(pronounced LU-men dih-PREE-shee-AY-shun)
We’ve defined lumen for you, and you probably understand depreciation (especially if you’ve ever bought a new car and then tried to sell it after just one year). Put ‘em together and what have you got? Reduced lamp performance. (Not quite as fun as what Cinderella’s Fairy Godmother sang about, eh”) As lamps burn, their lumen output declines. In other words, a 75-watt incandescent lamp will give off more light when it’s first used than when it near the end of its lifespan. As we’ve mentioned elsewhere on P&C, the life of an LED lamp is much longer than that of an incandescent, fluorescent or HID lamp. An LED’s lamp’s lifespan is then measured by lumen depreciation because the LED never really burns out.