LumiLife

What the datasheet actually promises.

Enter an outdoor luminaire's declared lifespan exactly as printed on the datasheet. LumiLife translates it, flags what is weak, and writes the questions to send the supplier.

The declaration

L value — lumen maintenance

B value — failure fraction

Declared life (hours)

Rated ambient ta °C

If the datasheet shows a range (e.g. −30…+50°C), that is usually the operating range — where the fixture functions, not where the lifespan holds. Enter the ta the lifespan is quoted at; use a higher value only if the manufacturer states the lifetime claim holds up to it.

Your project

Site ambient °C

Hours per night

Site ambient: realistic peak for the location, not the annual average. Hours per night: dusk-to-dawn is 11–12 h; used only to translate the declared hours into calendar years.

Continuous linear detail Cove, shadow-gap, facade line — anywhere the eye reads one unbroken line of light

The evidence — if you have it

What was tested?

Hours tested (LM-80)

Sample size (units)

Product / model — for the supplier email

What it actually promises

Flags

Questions for the supplier

What these terms mean

L value: Lumen maintenance — the percentage of original light output remaining at rated life. L90 means the light has faded to 90% of what it was on day one. L70 means down to 70%. L50 means half.
B value: The failure fraction — how many units are allowed to have faded below the L value. B10: at most 1 in 10. B50: up to half. If no B is printed, standards read it as B50. L70 B10 and L70 B50 share an L value and make wildly different promises.
C value: The fraction of units that may fail abruptly — no light at all — as opposed to fading gradually. Almost never printed on a datasheet, which is why LumiLife asks the supplier for it rather than asking you.
ta: The ambient temperature the whole declaration assumes, usually 25°C. Every number on the page is conditional on it. Not the same as the operating range: a fixture rated to function from −30 to +50°C does not promise its declared lifespan across that range — unless the manufacturer says so explicitly, in writing.
LM-80: The IES test method behind most lifespan claims. It measures lumen depreciation of the LED package alone — not the driver, housing, gaskets or optics — at controlled case temperatures, for a minimum of 6,000 hours.
TM-21 and the 6× rule: The IES method for projecting LM-80 data forward. A projection may not exceed 6× the hours actually tested (5.5× for samples of 10–19 units). IES PS-10-18 states that a 100,000-hour claim built on 10,000 hours of data "would not be supported by IES standards."
LM-84 / TM-28: The equivalent test and projection for the complete luminaire, driver included. Outdoors the LED is rarely the first thing to fail — LM-84 data is the stronger evidence.