# The Big Lie About LEDs

I've had it with LED lamps. The world has been told that LEDs are the future, in part because they are economically the right form of long-term lighting, and there are environmental benefits as a great aside. Well, maybe the environmental argument is true, but the economical one is not.

My wife has converted a substantial amount of our home lighting, as well as our holiday decoration lighting, to LED bulbs. Despite all this investment, I have yet to experience the primary benefit of long life. This made me sit down recently and ask myself why.

As it turns out, the answer is quite simple. The lifetime is not a function of the LED, but rather the total circuit solution.

Figure 1 shows the schematic for an incandescent light bulb. As I once read in a college textbook, the analysis of this circuit is left to the reader.

Contrast the Figure 1 schematic with the Figure 2 schematic that shows an offline LED lamp schematic minus the LEDs. As I'll show soon, there is no need to analyze the Figure 2 circuit operation.

Figure 1

Figure 2

To estimate the failure probability of an electrical circuit, one can apply the product rule for probabilities. Essentially, the rule is that the overall probability of failure is a product of the individual, uncorrelated failures.

Notice that the Figure 1 circuit has one circuit element. Let's assume the probability of failure for a circuit element is 100 ppm. After all, we're discussing a 50-cent light bulb, not a \$30,000 car. Applying the product rule, the ppm failure rate for Figure 1 is 0.9999 or 1 out of 10,000 light bulbs.

Next we look at Figure 2. There we have approximately 60 circuit elements. Using the same product rule and 100-ppm failure probability, the failure rate of Figure 2 is 1 out of 167 lamps. Now this is a big deal, but not yet a catastrophe.

After a quick look around my 2,200-sq.-ft. house, I counted about 50 light bulbs. Once again, applying the product rule, the incandescent lamp failure rate inside my house should be about 1 out of 200. And the LED lamp failure rate should be about 1 out of 4! A 25% failure rate is ridiculous for a product that costs \$10 or more and does nothing more than a product that costs 50 cents.

Perhaps a wiser engineer more skilled than I in the area of reliability would take issue with my 100-ppm failure rate. But doesn't it make sense that an offline power controller with nearly 100 components will have a higher failure rate than a system with 1 component? But no one ever talks about that. We are always told to compare the tungsten lifetime of 1,000 hours against the LED lifetime that is claimed equivalent to the lifetime of the family pet, or something close to that.

According to my wife, who is not an engineer, she purchased nine LED lamps for the kitchen and back porch over a period of one year, from three different manufacturers, and paid on average about \$45 each. Out of the nine, and after two years, one by one they all started to fail. As of this blog, seven of the nine are dead.

I did a further reliability analysis on Amazon.com, looking at the ratings for LED lamps. Out of 400 reviews, 25 people gave a popular \$10 LED lamp a rating of one. I started reading through the one-star reviews and virtually everyone who scored the lamp as a one claimed their score was because the lamps failed very quickly.

Even most of the 18 people who scored the lamp a two did so because of failure. I wonder how many of the five-star ratings would still be five stars after two years.

I've been designing LED circuits for years now. My first circuit was for a stadium sized LED TV and more recently battery powered lamps and backlighting for TVs and laptop computers. It would be disingenuous of me to claim that all LED lighting is useless. There are many great applications for LED lighting. But replacing a one-element off line circuit is not one of them.

1. geek
December 23, 2014

@Scott: I recently read about Surface-mount Devices which are a branch of LEDs. What is your opinion on SMDs in terms of their reliability? Do you think they offer a higher value than conventional LEDs?

2. Scott Elder
December 24, 2014

@tzubair,  When it comes to high brightness LEDs such as those used in home lighting, they are all surface mount to keep the thermal resistance low.

3. amrutah
December 24, 2014

Scott,

the Failure in time mentioned is usually for the entire LED along with the circuit and its elements.  So if I buy 10 lamps today they should last the same Power-on-hours otherwise the product rating itself is wrong.

The math that you have shown makes sense as soon as you start adding the elements (un-correlated).

4. samicksha
December 25, 2014

SMD require either a custom PCB for every prototype or the mounting of the SMD upon a pin-leaded carrier.

