UL Listed Outdoor String Lights
When a light source is operating, part of its energy is burned off as heat becoming infrared light. By looking at the graph above, incandescent light follows a very smooth curve that gradually goes up. Its strongest light is toward the red end of the visible spectrum. As light approaches the end of what we can perceive, most of its energy (up to 90%) is burned off making it invisible. Now let’s take a look at the LED bulb in the graph above.
Notice the difference in delivered light. Designed to target the visible spectrum, the highest spike of LED light is in the middle. Since LEDs also generate a lower amount of heat, they do not lose as much light on the infrared end. What this means is that LEDs appear to be brighter compared to incandescent bulbs because they generate a higher amount of light that can be seen by the human eye.
However, remember that true light output is measured in Lumens. This is why it is best to look at the Lumens when considering which bulbs to pick out. Sometimes LEDs can be listed with a certain wattage equivalent but vary on lumen output, exceeding the average lumen count of the light source it is designed to imitate. Going only by equivalent wattage can cause you to choose a light that is too bright for your intended purpose. To give you an idea of the standard output, the table below shows an average Lumen count per bulb wattage: