LED bulbs are much brighter than incandescent or halogen bulbs of the same wattage, but LED bulbs are not available in high wattages. Therefore, when replacing incandescent or halogen lamps with LED lamps, more LED lamps are often needed. The LEDs were designed to be more energy efficient, meaning they have a lower wattage for similar light output. Wattage used to be the main factor in brightness.
The higher the wattage, the more light the bulb emits. LEDs now have lower wattages to save energy, so it's no longer a good determination of light levels. A lumen is a measure of light. If the LEDs, CFL and incandescent lights all have the same lumens, they have the same brightness.
You can find the lumens in the bulb package. For the most efficient light, find the lumen output you want (the larger the brighter) and choose the bulb with the lowest wattage. LEDs are likely to win in all cases. The table below illustrates the amount of brightness in lumens you can expect from the different watts of the bulbs.
LED bulbs require much less power than CFL or incandescent bulbs, so LEDs are more energy efficient and last longer than their competitors. If an LED bulb is placed in a closed housing, the heat will have nowhere to go, sending it back to the bulb and sentencing it to a slow and painful death. Color changing technology allows you to adjust the color temperature of an LED bulb to suit a variety of purposes. Soft white and warm white will produce a candle-like yellow glow, close to incandescent, while bulbs labeled bright white or daylight will produce a whiter light, closer to daylight and similar to what is seen in offices and retail stores.
LEDs do not contain mercury and can therefore legally be thrown away, but it is best to recycle them. They are small semiconductors (diodes) wrapped in plastic to protect the elements and focus light. The first thing to do if you buy LEDs that you want to use with a dimmer switch is to make sure you buy bulbs that are, in fact, dimmable. Inefficient incandescent bulbs are being phased out, so you'll want to consider changing those expensive lights once and for all.
For example, a 4 W LED bulb has more than 220 lumens, while the same amount of lumens can be found in a standard 25 W bulb. This generates invisible ultraviolet light that excites a fluorescent layer (called a phosphor) inside the tube, which then emits visible light. From there, heat dissipates into the air and the LED bulb stays cool, helping to keep its promise of a long lifespan. It seems that they have always cost between 11 and 15 dollars for the guy who would screw into a standard lamp.