5. geek
December 25, 2014

“When it comes to high brightness LEDs such as those used in home lighting, they are all surface mount to keep the thermal resistance low.”

@Scott: What I was more interested in knowing was whether this surface-mounting- has also brought about a change in reliability along with keeping the resistance low?

6. nasimson
December 26, 2014

The circuit difference is orders of magnitude more complex. No wonder such high failure probability. 'The BIG Lie' wont be a hidden lie for long, if the performance continues to be such.

7. PCR
December 27, 2014

Scott thanks for the  in detailed  article,  simply you are saying that the LED are not economically compared with the traditional lighting, But from the point of power consumption it is economical and wont it cover the cost of circuit.

8. Scott Elder
December 27, 2014

It only covers the cost if the LED lamp lasts for as long as the claims.  Here's another opinion:  http://www.dailymail.co.uk/news/article-2546363/The-great-LED-lightbulb-rip-One-four-expensive-long-life-bulbs-doesnt-like-long-makers-claim.html

9. Victor Lorenzo
December 27, 2014

There are applications like traffic lights which make extensive use of SMD LEDs mounted over alluminium core PCBs.

10. Netcrawl
December 27, 2014

@Victor, LED-based products are poised to replace legacy lightings in all general lighting applications, LEDs are the most efficient way to turn an electric current into illumination, it use materials that maximize effect. They have extremely long operating lifetimes, low current draw from DC voltage lines, low heat dissipation, tremdous resistance to shock and vibration, and much smaller size than neon and incandescent bulb. LED can also be pulsed at very high swicthing speeds and can be made to turn on and turn off with logic-level voltage signals. LED provides an extremely effective solution, no doubt.

11. Netcrawl
December 27, 2014

@Scott thanks for the link, I believe LED life expentancy depends on fixture types and usage scenario, but in the search for energy-efficient lightings, LEDs have proven to be the most efficient lighting solutions available. Good quality LEDs use at least about 80-85% less energy than traditional incandescent and halogen lamps, and last up to 25 times longer, recent development in LED technology have greatly increased both light output and efficiency.

12. Netcrawl
December 27, 2014

@Scott, In reality, no one really knows how to define the lifespan of an LED, that's because LEDs do not burn out like an incandescent bulb, their brightness slowly fades. If the lifespan of LED is listed at 25,000 hours, that is the point when the bulb will likely be shining at around 70% capacity.

I think its about time that manufacturers need to come up with something good- a system to accurately convey the lifespan of their products to incandescent and CFL converts.

13. Scott Elder
December 27, 2014

A traffic light doesn't sell for \$10.

I suspect the electronics built into a traffic light is substantially more robust than a light bulb for your house.  My understanding is that one bulb cost nearly \$100 for a traffic light.  And then what does the power conditioning cost?

14. Scott Elder
December 27, 2014

<

If they did that, no one would buy them.

15. Victor Lorenzo
December 28, 2014

@Scott >> “I suspect the electronics built into a traffic light is substantially more robust than a light bulb for your house

A couple of months ago there was a lightning strike in a communications tower a few meters from my home (around 50-to-80 meters). There was a momentary mains power failure and the traffic lights did not recover. The lights in the signals were able to withstand the transcients but the timing and control system in the cabinet crossing the street did not and the operator changed several CPU and I/O boards from the cabinet.

The lights in the semaphore have arrays of high brightness low power LEDs (red, green and yellow) with surge arrestors.

16. Victor Lorenzo
December 28, 2014

@Scott >> “Isn't a traffic light powered by an uninterruptable power supply?

Not in my city, though they use an independent circuit from houses and street lights.

17. Bruce Bailey
December 28, 2014

Scott – The consumer pays more for the LED lamp than an incandescent.  How 'bout the energy costs visible to the consumer (does not include energy cost to manufacture)?  Thoughts? – Bruce

18. Scott Elder
December 28, 2014

Well Bruce,  “Visible” is a big word.  If one goes to the store, buys one LED lightbulb, and has to immediately pay, say, \$12 rather than \$1, I think a consumer feels that penalty immediately.

