LED Grow Lights are now competitive with and at times outperform older HID technology. The best LED grow lights that give the highest yield per watt will have the most favorable spectrum for plant photosynthesis. LED lights that have 7-8 wavelengths of light along with UV and infrared will give the highest yields and the healthiest, highest quality plant production. It takes 7-8 wavelengths to replicate the photosynthetic action radiation provided by the sun for plant photosynthesis and this is the ideal blend for the highest yielding LED grow lights.
Lights that have less than 7 wavelengths will be missing some critical spectra and will not provide the same high quality of growth as lights with the ideal spectra. Conversely, led lights with more than 8 bands are providing excess wavelengths, which do little or nothing to enhance plant quality and yield and can actually reduce plant growth and resin production. If more wavelengths were better when it comes to plant production, we would want the LED grow light to encompass all the wavelengths of light. This is not the case, so the excess wavelengths make the lights less efficient. The result is a lower yield per watt when there are too many wavelengths.
The highest yielding LED Grow Lights have the red and blues, which are the most basic wavelengths necessary for indoor plant growth. In addition to these basic colors, there should be a weighted average of yellow, orange, violet, and ultraviolet wavelengths corresponding to the secondary and tertiary photosynthesis peaks. Add infrared and round off the spectra with a bit of white and you have the ideal configuration for a top yielding grow light.
The reason LED grow lights are so efficient is their ability to target specific wavelengths and bar excess wavelengths. HID lights on the other hand give off white light, which encompasses all the color of the light spectrum. This is why metal halide and high pressure sodium lights are so bright, give off so much heat and are not nearly as efficient as LED grow lights. The goal with LED grow lights is to maximize plant growth and yield, not to maximize brightness.
To illustrate this point, consider the red colors, which along with the blues make up the basic colors needed for plant production. Red wavelengths are not bright at all, but are essential in a grow light. Another interesting point is about green wavelengths. Green wavelengths are reflected by the plant cell structure and waste energy without adding to plant production or yield. To get the highest yields possible with LED grow lights, it is important to have the 7 to 8 bands of light in the correct amounts.