How Long Will LED Light Bulbs Realistically Last? LED vs CFL?

White LEDs have a limited life. They are made from a standard electronic LED (usually emitting blue light) which will last decades—maybe a hundred years—plus a phosphorescent organic dye which converts the LED light into a white spectrum. The dye wears over time and gradually produces less light. However, a LED produces approximately 20–40 times the light of a comparable wattage incandescent light, and around ten times that of a comparable wattage CFL.

Compact florescent lights have more complexity: they have electronics and a vacuum tube and florescent dye and generate an ultraviolet emitting arc through the tube. Air leaks and restart cycles cause wear on their innards.

Right now, prices for LEDs are dropping sharply while CFLs are relatively steady. I think the most prudent course is to phase in LEDs over the next few years as the purchase price of either type of light takes quite a while to amortize itself. Depending on the light's usage and power, it can take anywhere from 18 months to 20 years to recover the increased cost of a modern efficient light. To get the most bang for your buck, begin with the lights which are on the most: yard lights which are on all night, living room lights which are on every night for at least six hours. Save the hallway, basement, and bathroom lights for later since they tend to not get used more than a few hundred hours per year. Hopefully by then, LEDs will be almost free.

CFL's are quite cheap and save about 75% over incandescents, so its a no-brainer. I have CFL's in my house except in the bathrooms, because I want more natural light in the morning when looking in the mirror and bathroom lights rarely stay on more than a few minutes.

LED lights are still in their infancy but within 2-3 years they will be very common and much cheaper than they are now.

LED lamps last for a ridiculously long time - it's the drivers that tend to fail if not properly heatsinked, ventilated, etc.

They are more expensive, but I tend to recommend installing LED fixtures that have replaceable driver modules in addition to the LED lamp rather than retro-fitting LED lamps into existing fixtures - especially where the old fixture housings don't allow good ventilation.

When it's all designed to work together, it tends to work better.

They lose some of their brightness with time.

The "lifespan", however, is not the amount of time it will deliver light and then suddenly burn out; that generally doesn't happen - it's the point in time where the light output is so low that the user decides to replace the bulb.

If the voltage on them is a little less than they are rated at they will last 20 years or more.