When you screw in your new LED light bulb, things aren't too exciting.  Might even be a bit disappointing if the purchaser doesn't understand things like color temperature (i.e. nice warm light becomes slightly blue light).  If one is still thinking about the purchase one month later when the electricity bill arrives, perhaps one will notice the \$1 savings.

Where I live, it gets very hot in the summer.  The electric bill is so high (for AC) I would NEVER notice a \$1 savings.  I wouldn't even notice a \$10 savings for 10 light bulbs.

To actually see the energy savings one would need to audit their utility bills over one year to see the difference.  I don't think most people do this.  In other words, the visibility of energy costs is probably not realized by a consumer.  In fact, that is why most businesses would like their customers to pay over time (i.e. TV subscription, club membership, etc.); the bill is small per month and no one pays close attention.

What about a city?  With lots of traffic lights and street lights?  And one employee whose job it is to track the savings?  Sure.  They'll feel the savings because its their job and the bill has lots of zeros.

19. uchiha
December 28, 2014

@Netcrawl : LEDs are semiconductors that efficiently generate light, and require electronic drivers. In a well-designed fixture,the driver is a critical component, managing the power delivery and playing a vital role in overall energy efficiency of a fixture. It is a key element in fixture power consumption per lumen delivered, heat generation, and longer fixture lifetimes

20. uchiha
December 28, 2014

@Bruce : Because intelligent LEDs are dramatically more energy efficient than fluorescents or even plain LEDs, not only are they more cost-effective in current terms, but an imperative in a rising-energy-cost environment. As a result, many industrial organizations are no longer willing to trade off marginally shorter initial payback periods—usually measured in months, not years—for a decade or more of substantially higher energy costs.

21. uchiha
December 28, 2014

@Netcrawl : During the usable lifetime of an LED, which generally exceeds 50,000+ operating (or “on”) hours (or more than twice the lifetime of a traditional light source), it is extremely unlikely that a driver or any other component part would need to be replaced.

22. uchiha
December 28, 2014

investigations into the effect of short-wavelength radiation be it on humans or artwork—suggest that LEDs are dangerous because they emit more blue light than other sources like incandescent bulbs or CFLs.

23. amrutah
December 29, 2014

“I think its about time that manufacturers need to come up with something good- a system to accurately convey the lifespan of their products to incandescent and CFL converts.”

@Netcrawl: Thanks for sharing the info.  Since LED is a semiconductor junction, I think the life span should be measurable in terms of POH, and current limits to turn on the junction.  I still think the life-span measurement that you mentioned is still good.   The only thing that comes to my mind is to improve the semiconductor technology that has 50K POH and bulb shining brightly at 60% current.

Di you think the measurement system has to be improved or the technology?

24. amrutah
December 29, 2014

Just to add on to Netcrawl,

One of the important thing w.r.t CFL and LED's are they emit less of heat.  Given the weightage on the climate change, the heat emited from LED's is less compared to the incandescent bulbs, which is a step forward.  The next thing is to bring the LED costs low and increase the life span and efficiency.

25. PCR
December 29, 2014

Scott thanks for link for the article
It's make a sense……………………

26. PCR
December 29, 2014

Netcrawl, I also thought that way, cause that I have change my lighting solution to the LED few months back and I feels that I have reduce 30% from my total electricity bill. But I am not sure about the life time…

27. PCR
December 29, 2014

It's a great question Bruce. If it consume more energy when manufacturing than a traditional lighting bulbs, actually there won't be a energy savings thou it reduce the individual energy consumptions.

28. Netcrawl
December 29, 2014

@amrutah thanks for that, a primary cause of lumen depreciation is heat generated at the LED junction, LEDs do not emit heat as infrared radiation like other light sources. So the heat must be revomed from the device by conduction or convection, I think thermal management is the most imporatnt aspect of successful LED design.

you're right about the next big thing about LED. LEDs offer the potential for cutting general lighting energy use in nearly half, saving energy consumption and carbon footprints in the process. LED's unique characteristics-including compact size, long life span and ease maintenance, resistance to breakage and vibration, good performance in cold temperature, lack of infrared or ultraviolet emissions, and instant-on performance- are benefical in today's lighting applications. Energy performance of LED products continues to improve rapidly, the US DOE's long-term research and devlopment goal calls for cost-effective warm-white LED packages producing 224 lumens per watt by the year 2025.

