How LED Bulb Lifetime Is Rated

How LED Bulb Lifetime is RatedLEDs are a hit with facility operators because they’re energy-efficient and long-lasting. Unlike incandescent or fluorescent lights, they don’t make a popping noise and die suddenly, unless the components fail. Instead, their light output slowly declines over time.

But not all LEDs are created equal. LED lifetime varies for each fixture. And after they’re installed, various factors can decrease that lifetime. Here, we’ll walk you through how manufacturers rate the lifetime of your LED lights and explain several issues that could shorten that lifetime.

How LED Bulb Lifetime Is Rated

Let’s start by discussing the lifetime of an LED. The Illuminating Engineering Society of North America (IES) published three documents that help quantify and calculate the life expectancy of an LED lamp or fixture.


This document, Lighting Methodology (LM) Number 80, sets out the process for testing LED chips for longevity. This information, while highly technical and expansive, may help the specifier understand the quality of the chips selected by the LED lamp or fixture producer.

Basically, the chip maker test process includes testing a quantity of LED chips for 6,000 hours at three different temperatures, typically:

  • 25 C°
  • 35 C°
  • 55 C°


This document, Technical Memorandum (TM) Number 21, explains the method of extrapolating the LM-80 test data to develop life expectancy and lumen depreciation at a future point in time. Typical life ratings published by industry manufacturers are expressed either as:

  • L70: Life rating in hours when 70% of rated lumens remain (30% lumen depreciation)
  • L80: Life rating in hours when 80% of rated lumens remain (20% lumen depreciation)
  • L90: Life rating in hours when 90% of rated lumens remain (10% lumen depreciation)

As an example, TM-21 might project that LED chips could have a life expectancy of 100,000 hours at L70. Based on operating hours or other ambient variables, say 24/7 (8,760 hours/year), that equates to 11.4 years after 30% lumen depreciation.


The best overall picture and quality of an LED system (chips, driver, heat sink, wiring, assembly, surge suppression, and other components) are determined by the LM-79 report. The LM-79 testing procedure captures performance characteristics and full capabilities of LED as a system (integrated LEDs, luminaries, and lamps). This 13-15 page report, generated by a third-party accredited test laboratory, furnishes output data from multiple tests. It is a snapshot of a “test sample” provided by the manufacturer. The report is a useful benchmark to compare like systems of manufacturer A vs. B vs. C, etc.

The LM-79 report provides:

  • Test parameters and equipment
  • Test temperatures
  • Humidity
  • Electrical characteristics
  • Voltage
  • Wattage
  • Lumens per watt
  • Other electrical or photometric characteristics

When comparing systems, the LM-79 report is crucial to see the big picture of each system being evaluated.

LM-79 reports do not address:

  • Lifetime ratings
  • Changing performance over time
  • LED case temperature


Factors Influencing LED Life Expectancy

Now that we’ve covered LED lifetime, let’s cover what can drastically shorten that lifetime. Most LED system issues are due to driver failure, an essential LED component. Driver failure can be caused by:


Severe heat and solid-state electronics don’t mix. And LEDs are no different. Though most LED lights are designed to withstand heat up to about 180 °F, if your driver hasn’t been correctly designed with heat sinking in mind, it’s easy to overheat, which can shorten its life. This is especially important when working in extreme heat, like in a factory, or even in areas with hot summers or lack of air conditioning.

Heat can also affect LED systems with IR sensors. You probably remember from your school days that heat rises. And in a warehouse environment, higher temperatures at various mounting heights can negatively influence the functionality of infrared sensors controlling LED lighting. The result? The LED lights won’t function as they should — potentially leading to accidents. If this is a problem in your facility, look for a sensor (like a microwave sensor) designed to work in areas with high heat.

Misapplied voltage

Driver failure may be caused by misapplied voltage. If the installer fails to verify the circuit voltage and ensure the LED system voltage is compatible, failure or performance could be impacted. Issues may also arise if the voltage is correct, but the fixture is incorrectly installed.

Voltage surges

A voltage surge can also zap the life from your LED drivers. In areas with frequent power outages or “dirty” power, LED lighting may be more prone to failure. That’s because solid-state lighting is much more sensitive to surges than high-intensity discharge sodium or metal halide. So you’ll probably need to investigate power conditioning at the electrical panel or a higher-rated surge protection device for the fixture.

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Inadequate ingress protection (IP) ratings

Another factor that can alter the lifetime of an LED system is inadequate ingress protection (IP) ratings. This rating is made up of two numbers.

  • The first digit, particulate matter, ranges from 0, no protection against ingress, to 6, the highest protection against ingress.
  • The second digit, moisture, ranges from 0, no protection against moisture, to 9, protection against close-range high-pressure, high-temperature spray, or wash-down. A moisture rating of 1, for example, would be protection against lightly dripping water.

It’s important to specify the correct IP rating for the fixture and the driver. If, for instance, a facility’s sprinklers deploy above the installation, water could destroy the LED’s drivers if they aren’t wet-rated, at least IP65.

Understanding and maximizing the lifespan of LEDs is important for deciding which lights to install in a facility. Turn to tools like the LM-79, LM-80, and TM-21 documents to understand the expected lifetime of your LED fixtures, but know that factors like heat, misapplied voltage, IP ratings, and voltage surges can all shorten that projected lifetime.

Knowing all the factors involved in LED life, having safeguards like efficiently designed drivers with proper heat sinking and surge protection, and planning for unexpected loss of normal power can help you get the most benefit from your LED lights and investment.

Need help choosing the right LED lights for your project? Our Lighting Design Tool has you covered.