More Light, Less Heat
Light-emitting diodes (LED) are semiconductors. As electrons pass through this type of semiconductor, it turns into light. Compared to incandescent and CFL bulbs, LED lights are more efficient at turning energy into light. Therefore, less of the energy radiates from the bulb as heat. This is why LED bulbs are cooler during operation than incandescent and CFL bulbs.
As the light-emitting diodes create light, they warm up quite a bit for their size. LEDs are heat sensitive, so it's important that the heat move away so that it doesn't damage the semiconductors. In order to do this, these lights need a system to keep cool. Most LED lights have a heat sink plate that moves the heat away from the light-emitting diodes through the heat sink plate. Manufacturers make the heat sink plate out of a variety of materials, but it's commonly made from aluminum. Frequently, the heat sink becomes part of the design of the bulb.
An LED light bulb's heat sink usually weighs several ounces and can become hot once you turn on the light. From the heat sink plate, the heat moves into the air surrounding the bulb. If you place the bulb in an enclosed fixture, it keeps the heat from effectively moving away from the heat sink, raising the temperature around the light-emitting diodes. This, in turn, causes the LEDs to overheat, shortening the life of the bulb.
Directional Light
Many LED bulbs have light-emitting diodes that all shine in one direction. This results in a bulb that directs most of its light toward the top of the bulb. If you place this type of bulb in a table lamp, you can see that most of the light ends up on the ceiling with very little refracted onto the table. In an attempt to make LED bulbs more like incandescent bulbs, omni-directional LED lighting is becoming more common. This lighting distributes the light evenly around the bulb. Commonly, it's done by bouncing the light off reflective plates inside the bulb.
An Aging Bulb
As LED light bulbs get older, they don't just burn out. Instead, they grow dimmer. The industry standard for LED light bulbs is that they should last for at least 25,000 hours with at least 70 percent as much brightness as they have when they are new. Below 70 percent is the point at which the industry decided the decrease in brightness is noticeable.
LED light bulbs are relatively new on the market, so they haven't been through the test of time – especially those that boast a lifespan of 50,000 hours. Although most of these lights last for about 25,000 hours, their warranties only cover about three years. This is perhaps because if you run the LED lamp continuously, it will only stay within the 70 percent range for a little less than three years. However, if you look on the Lighting Facts label of many LED lamps, it gives a life based on years. This is because the industry standard is three hours of use per day instead of 24 hours.