Invented by Nick Holonyak in 1962, LEDs are one of the most exciting lighting technologies to emerge in the last century. Promising a safe, low-cost and ultra-efficient alternative to traditional bulbs, LED lights are now experiencing their fastest ever growth in market share. One primary feature of the LED is its long life expectancy: it’s often tipped as having a potential lifespan of up to 10 years per bulb. Problem is: real-world tests have shown almost 30% of the bulbs (66 of 230 bulbs) actually failed long before this.
So, why are some LED lights struggling to reach their maximum potential age?
Before we pin the blame on ineffective technology or the international light bulb conspiracy, let's review the facts to better understand the true life expectancy of LED lights.
How is LED life expectancy measured?
One of the key issues in determining how long LED light bulbs last is how they are measured.
The lifespan of traditional incandescent bulbs is calculated quite simply. It’s referred to as Average Rated Life (ARL), which is the length of time it would take for 50% of the sampled bulbs to fail completely (an average of 1,000 hours for traditional bulbs).
The lifespan of the modern LED, on the other hand, is measured differently.
That’s because LED lights rarely fail completely as traditional bulbs do. Generally speaking, their luminosity will fade gradually over time.
So LED lifespan needs to be calculated in a less binary way, leading manufacturers to define it as the point at which luminosity has reached 70% of initial output. This measurement is usually expressed as B50-L70, which is shorthand for the time that 50% of LED bulbs in ideal conditions will have 70% of their rated output.
However, unlike traditional bulbs that end up at a single maximum figure of 1000 hours, the B50-L70 of LEDs ends up as anywhere between 10,000-50,000 hours.
Every LED will have an L70 rating, which is usually calculated in hours. For example, an LED bollard with L70 of 50,000 will - in 50% of all cases - have a rated lifespan of 50,000 hours, at which point they will emit 70% of their original output. If an LED has L50 of 50,000 hours, its output decays faster than one with L70 of 50,000 hours, and so on.
So, what causes such a large discrepancy in LED life expectancy? To answer this point, we first need to look at what causes LED lights to fail.
Factors impacting the life expectancy of LED lights
When an incandescent bulb fails, it's immediately visible why: the filament, quite simply, breaks and the bulb turns off.
LEDs, on the other hand, emit energy as light of varying intensity and color when a current pushes electrons through various materials. So, rather than having binary on-off failures, LED bulbs decay gradually as defects in these materials occur.
Let’s hone in on these potential failure points in more detail.
Within an LED there is an ‘active region’, where a process called radiative recombination occurs and light is produced. If the material used in this active region has an existing defect, it will be worsened by heat and electric current. Eventually, this leads to a decay in the output of the LED.
This issue is avoidable if the manufacturer chooses an LED which will exceed the expected lifespan of other components used within the bulb itself.
In order to maximize the length of time that the LED lights you buy last, check the LED component choice on the bulb’s datasheet to be sure that it’s of a high enough quality.
Electrical Over Stress
"Electrical Over Stress" (EOS) is caused when an LED receives more power than its recommended maximum. This can be caused by human error, faulty power supplies, bad PCB layout or faulty components within the LED bulb assembly.
One cause of EOS is a static discharge making contact with the LED during the manufacturing, shipping or handling of the component. Many manufacturers will protect against this type of EOS by including a static suppressor, which will absorb radio frequencies that would otherwise damage the LED. EOS can also be caused by a power supply spiking and rippling. This can occur through poor design or an inappropriate driver which cannot regulate it's output consistently, leading to a surge in voltage when the LED is turned on. It can also happen during the testing process when LEDs are connected and disconnected rapidly.
EOS can be largely prevented by using protection circuits within the thermal and electrical parts of an LED system. Protection circuits work by regulating the maximum voltage that an LED receives, a bit like a traditional fuse. A protection circuit will kick in once a specific limit is exceeded, and will then reset after the fault clears.
Most well-designed LED systems from major manufacturers include these, with creative solutions like 'soft-start'.
You may have noticed, for example, that some LEDs bulbs take a few moments to turn on. This is designed to reduce the activation spike and increase the lifespan of the LED.
LEDs run much cooler than its competitors but still produce a small amount of heat within their diode. In fact, excessive heat has been found to reduce the lifespan of a LED, making it important to be aware of how LED lights are affected by hot temperatures.
In short, semiconductors and capacitors are both prone to failure under heat stress making it really important to consider the LEDs operating temperature range when shopping for LED lights.
The best performing bulbs are designed to reduce heat stress to protect these heat-sensitive components and increase the lifespan of the bulb. First, non-LED components are mounted separately to the heat-sensitive LEDs. Second, capacitors are designed to operate at higher temperatures.
As electricians, there are two practical tips you can apply to increase the lifespan of LEDs.
- If you are installing LEDs, choose appropriately sized luminaires and ensure LED bulbs are ventilated to allow heat to escape.
- When purchasing an LED, look at the LED enclosure and heatsink. A well-designed LED bulb should have an effective heatsink with gaps between the fins to allow heat to dissipate into the air.
So, how long do LED light bulbs really last?
Unfortunately, there is no simple answer to this question.
The lifespan of LED light bulbs depends on several key factors, but generally speaking the range is anywhere between 10,000-50,000 hours.
That’s a big range, but it means that your LED bulb could last up to 10 years, depending on how extensively it’s used and the conditions it’s used in.
While we can’t definitively say how long a bulb will last for, LED bulbs are still much longer-lasting than their traditional counterparts, as seen in the table below.
To maximize the lifespan of the LED bulbs you install, be sure to watch for:
- Components: Choose LED bulbs with good component choices and install with appropriate power supplies. If your LED bulbs are short-lived, check your light fitting for variations in voltages.
- Environment: Install LED bulbs in appropriate environments with good ventilation to allow cooling. Try to avoid installing near sources of heat.
LED bulbs are fairly complex little pieces of technology, so it makes sense to invest in the highest quality products from LED manufacturers with a proven record. Do this, and you’ll be sure to install a lighting solution that will stand the test of time.