About 1, 3, 5 and 10-watt diodes and COB or "Integrated" LEDs
LED diodes are rated by the amount of power (wattage) they can handle if they are perfectly cooled. Since LEDs can't be cooled perfectly in real-world environments, they are run at lower actual wattages than they are rated for to extend their useful life and maintain spectral quality.
As less power is run through an LED, it becomes more efficient at producing light-- but it also produces less light. While lower-powered diodes are more efficient, they don't emit enough light to grow plants well.
1-watt (1W) diodes are bright enough to grow low-light plants, but only when placed very close to the LEDs, and they don't provide enough energy to get most plants to flower. 3W diodes are a little brighter than T5 fluorescent bulbs and can be used to grow most plants within a couple feet of the LEDs.
5W diodes are brighter still and provide canopy-penetration equivalent to or better than a 1000W HID light. Black Dog LED only uses 5W diodes in our Universal Series lights because they provide the best balance of efficiency and intensity available today.
10W LEDs are now available but are mostly "white" LEDs, which are inefficient for growing plants but wonderful for lighting your home or office. Blue 10W LEDs are also available (these are the base for the "white" LEDs) but the other colors necessary to create our Phyto-Genesis Spectrum™ just don't exist yet as 10W LEDs.
COB (chip-on-board) or Integrated LED lighting is simply printed circuit boards with many low-wattage diodes directly mounted. For example, a "50W" COB LED may be comprised of 50 1W diodes, or 100 0.5W diodes. By minimizing the costs normally associated with packaging LEDs individually, the COB LEDs are cheaper to produce, but they cannot easily be made with primary lenses, so efficiency suffers. Another limitation with large COB LEDs is that heat cannot be removed fast enough to allow them to use high-power diodes. Some COB LEDs are now available constructed of 3W diodes, but they can only be run at a third of their rated power and tend to burn out after just a few weeks due to excess heat.