What is the difference between 1, 3, 5 and 10 watt diodes?
What are COB LEDs?
LED diodes are typically rated by the wattage (amount of power) they can handle if they are perfectly cooled. Since LEDs can't be cooled perfectly in real-world environments, they are usually run at lower actual wattages than they are rated for to extend their useful life and prevent them from "burning out".
LEDs are more efficient at producing light when less power is run through them-- but they also produce less light. While lower-powered diodes are more efficient, individually-packaged LEDs don't emit enough light to grow plants well.
LED grow lights using individual 1-watt (1W) diodes are bright enough to grow low-light plants like lettuce, but only when placed very close to the LEDs, but don't provide enough energy to get light-hungry plants to flower.
Grow lights with individual 3W diodes are a little brighter than T5 fluorescent bulbs and can be used to grow and flower short plants, but lack the light intensity needed to grow and flower taller plants without "concentrating" the light using secondary optics. These secondary lenses work like magnifying glasses, focusing the light away from the edges and corners of the lighting footprint into one bright spot directly under the light. While this light distribution pattern can yield PPFD statistics that, when properly manipulated, look good on paper- it doesn't work well in the real world for growing plants!
Individual 5W diodes are bright enough to provide canopy-penetration better than any HID light. We only use 5W diodes in our lights because they provide the best balance of efficiency and intensity available today when used without a protective glass lens.
10W LEDs are used in some LED grow lights but are "white" LEDs with an inefficient spectrum for growing plants but perfect for human eyes.
COB (chip-on-board) or "integrated" LEDs are circuit boards with many low wattage diodes. For example, a COB LED rated at 30 watts may have 30 1W diodes, or 60 0.5W diodes. COB LEDs are less expensive to produce because they minimize costs associated with packaging LEDs individually, and the lower-wattage diodes that comprise them are slightly more efficient. However, they cannot easily be made with primary lenses, so light-extraction efficiency suffers. COB LEDs are also "mechanically fragile": a simple touch of a finger is enough to break them, so they must be protected behind a glass lens or secondary optic, which steals 10% of the light. COB LEDs may be more efficient on a spec sheet than the 5W individual diodes we use, but when they are protected behind glass or plastic in a real-world situation, our 5W diodes without this light-blocking covering actually deliver more photons per watt to your plants. Most COB LEDs are also "white" LEDs with a spectrum perfect for human eyes but inefficient for growing plants.
Whichever type is used for the LED diode, lights must be evaluated based on the light output efficiency, intensity and spectrum for the entire fixture!