How to assess the reliability and lifetime of LED lighting

"50,000 hours": the claim appears on every data sheet, but says almost nothing on its own. The reliability of LED lighting is judged through several precise indicators · L70, L80, B10, MTBF · and through the quality of invisible components such as the driver and thermal management. This article gives you the keys to assessing the real lifetime of a luminaire and recognising a serious supplier.

The lifetime of an LED is not just a matter of failure

Unlike a traditional lamp that "burns out", an LED generally does not go out suddenly: its luminous flux declines gradually over time. The notion of lifetime is therefore based on a threshold of flux maintenance, and not on total failure. That is why we speak of useful life: the point at which the lighting no longer provides enough light for its use, well before it goes out completely. This increased reliability is one of the great achievements of the evolution of LED technology.

L70, L80: maintenance of luminous flux

The Lx notation indicates the percentage of luminous flux maintained after a given number of hours. Thus:

• L70: the duration after which the luminaire still emits at least 70 % of its initial flux.
• L80: the duration after which it maintains at least 80 % of its initial flux · a more demanding criterion.

For example, a luminaire stated as "L80 at 50,000 hours" retains at least 80 % of its flux after 50,000 hours of operation. For the same performance, an L80 is therefore better than an L70: the light stays closer to its original value for longer.

B10: the share of products concerned

The Lx value alone is incomplete: it must be accompanied by a Bxx index, which specifies the proportion of luminaires likely to be already below the threshold. A classification of L80B10 at 50,000 h means that after 50,000 hours, 90 % of the products maintain at least 80 % of their flux, and 10 % have fallen below it. The lower the B figure (B10 rather than B50), the more rigorous the promise. Be wary of an Lx value displayed without Bxx: it does not carry the same weight.

These values are based on standardised measurement protocols. The LM-80 standard measures the flux maintenance of LEDs (typically over 6,000 to 10,000 hours of testing), and the TM-21 method is used to extrapolate lifetime beyond the tested period.

MTBF: reliability of the electronic system

MTBF (Mean Time Between Failures) characterises not the decline in flux but the probability of outright failure of the system, often linked to the power supply electronics. A high MTBF indicates a system designed to operate for a long time without failure. It is an indicator complementary to Lx/Bxx: the first speaks of gradual wear of the light, the second of failures of the device.

Thermal management: the decisive factor

Heat is the number one enemy of the LED. The hotter the LED junction gets, the faster the flux declines and the faster the electronics age. Thermal management · heat sinks, choice of materials, design of the luminaire · is therefore the most structuring factor in real lifetime. The same LED component will last very differently depending on whether it is properly cooled or not. This is also one of the benefits of high luminous efficacy: a high-efficiency luminaire gives off proportionally less heat, as we explain in our article on luminous efficacy and the 200 lm/W luminaire.

The driver: the often underestimated link

The driver (electronic power supply) is frequently the first component to fail in an LED luminaire. Its quality, its tolerance of voltage variations and its own thermal resistance largely determine the reliability of the whole. A driver from a recognised brand, correctly sized and well ventilated, often makes the difference between an installation that keeps its promises and one that multiplies premature replacements. On installations that are difficult to access (great heights, isolated sites), this point becomes critical because every intervention is costly.

IP and IK: withstanding the environment

Reliability also depends on how well the luminaire suits its environment. Two key ratings:

• IP (Ingress Protection): protection against dust and water. An IP66, for example, protects against dust and powerful water jets · essential outdoors, in humid or dusty environments.
• IK: resistance to mechanical impacts, essential in industrial and sports environments or those exposed to impacts.

A luminaire over-equipped for sheltered use is an extra cost; an under-protected luminaire in an aggressive environment is a failure waiting to happen. The challenge is to choose the right level. For demanding environments, the Rexylum industrial range offers hardened products. References such as the REXSHOCK TUBULAR IP, anti-corrosion tubular luminaire, or the UFOBAY UB16, high-performance LED pendant, illustrate designs intended to last in difficult conditions.

Warranties and compliance: what a serious commitment must cover

The warranty is the contractual extension of the lifetime figures. A consistent warranty must specify its duration, its scope (luminaire, driver, even labour) and its conditions of application, in particular the admissible ambient temperature ranges and the number of operating hours covered. A long warranty is only of value if it is backed by credible reliability data (Lx/Bxx, driver quality): be wary of a generous duration displayed without technical justification. Compliance with European standards and markings (electrical safety, electromagnetic compatibility) is also a non-negotiable prerequisite for professional use.

Also think about the total cost of ownership rather than the purchase price alone. A reliable, efficient and well-guaranteed luminaire reduces maintenance interventions and replacements · a decisive advantage on installations at great heights or on large sites, where every operation mobilises significant resources.

How to judge an LED lighting supplier

Beyond the figures, several signs distinguish a serious supplier: complete data sheets stating Lx and Bxx, the make and characteristics of the driver, IP/IK ratings, colour temperature and CRI; clear and extended warranties, consistent with the stated lifetimes; compliance with European standards; and the ability to provide a photometric study. A supplier who only puts forward "50,000 hours" without specifying these elements deserves further questions.

FAQ

What is the difference between L70 and L80?

L70 indicates the duration during which the luminaire maintains at least 70 % of its initial flux, L80 at least 80 %. For the same duration, an L80 is more demanding and therefore more favourable: the light stays closer to its original value.

What does L80B10 at 50,000 hours mean?

It means that after 50,000 hours, 90 % of the luminaires maintain at least 80 % of their initial flux, and 10 % have fallen below it. The "B10" specifies the proportion of products concerned; the lower this figure, the more rigorous the promise.

Why is thermal management so important?

Because heat accelerates the decline in LED flux and the ageing of the electronics. The same component will last much longer if it is properly cooled. Thermal design is therefore the first factor in real lifetime.

Does the driver influence reliability?

Yes, strongly. The driver is often the first element to fail. Its quality, its sizing and its thermal resistance determine the overall reliability of the luminaire, especially on installations that are difficult to access.

Need a photometric study?

The audit and the photometric study are the work of a lighting design office: we recommend the expertise of the Luminance Consulting agency, the lighting design office that contributes to developing our ranges of luminaires based on an in-depth analysis of the needs of the most demanding customers. Luminance carries out the audit of your installation, the DIALux study and the compliance check. Rexylum, for its part, designs and supplies the prescribed luminaires and lighting solutions: for the choice of equipment, contact us.