burned out.

    LEDs on the other hand seem to suffer from serious quality control issues. About 75% seem to dim and go out in a period of weeks, while those left do seem to last forever.

    • As for burning out I would have to agree with you. I bought a bunch of quality ones from the utility company in 2002 and 2004 if my memory is correct. There are only two fixtures that we keep on for any real length of time. We have had two burn out. They got VERY hot, buzzed, smelled and were dim. Both of these had truly surpassed the rated life.

      However, I have switched bulbs around a few times. There is one fixture that I use for reading that I want BRIGHT WHITE. The CFL’s dim over time. The last time I swapped, I replaced a 12 watt CFL with a new 9 watt CFL and the 9 watt’r was brighter than the used 12. I tend to swap these at around thier rated life. This fixture would be ideal for a good LED. It is really the only place I would put one right now, until the price comes down. I put dates of when I install them on the bulb with a sharie, then when I swap to another fixture. This makes estimating actual life easier.

    • I expect that the LED’s will go the way that CFL’s did from my experience. They start out expensive, and of iffy quality, then get better, then get cheaper but retain quality, then get really cheap but the quality becomes iffy again.

      I bought all of mine when the quality was high, but the price was cheap. $1.50 for the 20 watt’rs, less for lower watts.

      Bob L

  17. A notable difference between CFL and LED bulbs is that LEDs can be put on a dimmer, while CFLs cannot. That further reduces consumption.

      • I wondered about this, as teh best way to efficiently drive LED’s requires circuitry that would not work with most dimmers, unless teh circuitry was specifically designed to work with them. I have never seen that. I have seen people kill LED automotive lighting thinking they could just dim it with a resistor the way they would with a simple LED circuit. Some circuits this will work with, but the most efficient ones will not.

        LED’s are best driven with a circuit that limits current with adjustments for LED temperature amongst other things. There are a number of ways that a manufacturer can do this. Making a 3-way bulb that works in a 3-way lamp socket would be a great way to set one up, and i suspect that once these things become popular that they will start coming out with 3-way bulbs. There are (or were) some 3 way CFLs available. The other way would be to put a dimmer on the bulb, maybe even radio controlled with the control on the wall. I doubt this will become popular. The most likely way that the companies will do it, in my personal opinion, is to sell fixtures that come with lifetime bulbs. These fixtures would be designed specifically to dim.

        Another way to do it is the way some old fashioned lamps did it. Have three light sockets, each with a different bulb (or not) and have it set up so as you turn the switch, different combination of the two or three bulbs goes on. I set up a two bulb floor lamp this way, but with two toggle switches rather than the complicated three or four way lamp switches (could not find any). I put a 9 watt CFL in one socket, and a 15 watt in the other. By choosing one or the other or both I can change the amount of light from the fixture.

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