LED Grow Light Distance for Growing Cannabis

LED Grow Lights

LED grow lights are powerful and can get great yields when used correctly. But when growing cannabis with LED grow lights it can be a little tricky to get the distance just right.
Unlike with MH/HPS/LEC grow lights, there is no "standard" distance to keep each LED grow light and it's hard to summarize with a quick chart like the others. The distance needed between an LED and the top of the plants varies quite a bit from model to model and from manufacturer to manufacturer. Many things can affect the optimal distance from plants, including the individual size of each LED bulb and the way the manufacturer used lenses to reflect light downwards at your plants.
Having the lights too close will cause the plants to burn and wilt, quickly killing them off. Raise your grow lights too high and the plants will stretch, causing the stems to be long and skinny leading to a very weak branch. Once the weight of bud growth reaches a couple of weeks, the branches will snap due to being so long and skinny.
Now before I show you the appropriate heights, I would like to mention two important items. First, these heights are applicable for both indoor and greenhouse grows. It does not change. Second, when hanging your lights you will want to consider the type of light you are using. For example, and LED light can get much closer to plants without burning them when compared to a HID  grow light. 
A simple test you can always use to tell if you are too close is hold your hand under the lights right where the tops of your plants are. If it is too hot for you to hold your hand there for 5 seconds, it is too close and the light needs to be raised.
Now lets discuss the appropriate height for your LED lights. The first thing to consider is what stage your plants are in. When in the Seedling stage, you want the light to be around 2.5-3 feet above the tops of your plants. Once you are in Vegetation, you can lower the LEDs to be around 2-2.5 feet above the tops of the plants. Finally, in flower you will want the plants to have a distance of 1-2 feet from the lights. As your plants develop and age, they will be able to handle more light at a higher intensity. You just need to slowly work them up to it is all. If you are not using LED grow lights, but a HID or some sort of Sodium bulb, I recommend adding foot to the heights I discussed above. Most importantly, always use the health of your plants as an indicator. Use the hand test as well and you will always be able to have your LED grow lights at the perfect height!

Light Distance for Growing Cannabis With LED Lighting

Unlike HID lighting, LEDs can produce far less heat, and will use less power overall. This can reduce energy bills massively, and a lot of growers are moving from the HID lighting to LED, as it is cheaper to run, and a more environmentally friendly option of grow lighting.
The problem here is that there are alot of makes and models of LEDs, and each one will have a specific height it will be optimal at. Most of the time, this height will be found in the owner's manual.
LED lights produce less heat, so it can be hard to tell if the plant is too close by using the back of the hand test. You can get LED lighting very close to the plants, but because the light is so strong, you can still damage your plants and cause "light bleaching".
Standard LED Lights
Each model of LED light will have different types of lenses and lights in them. These lights and lenses work together, to make sure the light is optimal at a certain distance, usually around 16 inches above the top of the plants.
It is not easy to tell the best light distance for growing cannabis with LED. But never bring the light closer than 14 inches, and if you see any signs of the plant turning white at the top, you need to raise the light immediately.
For a more specific answer you can ask for help in our cannabis growers forum. Many growers use LEDs, and maybe someone is using the same model as you are, so they can give you experienced advice on the best light distance for your LED light.
Quantum Boards
Quantum boards are a reasonably new type of grow lighting. They are efficient, and produce amazing plants. They are much like LEDs, and though they will not produce a lot of excess heat, they will still burn your plants if they get too close.
Because the light coming from QBs is so intense, they can easily light bleach your plants if they are too close. So always keep quantum boards grow light at a minimum of 16 inches away from the top of your plants.
If at any time, the buds or leaves, at the top of the plants start to lose colour, or become dry, raise the light immediately.
COB Lighting
COBs are another form of LED lighting, but they are made with far fewer diodes (lights). Instead of lots of lights, there will just be a few more powerful lights. Again, like most LED lighting, the distance you need to keep them from your plants will differ from model, and maker. You should check the instruction manual for the best light distance for growing cannabis.
Just because COB lights are small, you should not underestimate how powerful they are. They should be no closer than 12 inches from the top of the plants.