What is the Optimal Height for LED Grow Light Above Plants

Indoor growing is a great idea to grow plants with less space but a higher yield. LED grow lights are widely used for indoor growing due to their ability to mimic natural light. Most LED grow lights are full spectrum while others are typically designed for certain growing stages. Supplemental lighting allows plants to grow robust and better. However many growers doubt the optimal height for LED grow lights above the plant canopy. Either too close or too high distances from LED grow lights to plants are negative to the growth. This problem is complex as answers vary from growing space, plant cultivar, growing stage of plants, wattage of LED grow light, etc. This post would talk about the optimal height for LED grow light above plants.

Effects of different heights above plants

To figure out the optimal height of LED grow lights above plants, we need to know the effects of different heights on lighting and plants. In simple terms, the height of LED grow light above plants does not affect the total amount of light but the lighting uniformity and lighting intensity. LED grow lights emit the light and then the light shines on the plants. The amount of light emitted by grow lights is not influenced by the distance between LED grow lights and plants. Image that a bottle of water is poured from the canopy or the ceiling of the growing room. Neither higher nor lower location of the water will change the amount of water. It is the same as LED grow lights.

However, lighting uniformity and intensity are affected by the height from the LED grow light to the plant canopy. LED grow lights emit light in certain throws and fields. Uniform light distribution means plants and the growing room are illuminated evenly. Uniform light distribution conduces to more even plant growth, easier management, and higher yields. Improper distance makes light fall into aisles instead of plants. The lost light not only wastes energy but also money since growers have to pay for the extra electricity bill.

Light intensity is generally measured by PPFD. PPFD (Photosynthetic Photon Flux Density) refers to the total amount of photons that fall into a unit square meter per second. The higher LED grow lights are placed above plants, the lower light intensity plants receive (in the same area). Excessive lighting including over light intensity and duration will cause plant burns and drying. Insufficient light intensity, however, will cause plant wilting and decrease the yields.

Factors of optimal height from LED grow light to plants

The optimal height for an LED grow light above plants is related to growing space, plant cultivar, growing stage of plants, the wattage of the LED grow light, etc. A distance of about 12 to 38 inches (30 cm to 96 cm) from LED grow lights to plants is suitable for most conditions. However, the concrete lighting strategy should be made according to specific circumstances. Growers must observe the plants carefully and adjust the height from LED grow lights to plants in time. Some LED grow lights are equipped with a dimming function, which means the light intensity can be adjusted simply by switching the button. Here are some recommendations based on the wattage of LED grow lights and the growing stage of plants.

Wattage

Generally, LED grow lights with higher power are designed with higher PPF output and larger dimensions. In other words, LED grow lights with higher wattage have higher light intensity when lighting areas of the same size. Thus, LED grow lights that have high wattage should be placed further away from plants, while low-wattage LED grow lights can be posited closer to plants. Powers of common LED grow lights range from 20W to 1000W.

• If the LED grow light is lower than 200W, the height for the LED grow light above plants should not exceed 12 inches.
• For the wattage between 200W to 400W, keep the LED grow light about 12 inches to 20 inches from plants.
• The height of about 20 inches to 28 inches is suitable for LED grow lights in 400W to 600W.
• For up to 800W, LED grow light can be placed up to 38 inches above the plants.
• If the LED grow light is larger than 800W, you can go up to 42 inches.

Here is a table about the recommendations of the heights (from LED grow light to plant canopy) for LED grow lights in different wattages.

Growing stage

Since plants grow taller and more robust from seedlings to the flowering stage and the plants have different lighting needs at each stage, the height between the LED grow light and plant canopy should be adjusted according to the development of plants. There is little light requirement for the seedling stage. Therefore, LED grow lights could be hung far away from plants to save energy and avoid leaves burning.

• Lower wattage LED grow light and further distance to plants are ideal for the seedling stage. A height of about 30 inches above plants is applicable for the seedling stage.
• When plants move to the vegetative stage, they need more light and energy to support their growth. The height of the LED grow light above plants could be shortened to about 24 inches.
• For the flowering stage, plants usually reach the maximum height. LED grow lights could be placed closer to plants during this stage. But it may cause leaves and flower burn if the LED grow light is too close to the plant. The distance between LED grow lights and plants could be 15 inches to 18 inches.

Here is a table about the recommendations of the heights (from LED grow light to plant canopy) for LED grow lights in different growing stages.

If you want to grow healthy and productive plants, you need to provide them with the optimal amount of light. But how do you know how far to place your LED grow lights from your plants?

There is no one-size-fits-all answer to this question. The optimal distance depends on several factors, such as the type and size of your plants, the wattage and spectrum of your LED lights, and the size and shape of your growing area.

That’s why we offer a personalized service to help you find the best light plan for your indoor farms and greenhouses. We will not only tell you the recommended height for your LED lights but also design a free light plan that maximizes the lighting performance and efficiency for your specific needs.

Contact us today and let us help you grow better with LED lights!