What is Lumen Maintenance, How is It Measured, and Is It Time for You to Replace Your LED Lighting?

LiteSource  |  April 17, 2025  |  Agency News

When LEDs first entered the commercial and residential lighting markets, the long lifespan was an immediate selling point. Unlike incandescent bulbs that fail suddenly, LED fixtures gradually lose brightness over time. This phenomenon is measured as “lumen maintenance,” and understanding it can help you plan for the eventual replacement of your LED fixtures—often referred to as an LED-to-LED conversion.

In this post, we’ll break down:

  • What lumen maintenance is and why it matters
  • How ratings such as LM-80 fit into the conversation
  • Why it might be time to think about upgrading older LED fixtures to newer, more efficient options

What Is Lumen Maintenance?

Lumen maintenance is a measure of how well a light source retains its brightness over its operating life. Every light source, whether traditional or LED, loses a portion of its initial brightness as it ages. For LEDs, this dimming process is typically gradual, and they almost never go out in a dramatic “pop” like an incandescent bulb.

Instead, LED fixtures will operate at a reduced level of brightness that’s referred to as lumen depreciation. For example, if an LED fixture starts at 100% brightness, but after ten years of operation is providing only 70% of that original light output, we say it has experienced 30% lumen depreciation. The ability to continue providing a certain threshold of light output (e.g., 70% or 80%) over a given period of time is central to the concept of lumen maintenance.

Key Rating Systems: LM-80 and Beyond

One reason LEDs quickly became so popular is that they are tested under standardized methods that help predict their long-term performance. One of the most recognized test methods is LM-80.

  • LM-80: This test method—developed by the Illuminating Engineering Society (IES)—measures the lumen maintenance of LED light sources over a defined period, typically 6,000 to 10,000 hours or more. When a product’s LM-80 data is available, lighting designers and specifiers can estimate how long an LED will remain above a certain percentage of its initial light output (for example, when it will reach L70, or 70% of its initial brightness).
  • TM-21: Another standard that is often mentioned alongside LM-80 is TM-21. This method takes the LM-80 test data and projects the future lumen maintenance of an LED. In simpler terms, if LM-80 provides the actual data, TM-21 does the math to estimate how long until the LED loses a specified percentage of its brightness.

Understanding these ratings can help end users—and lighting professionals—predict whether an LED product is likely to meet performance expectations over the long term.

 

Planning for LED-to-LED Conversions

The first generation of LED fixtures that replaced incandescent, fluorescent, or high-intensity discharge (HID) lamps have now been in use for about a decade. While they likely performed extremely well, it’s worth considering an upgrade to newer LED technology:

  1. Efficiency: LED efficiency has improved significantly in the last decade. Modern LEDs can deliver more lumens per watt than older fixtures, which translates to energy savings.
  2. Color Selectability (CCT): Selectable CCT (Correlated Color Temperature) LEDs allow you to choose the color temperature—warm to cool—at the time of installation. This flexibility wasn’t always available in older models.
  3. Easy Installation: Many next-generation LEDs are designed with retrofit kits and other modern mounting methods that significantly reduce installation time.
  4. Controls: Today’s LED systems frequently come equipped with smart lighting controls, occupancy sensors, and remote management capabilities. This helps optimize energy usage, cost savings, and user comfort.

Just like all technology, LED fixtures evolve. Planning for an LED-to-LED conversion ensures you’re not caught off-guard when your older LEDs no longer meet your lighting needs.

Why Lumen Maintenance Matters for Replacement Planning

Because LEDs rarely “burn out” entirely, it can be tricky to recognize when it’s truly time to replace them. That’s where lumen maintenance guides your decision:

  • Performance Drop: If spaces seem dimmer than they used to or fail to meet the desired lighting standards (for example, in offices or commercial settings), it might be time to replace those older LEDs.
  • Changing Requirements: Over time, your lighting requirements can change (e.g., a warehouse is repurposed for a more detailed task). Lumen levels you once found acceptable may no longer be sufficient.

Assessing the lumen maintenance of your fixtures—particularly if they’ve been in service for 8-10 years—can help you plan for a smooth upgrade. If you’re nearing or have surpassed the LM-80/TM-21-projected life expectancy, it may be time to consider new LED products.

An Evolving Industry: Staying Ahead of the Curve

LED technology continues to improve. If the LED fixtures installed a decade ago saved you energy and maintenance costs at the time, think about how much more advanced new products have become. The LED industry is constantly pushing boundaries on:

  • Higher efficacy (lumens per watt)
  • Longer rated lifespans (improved lumen maintenance)
  • Simplified retrofitting
  • Enhanced control, automation, and connectivity

While lumen maintenance ensures your lights gradually fade instead of burning out abruptly, don’t let that gradual decline hide the fact that a refresh could significantly improve your environment’s lighting quality, comfort, and energy efficiency.

The Bottom Line

  1. LEDs fade over time, rather than failing suddenly—this is the heart of lumen maintenance.
  2. Understanding test methods like LM-80 helps you gauge the lifespan of LED fixtures.
  3. Plan for LED-to-LED conversions when your fixtures no longer provide sufficient illumination or have passed their projected lumen maintenance threshold.
  4. Modern LED technology is even more efficient, offers adjustable color temperatures, is easy to install, and can integrate with advanced lighting controls.

By keeping an eye on lumen maintenance, you can determine exactly when a space’s lighting has dropped below an acceptable level for your needs. While this post isn’t meant to be a commercial, having a trusted partner to guide your next steps and offer a wide selection of cutting-edge products can be invaluable. Whether you’re a facility manager, a homeowner, or a contractor, paying attention to lumen maintenance ensures you won’t be caught off guard as your LED fixtures age—and you’ll be ready to reap the benefits of the next generation of high-performance, energy-saving LEDs.