29. Netcrawl
December 29, 2014

@Ranasinghe, unlike other light sources, LEDs don't burn out, instead they get progressively dimmer over time (lumen depreciation). LED useful lifetime is typically based on the number of operating hours until the LED is emitting 70 percent of its initial light output, good-quality LEDs in well-designed fixtures are expected to have a useful life of 30,000 to 50,000 hours. A typical incandescent lamp lasts about 1,000 hours, while CFL lasts about 8,000 to 10,000 hours and a comparable flourescent lamp can last more than 30,000 hours. Long life has been billed as a key advantage of LEDs, but understanding how LED products fail and how long they last can be challenging.

30. amrutah
December 30, 2014

By using the LED we are reducing the energy consumption, reducing the emissions, but other question related to this what about the cost of energy generation?, cost of manufacturing a LED bulb Vs. Incandescent Bulb?

This blog has answered the later question.  But the former question still remains to be solved.

Few days back I had seen a TED talk by Bill Gates about CO2 emissions and power generation.  I think it is worth watching this video in this regard.

#### Innovating to zero!                                                                                   http://www.ted.com/talks/bill_gates?language=en

31. samicksha
December 30, 2014

I agree your point @Netcrawl, one of the fact is LED performance is temperature dependent, output is good at lower temp.

32. nasimson
December 31, 2014

> I also thought that way, cause that I have change my lighting solution to the
> LED few months back and I feels that I have reduce 30% from my total electricity bill.

30% is significant. Is it standard or does it vary? As for the lifetime, doesnt it come with the warranty of a few years?

33. Sachin
December 31, 2014

The next thing is to bring the LED costs low and increase the life span and efficiency.

@amrutah, I think life span of LED is not an issue. I think they are very reliable. But cost factor is a concern and yes definitely we need to bring the cost of the LED.

34. Sachin
December 31, 2014

I think thermal management is the most imporatnt aspect of successful LED design.

@Netcrawl, thanks a lot sharing this info. I never knew thermal management was the most important aspect in LED design. I am curiosus to know what steps do we take to mitigate the thermal impact ?

35. Sachin
December 31, 2014

Few days back I had seen a TED talk by Bill Gates about CO2  emissions and power generation.  I think it is worth watching this video in this regard.

@amrutah, thanks a lot for sharing the link. Very informative. It would be very interesting to compare the cost of manufacturing a LED bulb Vs incadescent bulb.

36. Netcrawl
December 31, 2014

@SachinEE thermal management of LEDs is a crucial area of research and development and its highly necessary to keep junction tenperature below 120 C to run the LED's for maximum lifetime, in order to maintain a low junction temperature to keep good performance, every method of removing heat from LEDs should be considered. If the heat is not removed or reduced, the LEDs run at high temperature which is not only lower the LED's efficiency but also makes LEDs less reliable.

37. Davidled
January 2, 2015

LED traffic lighting could be implemented with timer and microcontroller in the board. Red, Green, and Yellow color LED might turn on and off by switching type relay in the board.

38. Victor Lorenzo
January 3, 2015

@DaeJ >> “LED traffic lighting could be implemented with timer and microcontroller in the board

Traffic lights have the indicators and the controllers. The indicators are relatively simple (light bulb or LED w/ driver) and act as slaves. Some controllers are extremely simple and include a couple timers and some logic components for implementing a states machine. Other controllers are much more complex and include a local PLC/microcontroller with remote communication and control interfaces for centralized control by the city traffic authorities.

39. Davidled
January 3, 2015

LED emits more blue light, causing the people to loss appetite that they might loss weight. I am wondering what type dangerous LED might produce.

40. paulfl
January 6, 2015

A Scandinavian colleague bemoaned the compulsion to change to energy-efficient light bulbs; he pays five times the price, has no benefit in the light summer months (they're off)and in the dark, cold winter has to pay more for heating fuel for his 80% efficient boiler. His incandescent bulbs converted electricity to needed heat and light at 100% efficiency, had unity power factor, no EMI, were simple and lasted years.

41. uchiha
January 7, 2015

@Daej : Blue light has a dark side and it is bad for the health. Go through this link. you can get an idea.

