Understanding Life Expectancy (L90B5) in Horticultural Lighting

When you’re comparing supplemental lighting solutions for your greenhouse, the life expectancy rating of an LED fixture is one of the most important—but often misunderstood—factors to evaluate. Also known as lamp life, this metric provides insight into how long your lighting investment will maintain its performance, how to plan for maintenance, and ultimately, how to protect your ROI.

Many growers focus on efficiency and total light output, but overlook life expectancy ratings and warranty strength. Yet these two factors determine how consistently your fixtures perform for years to come. Whether you measure your light levels regularly or simply rely on visual cues, understanding fixture age, warranty terms, and design quality will make you far more confident in assessing performance, crop impact, and long-term cost.

It’s also important to recognize that different components within a horticultural lighting fixture have their own individual life ratings—diodes, PCBs, drivers/ballasts, lenses, and even wiring. For this article, we’re focusing on the standardized rating for the entire luminaire, which is what manufacturers use to communicate overall life expectancy and warranty coverage.

What Does L_xB_y Mean? Understanding the Standard

L_xB_y is the global industry standard used to describe the expected depreciation of LED light output over time. This is one of the strongest indicators of long-term quality and reliability in horticultural lighting.

L_x — Light Output Depreciation

“L_x” defines the acceptable percentage of original light output a fixture may decrease to within a specific number of burning hours.

• L90, for example, means the luminaire is expected to maintain 90% of its original intensity—or better—throughout the rated life hours.

B_y — Diode Failure Allowance

“B_y” specifies the maximum percentage of LED diodes allowed to fall below the L_x rating within those same hours.

• B5 means that only 5% of diodes are allowed to fall below the L90 threshold during the rated lifetime.

Put together, an L90B5 rating means the fixture must maintain

• at least 90% of its original light output, and
• no more than 5% of its LEDs can degrade beyond that point within the stated lifetime hours.

Why L90B5 Matters to Growers

Light depreciation affects crop uniformity, production timing, quality, and yield. Even a 5–10% change in PPFD can influence plant morphology, flowering, and overall biomass. General rule of 1% depreciation of light is 1% reduction in photosynthesis equaling 1% reduction in growth and yield.

Research from institutions like Wageningen University & Research and Utah State University consistently shows that plants respond directly to absolute light intensity, not “percent of original output.” In practice, this means:

• As fixtures depreciate, you lose real PPFD on your canopy.
• Without monitoring light levels, growers may unknowingly operate with sub-optimal intensities.
• Lifespan and depreciation directly influence annual operating costs and re-investment cycles.

A high life expectancy rating isn’t just about durability—it’s a direct driver of crop performance and predictability.

P.L. Light Systems’ L90B5 Rating: The Best in the Industry

Every P.L. Light Systems LED horticultural fixture is rated L90B5—meaning your fixtures are engineered to maintain exceptional output and quality over their complete warranty period.

If more than 5% of diodes fall below 90% of original output within the rated hours, your fixture qualifies for repair or replacement under warranty.

By contrast, some manufacturers offer:

• very limited or no warranty at all
• only diode-level warranties (not the entire luminaire)
• lower L_xB_y ratings (L90B10, L90B50, etc.) where 10% or 50% of your diodes could fall below the 90% output and not be covered by warranty!
• no standardized testing data

This leaves growers exposed to risk, inconsistent lighting, and unexpected replacement costs.

A strong life expectancy rating is one of the clearest indicators that a fixture is built for commercial greenhouse realities—heat, humidity, dust, chemicals, and mechanical stress.

How P.L. Light Systems Achieves Greater Life Expectancy

Many lighting manufacturers try to showcase high efficiency numbers (and reduce product costs) by using fewer diodes, each driven near 100% or higher output. While this may initially produce strong efficiency specs, it places significant stress on:

• the diodes
• the printed circuit board assembly (PCBA)
• thermal systems
• electrical components

Running diodes at max current accelerates depreciation through:

• electrical stress
• increased heat
• electrostatic damage
• faster spectral shift
• uneven line loss across the board

Our Engineering Approach: Underdriving More Diodes

P.L. Light Systems takes a different—and more robust—engineering approach:
a higher density of diodes operated at a lower current (underdriven).

This delivers several advantages:

• Better longevity: reduced electrical and thermal stress
• Lower heat generation: extending PCB and driver lifespan
• More uniform spectral stability: especially when specific wavelengths degrade at different rates
• More consistent depreciation across the fixture
• Flexible spectral design: more diodes = more controlled spectral mixing
• Stronger life expectancy ratings: enabling L90B5 performance

How Growers Can Extend the Life Expectancy of Their Fixtures

Even a well-engineered fixture relies on proper care to perform at its best. Regular maintenance helps preserve output, reduce heat buildup, prevent damage, and maintain transmissibility through the optical lens.

1. Maintain and Clean Fixture Components

Dirt, dust, and condensate reduce light output and trap heat inside the fixture. This accelerates diode and driver degradation.

To clean your fixtures safely and effectively:

• Fully disconnect or unmount the fixture before cleaning
• Use cleaning vinegar, distilled water, and a microfiber cloth
• Avoid harsh chemicals or high-pressure sprays
  • Approved chemical list available in our LED Maintenance Guide
• Follow our Maintenance Guides and instructional video

(Watch the full cleaning guide here: https://youtu.be/WrC9X2EuCy0?si=Qf0cPE6E6SDpcswA)

2. Protect Fixtures During Greenhouse Cleaning and Maintenance

Water, chemicals, and debris are the most common causes of fixture damage.

To prevent issues:

• Disconnect fixtures from main power
• Bag each fixture with at least a water-repellent barrier
• Seal the bag tightly around the cable ingress
• Maintain a “drip loop” so fluids don’t travel down cabling into the connector
• Choose your protection method based on scale—individual unplugging or power shutoff

Watch the greenhouse cleaning with bagged fixtures video here: https://www.youtube.com/shorts/5M5FGVI4Hco 

These small precautions can significantly extend fixture lifespan.

Measure Light Levels to Monitor Degradation Over Time

You can’t know how your fixtures are performing unless you measure them.

Regular PPFD measurements allow you to:

• track depreciation
• plan maintenance
• validate warranty conditions
• maintain crop uniformity
• optimize seasonal light strategies

Reliable measurement requires a quantum PAR sensor or spectrometer that measures µmol/m²/s, not W/m². Since only ~45% of solar radiation falls within the PAR range, using the wrong tool leads to inaccurate conclusions.

Protecting Your Investment Starts With a Strong Warranty

P.L. Light Systems offers one of the most comprehensive warranties in the horticultural lighting industry—supported by real testing, transparent engineering practices, and an L90B5 life expectancy rating that growers can trust.

By properly maintaining your fixtures and regularly measuring light levels, you can ensure optimal performance and protect your investment for years to come.

For more information on fixture life expectancy, maintenance practices, or warranty details, connect with our team: info@pllight.com