While shopping for LED bulbs, you may have been puzzled by the wide variation in rated life. I suspect you saw bulbs rated for 25,000 hours, others for 30,000 hours and even 50,000 hours. A couple of years ago the number 100,000 hours was even used as a way of making the case that the LED is a “forever” bulb. That hype has thankfully disappeared. Nevertheless, wide variations of LED rated life remain today. Here’s a brief explanation.
Let’s start with what is familiar. For incandescent and halogen bulbs the life of the bulb is rated by manufacturers base on when the bulb typically “burns out”. For most incandescent bulbs that is roughly 1000 hours, for halogen about 2000 hours. The fact that light output declines slightly over the life of these bulbs does not matter because the human eye does not notice. When the light level drops at least 30%, that’s when we notice. For halogen and incandescent, the filament breaks long before the 30% decline in light is reached.
There are no filaments to break with LED, a solid state technology. What happens instead is that at around 25,000 hours for most LED bulbs, the light output falls below the magic 30% level. In other words, LEDs don’t go dark or “burn out” before they need to be replaced. They get to a point where they don’t produce enough light and that is probably around 25,000 hours. If you see rated life listed as 30,000 hours or higher for an LED bulb, make sure the bulb is Energy Star qualified. That means the bulb has been tested to show that the 30% decline in light does not occur until 30,000 hours or whatever the rated life.
Bottom line, unless an LED bulb is qualified by Energy Star to last longer, assume it will produce useful light for 25,000 hours. In case you are wondering, that is a long time. Assuming the bulb is ON five hours every day, your LED bulb should last about 14 years.
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