When does an LED lamp need replacing?

Usually not when it goes out, but when it has become too weak. An LED rarely dies suddenly: it delivers steadily less light. The industry takes seventy percent of the original output as the point at which you call it worn out.

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What those 50,000 hours on the box mean

Not that the lamp is dead by then. The figure goes with an L value, and that says how much light still comes out.

• L70: after those hours the lamp still gives 70 percent of its original lumens
• L80: still 80 percent, so a stricter requirement and a shorter figure
• L90: still 90 percent, which only good fixtures reach

L70 is the common measure because a gradual decline to roughly that level goes unnoticed by almost everyone. Only below it do you start to see it, and even then usually only with a new lamp hanging next to it.

Sometimes a second letter is added, as in L70B50. That B is about how many units reach it. B50 means half the lamps still give 70 percent at that point, so the other half already give less. B10 is stricter: then ninety percent reach it.

How they arrive at that figure

This is where it gets interesting, because nobody runs a lamp for fifty years to measure it.

LED modules are tested to LM-80. That test runs for at least 6,000 hours, preferably 10,000, and measures the light output at least every 1,000 hours at various temperatures. The TM-21 calculation method then projects that forward.

And there is a limit to that. TM-21 allows you to extrapolate at most six times the test duration, with a sample of twenty units. With ten units it is five and a half times. A claim of 50,000 hours therefore requires at least around 8,300 hours of real testing, almost a year of measuring.

That is exactly why the rule exists. Without a ceiling, a manufacturer could turn a thousand hour test into a century of claimed lifespan.

What actually fails first in practice

The LED itself, rarely. The electronics in front of it, often.

If one spot goes out while the rest keep burning, look at the driver first. With a separate driver that is a block above the ceiling you can replace on its own. If several spots fail at once, there was a loop-through driver. That is set out further in Can you replace an integrated LED?

Heat is the biggest enemy of that electronics. A spot packed in insulation will not reach its stated hours, however good the LED itself is.

What we state

We list the lifespan per product, and the differences are large. In our catalogue it runs from 15,000 hours on the Plano and the Luma, through 25,000 on the Lesto, to 50,000 on the Lyvo and 54,000 on the Ferro.

That difference only counts where you cannot easily reach. If a spot burns three hours a day, 50,000 hours is over forty years and the figure is mostly theory. If it hangs in a shop open ten hours a day, it is thirteen years against four, and then it becomes a real choice.

Not every product carries a figure. Where the supplier gives no number, we do not fill one in.

So when do you replace it

Three signs are the clearest:

Visibly weaker than its neighbour. Hang a new spot beside an old one and look. If you see a difference, you are below seventy percent.

The colour has drifted. Some LEDs turn greenish or purple over the years. That is called colour shift and it is more annoying than light loss, because you do notice it.

It flickers. That is almost always the driver or the dimmer, not the LED. Check there before you throw anything away, via Why does your LED lamp flicker?

The range is at recessed spotlights.