The life expectancy of an LED is generally speaking somewhere around 50 000h to 100 000h. However, this answer can be a bit misleading, because there are a fair amount of factors that are not taken into consideration when calculating this number.
In optimal conditions, it is entirely possible for LED-based lighting to last well over 100 000 hours. LEDs only get dimmer with time and they don’t “blow” like traditional bulbs which means that they are capable of lasting longer than the driver that provides them with power lasts.
Following this, here we will take a look at how long an LED will actually last.
Defining When an LED Chip Counts as “Dead“
Before we start taking a look at different things that can affect the lifetime of an LED, we first need to clearly identify when an LED is considered “dead“ or out of function. For any other light source, you would simply say that it’s dead when it’s not emitting light anymore, but that definition doesn’t quite work as well for LEDs.
The reason for this is that LEDs rarely ever fully die out like other light sources. This is because an LED doesn’t have anything that really “wears out“ in the same way that other light sources do.
For example, a regular old incandescent bulb has a tungsten thread that eventually will wear out and burn off, which causes the bulb to stop emitting light. Contrary to this, an LED doesn’t have anything that would cause a similar effect due to the way it is constructed.
What happens with an LED instead is that it starts to simply grow dimmer and dimmer the longer it stays alive. This is why it is important to actually define what constitutes it being “dead“ because an LED can actually last a very long time before it actually fully dies out.
So why exactly is this factor not mentioned in calculating an LED’s lifespan? Well, it is, it’s just that the manufacturers have a tendency to undershoot the lifespan in their specifications.
This is for the same reason that a lot of foods’ expiration dates aren’t always accurate either, because they only mark it for a time they can guarantee that it will be good.
This explains why an LED marked as 50 000h could definitely last up to and even more than 100 000h, because they are actually capable of those numbers but simply just not marked as it for the purpose of their specifications being accurate.
How LED Manufacturers Measure The Lifespan Of LEDs
Now that we have established that the actual lifetime of an LED can be way longer than the time given in the specifications, how exactly do the manufacturers go about calculating this number?
Normally for any sort of light source, you would simply leave it on and document when it breaks, but that doesn’t quite work for LEDs. This is partially for the reason mentioned above, but it’s more because of the amount of time it actually takes for an LED to burn out.
If we imagine that it would take 100 000h for an LED to burn out, you would need to leave it on 24/7 for about 11.5 years. That is simply too much time required to test the products, so therefore they need to make a reasonable assumption of its lifespan even though it (in most cases) won’t have lived for very long.
This type of testing also wouldn’t work for the factor of the product’s relevancy. Creating better and more energy-efficient light sources has been a very hot topic in the past couple of decades, meaning that product development happens extremely fast.
The effect of this is that testing products for 10+ years would mean that the tested product would be severely outdated by the time it would actually hit the shelves.
How Manufacturers Label LEDs Lifespan (LLMF)
In order for us to make anything conclusive out of how long an LED will actually last, we need to take a look at how the manufacturers label their LEDs
One common system used to label the LED’s lifespan is LLMF, which is an acronym that stands for “Lamp Lumen Maintenance Factor“.
What this labelling does is that it simply describes how much of the originating lumen (light output) is maintained in the diodes after a specific time. This gives you the option to see what the general natural decay looks like for an LED.
So what exactly does an LLMF label look like? Something labelled with this system will have a label on it that looks something like this;
- L80B20 50 000h.
- L70B10 100 000h.
- L80B15 100 000h.
To put this in the simplest terms possible, the L number means how much % of the lumen remains in the LED after the specified time, which defines the meaning of LLMF itself.
The B value represents the percentage of how many fixtures of this same kind are expected to not hold up to the L value. Essentially it means that it describes how many % of them are expected to fail the prescribed L value.
So if we have the label L80B20 at 50 000h on a fixture that normally produces 1000 lumen, that would mean that after the 50 000h have passed the fixture will still have retained at least 80% of its original lumen amount. Since we specified that this fixture normally produces 1000, this would mean that the LED would still emit at least 800 lumens.
In order to fully understand what the B value means we would need to have multiple fixtures, so in this case, we will imagine that we have 10 of them.
If we have B20 then that means that after the 50 000 hours are up we should expect a maximum of 20% of the fixtures to not hold up to the L80 standard we previously established. In order to get a more detailed and in-depth explanation of this concept, you can go here.
One thing worth noting here is that the number L70 is very common in this system, a lot of luminaires will be labelled with L70 over any other number. This is because it is a threshold for when we humans can actually determine a change in light level when the difference exceeds 30%.
Outside Factors That Affect LED Lifespan
While most of the factors that determine a LED’s lifespan are due to its construction, there are several factors outside of that which also can determine its lifespan which we are going to take a look at.
The temperature of the LED’s surroundings is a very important factor when you look at its lifetime. This is because LED, just like any other electronic device, performs worse in heat.
While LEDs don’t produce much heat themselves, they still start dying off at a way faster rate if the surrounding environment is hot rather than cool.
This is because the higher the junction temperatures are in an LED the faster it degrades, which is why in an ideal world you would want to keep them at around 25 degrees celsius in order for it to reach its maximum lifespan.
The LEDs driver is a factor that is quite often overlooked. The driver is the electrical component that translates the power from your outlet into power that the LED luminaire actually can handle and produce light from.
These drivers work great and do their job perfectly, however, there is a problem we run into when we discuss the lifetime of LEDs. This is because the lifetime of the actual driver in itself can be a bottleneck in testing this statistic.
A regular driver has a life expectancy of around 25000h, which is far less than the actual LED itself. There isn’t exactly much that can be done about this except for replacing the driver when it fails, unfortunately.
Another overlooked factor is the fact that LEDs (or any light source for that matter) lose out on lumen output simply for being a bit dirty.
Seeing as you measure LEDs’ lifespan by how much they fall off, it can give a false impression that the LED is going bad when in reality it’s just a bit dusty.
In fact, in the LLMF descriptions, it is actually specifically accounted for that the light source needs to be cleaned off about twice a year in order to retain its expected lumen output.
The cleaning of these probably doesn’t happen as much as it should in the real world, but it is something that should be taken into consideration if we want to reach the very optimal levels of life.
So what exactly can we conclude from this? With all the information above, we can conclude that an average LED most likely is able to last far longer than its prescribed lifespan.
As previously mentioned we can’t exactly test that though because of how long it would actually take, but we can make an educated guess in saying that the current LED technology is probably capable of lifespans well over 150 000h.
However, the actual driver is most likely not going to be able to keep up with this and will be in need of replacements a few times during the lifetime of the LED.