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How Far Should LED Grow Lights Be From Plants


How far should LED grow lights be from plants? Most LED grow lights come with specific guidelines but will vary from setup to setup and also from plant to plant.

The rule of thumb: always start with the guidelines provided by the manufacturer, often 18-24 inches away from your plant. Also, keep a keen eye on the plants for any sign of too far away or too close lighting.

Why Hung LED Grow Lights at Different Heights?

You need to note that not all LED grow lights are alike. Every light needs to be hung uniquely to avoid under or overexposure of the plants to the light.

Although these lights might provide the same light the plants require, their spectrum and intensity are different and you shouldn’t hung them in the same way.

High-Intensity Discharge Grow Light Spacing

HID grow lights produce a powerful amount of heat when you turn them on. Hence, you shouldn’t place them near your plants as they can easily dry your crops.

Below is a guide of how far you should install HID grow lights, depending on the wattage:

  • 400-600 watts: 12-19 inches from the plants.
  • 600-1000 watts: 14-26 inches from the plants.
  • Over 1000 watts: 16-31 inches from the plants.

This doesn’t mean that you place your HID grow lights extremely far away from the plants even if they produce high intense heat. Underexposure to these lights will result in problems.

Fluorescent Grow Light Spacing

Fluorescent grow lights come in different types including T5s, T12s, and CFLs. Hence, there will be a huge difference when it comes to installing them over your plants.

T12s and T5s don’t produce sufficient light that can burn or stress your plants but note that T5s have higher light output. Also, note that T12s are less intense than T5s.

On the flip side, CFLs produce heat that builds up, especially the compact models. However, they are not quite intense to produce heat that can burn or stress your plants.

The rule of the thumb when using fluorescent grow lights is to simply keep them 12 inches from your plants. You can adjust them later when your plants grow.

High-Pressure Sodium and Metal Halides Grow Lights Spacing

Metal Halides and HPS grow lights come in kits that help to offer the required spectrum to the plants.  HPS is recommended for the flowering phase while metal halides provide the cool spectrum that is ideal for the vegetative phase.

Here is a simple guide that you should use when installing the two lights:

  • 150 watts: 8-12 inches from the plants.
  • 250 watts: 10-14 inches from the plants.
  • 400 watts: 12-19 inches from the plants.
  • 600 watts: 14-25 inches from the plants.
  • 1000 watts: 16-31 inches from the plants.

As always, you need to adjust the distance as your plants continue to grow. In case you forget, the lights will easily burn or hurt your plants as they get taller.

LED Grow Light Spacing Guide

You won’t come across a formula that will help you compute the distance for installing your LED grow lights.  With that said, these should be the standard to guide you when placing your lights:

  • 1 watt: 16 inches from the plants.
  • 3 to 5 watts: 20 inches from the plants.
  • 6 to 10 watts: 21 inches from the plants.
  • 200 watts: 12-24 inches from the plants.
  • 250-400 watts: 16-30 inches from the plants.
  • 450-550 watts: 20-35 inches from the plants.
  • 600-800 watts: 28-42 inches from the plants.
  • 900-1000 watts: 36-46 inches from the plants.

Light Levels Measurement (Lux Meter)

You can use a lux meter to measure the brightness level of your LED grow lights. This will help you to have a better idea of how far you should place your lights from the plants.

Note that lux meter won’t measure the heat produced by the lights, but only the brightness. Specifically, lux meter will measure the brightness as your eyes would see it.

Although you won’t know the heat, brightness can help you to determine how your plants will do at various levels.

Lux meter measure should follow these guides:

  • Vegetative stage: 15,000 to 70,000 lux
  • Flowering stage: 35,000 lux
  • Seedlings and clones: 5,000 to 7,000 lux

Remember that grow lights can easily burn or wilt your crops even if they do not produce extreme heat. Hence, if you want to be safe, place your lights as far as you want.

The important thing is to ensure that all the plants are equally lighted. In fact, grow light spacing is always a trial and error process, so be patient and keen to see how your plants respond from various distances.

In Conclusion

There is no right or wrong distance for installing LED grow lights. However, you should ensure that your plants respond positively to the distance you choose.  Avoid over or underexposure of the lights.

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