42. SebastienA
January 11, 2015

@Scott Elder, so I'm curious; have you taken apart any of these LED lamps and performed a root cause failure analysis?  I'd be curious to know which elements in the circuit failed and why.  For example, is an integrated semiconductor device at fault?  Did the dead parts fail as a consequence of excessively high local temperatures, or was there inadequate protection from mains surges and voltage spikes on the line?

43. Scott Elder
January 12, 2015

@SebastienA, I did not do a root cause analysis.  But there were multiple failure signatures such as flickering LEDs before total failure, flash out where failure occurred upon turning on the wall switch.

I did try to move the bulbs around thinking that the socket contacts might have failed, but this didn't make a difference.

44. boblespam
January 14, 2015

Scott, as I said on another blog were your article is also published, it's really a pitty that with your level of education you still mix and compare two completely different magnitudes with differents units thare a not comparable.

When you mix failure rate (ppm) which is a probability and lifetime (hours) which is a time, you're wrong and your number crunching won't make it right.

For example, good old candle has a failure rate close to zero (once lit, it won't fail in normal conditions) but it has a very previsible lifetime of a few hours: once all the candle wax is burned, it dies.

A LED bulb has a much higher failure rate than the candle because it contains many more components, solder joints and stuff like that. But the same LED bulb has a lifetime EXPECTANCY of 10K hours when accordingly designed.

You can compare ppm to ppm's. You may compare lifetime to lifetime. But you can't compare ppm's to lifetime !

Back to the subject: a standard (Edison) light bulb is more like the candle: very simple in design, but with relative short lifetime.

What you just found is that bad engineered electronic products fail faster than a simple product with decades of engineering and optimization behind them: a standard light bulb is very robust because it has 100 year of development and optimization behind it. Nobody can lie on the box printings about its lifetime expectancy anymore because everybody knows it more or less.

A LED bulb is quite new compared to the Edison bulb and it's quite easy to mislead the customers about it. But I wouldn't expect that someone like you would fall into it: the lifetime expectancy of the LED bulb is not the lifetime of the LED chips built in ! (and it has nothing to do with failure rate)

If you look carefully, on low cost LED bulbs, the manufacturer/distributor won't undetake any kind of lifetime prognosis. If you buy a good LED bulb from a good manufacturer who engages himself about the bulb lifetime (garanteed lifetime), then you can expect that it will last the given lifetime. Because if it doesn't, you may just send it back to the shop and ask for a free replacement !

So there's no LED lie there, just marketting.

What failed in your low cost LED bulbs are probably a simple capacitor, not the LED chip. A chemical capacitors has a pretty good failure rate (ppm) but a short lifetime (hours) when it's used at a voltage close to its maximum specified voltage. There again you must carefully understand the difference between lifetime and failure rate.

Better quality LED bulbs will have capacitors with higher voltage margin so they will last much longer and will better handle the mains surges. They also have a larger aluminium heatsink and a better efficiency so they self-heat less which is also good for the lifetime expectancy of the whole electronic product.

45. nasimson
January 15, 2015

@Paulfl:

Your Scandinavian case study is an unexpected one. Does it mean that LEDs will have little appeal to countries near Pole like NewZealand, Norway, Sweden, Denmark, Iceland, North Canada?

46. Davidled
January 17, 2015

Adding more feature of LED causes the circuit to be more complex unfortunately, even though some kinds of IC are used. Two aspects might be addressed. First, end of line testing process is among the most important ways of evaluating the circuit before releasing the LED product. Second, the designed circuit needs to be analyzed by systematic procedure from engineer. Each function block of circuit could be evaluated in the testing bench.

47. Scott Elder
January 17, 2015

@paulfl,  That's an interesting perspective; 100% = heat + light.  Great insight.

48. paulfl
January 19, 2015

@nasimon The comment was a little tongue-in-cheek but it's a real statement from my colleague Lars in Sweden. Of course in hot areas the opposite is true, not only is the excess heat from incandescents undesirable but the local air conditioning has to work harder to compensate, converting yet more electrical power to cooling and waste heat at way less than 100% efficiency. However the locals still have hot showers and boil kettles so again, generating heat is not in itself a bad thing, it's how you can use it to best effect.

