Light-emitting diode, or LED, bulbs are much more energy efficient than "old school" incandescent bulbs. This means that it takes less power, or fewer watts, to generate the same amount of light, which is typically measured in lumens. As a courtesy, many manufacturers of LED bulbs package their products with the brightness equivalency to an incandescent bulb clearly shown.
More Efficient at Lower Brightness
While there is no simple conversion formula, LED bulbs tend to be more energy efficient than incandescent bulbs at lower levels of brightness than they are at higher levels of brightness. For example, to produce 450 lumens, an LED bulb needs 4 or 5 watts and an incandescent bulb requires 10 times as much energy -- 40 watts. Yet to produce 2,600 to 2,800 lumens, an LED bulb needs 25 to 28 watts and an incandescent bulb requires about six times more energy --150 watts.