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LED bulbs are typically rated at 15,000 to 25,000 hours, which is 13 to 22 years at the 3 hours per day the FTC Lighting Facts label assumes. Real service life is usually shorter, commonly 5 to 15 years, because the rating describes the LED emitter and what actually fails is the driver electronics in the base. The rating also uses L70, meaning hours until output falls to 70 percent, not hours until the bulb goes dark. Heat is the dominant variable: the same bulb in an enclosed fixture can last half as long as in an open one.
What does the rated lifespan actually measure?
Two standards sit behind every number on a box. IES LM-80 is the test method for measuring lumen maintenance of LED packages, typically over 6,000 hours or more at controlled temperatures. IES TM-21 is the method for projecting that data forward, and it limits projections to six times the tested duration — so 10,000 hours of testing supports a claim of no more than 60,000 hours. A bulb advertised at 25,000 hours is describing the projected point at which the emitter reaches 70 percent of initial output under laboratory conditions.
What that figure does not describe is the electrolytic capacitors, driver IC and solder joints crammed into the base, which operate hot and are the actual failure mode in most bulbs that die early. It also does not describe your fixture, your ambient temperature or your power quality. Treat rated hours as a specification of the light-emitting part, not a prediction about the product.
| Rated life | At 3 hr/day (FTC label basis) | At 6 hr/day | At 12 hr/day |
|---|---|---|---|
| 10,000 hr | 9.1 years | 4.6 years | 2.3 years |
| 15,000 hr | 13.7 years | 6.8 years | 3.4 years |
| 25,000 hr | 22.8 years | 11.4 years | 5.7 years |
| 35,000 hr | 32.0 years | 16.0 years | 8.0 years |
| 50,000 hr | 45.7 years | 22.8 years | 11.4 years |
Anyone who has replaced an LED bulb after four years can see the gap between that table and reality. The table is not wrong; it simply describes a component under laboratory conditions rather than a product in your ceiling.
Why is heat the thing that matters?
Because every part of an LED bulb degrades faster hot. LED junction temperature drives lumen depreciation directly, and the electrolytic capacitors in the driver follow the familiar rule of thumb that their life roughly halves for every 10°C rise. A bulb that would reach 20,000 hours in a bare open fixture can fail in 3,000 in a sealed glass dome in a warm room.
| Situation | Effect on life | What to do |
|---|---|---|
| Open pendant or table lamp | Best case; full rated life plausible | Nothing |
| Enclosed glass fixture | Often halves it or worse | Use only enclosed-rated bulbs |
| Recessed can, insulation contact | Significant reduction | IC-rated fixtures; keep insulation clear where required |
| Base-up orientation | Heat rises into the driver | Choose bulbs rated for any orientation |
| Bulb in an unconditioned attic or garage | Cold is fine; heat is not | Check the stated ambient range |
| Bulb on an incompatible dimmer | Driver stress, flicker, buzz | Check the dimmer compatibility list |
| High or unstable line voltage | Driver failure | Surge protection; check for a shared-neutral problem |
Enclosed fixtures are the single most common reason people conclude that LEDs do not last, and the fix is a bulb specifically marked as suitable for them — covered in can you put an LED bulb in an enclosed fixture.
How do I judge a bulb before buying it?
Four signals, in order of usefulness.
- Warranty length. A manufacturer offering five years is exposing itself to real cost, which is a far stronger signal than a printed hour rating.
- ENERGY STAR certification. The lamp specification requires a minimum rated life and a minimum three-year warranty, plus limits on flicker, color shift over life and power factor. It is the closest thing to a floor on quality.
- The Lighting Facts label. Required by the FTC under its lighting labeling rule, it gives brightness in lumens, estimated yearly energy cost, life in years, appearance in Kelvin and energy used in watts — all in a standardized format you can compare across brands.
- Enclosed-fixture rating and ambient temperature range printed on the box, if that is where the bulb is going.
What is not a useful signal is the headline hour figure. Every brand quotes 15,000 or 25,000 hours and there is no practical way for a buyer to falsify it, which is why it has stopped carrying information.
How do LED bulbs fail?
Rarely by simply going dark. The usual patterns, roughly in order of frequency: flickering at low dim levels, then at all levels, as driver components degrade; total failure that comes on suddenly after a period of flicker; gradual dimming that goes unnoticed until a new bulb sits alongside; and color shift, usually toward green or pink, as one phosphor ages faster than another. In multi-emitter bulbs you sometimes see a partial failure where the output drops in a step as one string dies.
Flicker deserves attention beyond the annoyance. Persistent flicker on a dimmer usually means a compatibility problem rather than a dying bulb, and it stresses the driver so the bulb genuinely will fail sooner. It is closely related to the audible buzz covered in why LED lights buzz. Running costs across a bulb's life are worked out in how much it costs to run an LED bulb for a year.
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