49. amrutah
January 20, 2015

Netcrawl:  I have a question.

If we want to reduce the temperature of the diode junction, we have to control the current through the junction.  Lesser the current, the activity in the junction is reduced and can counter the temperature.  But the intensity of the LED light is directly proportional to the current through the junction.  These are contradicting or conflicting .  What do you say about this?

Does making small LEDs and increasing the LED density help (with each LED taking consuming less current)?

50. amrutah
January 20, 2015

“Did the dead parts fail as a consequence of excessively high local temperatures, or was there inadequate protection from mains surges and voltage spikes on the line?”

@SebastienA: What you are asking is about the practical and it makes sense to question these.  But what I see from the blog is the mathematics behind it.  The probability of Failure is increasing once the # of circuit component increase as in case of the LED's compared to the filament of the incandescent bulbs.

51. amrutah
January 20, 2015

@Scott and @paulfl:

Thanks, this is nice and interesting (the Heat+light).  But controlling/balancing the 2 components is important and difficult.  What do you think about the effect of this on green energy?

52. NBR32
February 3, 2020

Everyone mentions how LED lights are energy saving. I’m clearly not seeing this. As a matter of fact a 6 months back I replaced every light bulb in my home to a LED light bulb and noticed an increase of usage of lighting on my monthly energy usage. I haven’t changed my usage with these lights compared to my prior incandescent light bulbs. Actually I am more prone to turning them off more frequently than B.I.(before incandescent) due to LED lights seems to generate headaches and seems to strain my eyes causing many out of focus blurring. Minor blurring but enough to concentrate more to refocus on words. My usage is now for these LED lights is now at 35% of cost on my bill which has now become my #1 energy consumption. #2 is kitchen at 19%, #3 is electronics at 16%, #4 is heating at 13% which I have a gas furnace, #5 being laundry at 9% and other being #6 at 8% in December 2019. Compared to the year prior 2018 in December my usage of lights was #3 using all incandescent lights. That’s with leaving lights on more often when leaving a room than now. These LED lights were giving to me by the utility company I use to help me on saving energy and cutting my costs down. Which is obviously horse shit. Luckily I’ve stocked piled up on incandescents back when a Hitler wanna be was our president banning the manufacturing and sales of them in the US. So now I’m throwing out all of my led light bulbs and putting back my more energy conserving cost saving incandescent bulbs back to lighting my home. I also never understood how everyone says LED burn cooler. Possibly degree wise but LED bulbs get pretty damn hot especially near the base of it. Also when comparing both types of light bulbs with my electromagnetic meter, a fairly good one that wasn’t cheap, it is evident that LED lighting puts out a much, much higher field than a incandescent which has been proven by folks in white lab coats to be a health risk on a cellular level. So now I know the picture on these LED lights has a much bigger picture than the lies and deception on being forced to use these lights. I knew then without thought when Obama spoke of this lighting situation I needed to stock up and glad I did.

• Comfortable
February 3, 2020

Incidentally, the US DOE light standard changes that all but eliminated incandescent lighting have been rolled back since about 1 month ago. Look here: https://earther.gizmodo.com/trump-wages-war-against-the-true-enemy-of-the-state-le-1840611817. You should be able to replace your LED lights for the foreseeable future.

Also, with regards to LED lights causing health issues; it is well known that when LED lights are pulse-width-modulated (for dimming) below about 400Hz, certain people can experience adverse health problems. For example, in some cases epileptic seizures can be induced. Most LED lights that are dimmed, are dimmed near 120Hz or so. That is the point of detection for the average human. It is entirely possible that your eye strain and headaches are a result of LED dimming.

Even if you don’t dim your LEDs, the power supplies don’t filter out all the line frequency ripple. So there are still 60Hz harmonics present (i.e. 120Hz, 180Hz, ….).

Prices have dropped substantially since I first wrote the article. I have since found one valuable reason to use LED lights. Namely, I place them in the light fixture above my work desk because the light color can be white rather than a warmer color, and I can place the equivalent of 200W of incandescent lighting about 2 meters from my head without the incandescent heating.

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