The Myths of LED Grow Lights

By Christopher Sloper, author of “The LED Grow Book.”

Unfortunately there are many many myths that surround LED grow lights.  What do you say we set the record straight for three of the most common ones?

No heat.  Yeah right!  This is my favorite LED myth.  Heat is an insanely complex topic, but there are a few simple rules we mere mortals can understand.  By scientific definition, 1 watt of electricity produces 3.41 British Thermal Units (Btu) of heat.  This means for every 1000 watts consumed regardless of light type (HPS, LED, fluorescent, etc.), 3,410 Btu of heat is produced.  Period.

Where did this myth come from?  LEDs generally use about half the watts used in HPS/MH lamps.  This means replacing a 1000 watt lamp will require about 500 watts of LEDs.  Early LED grow lights were underpowered and so produced little heat.  Also, HPS/MH lamps immediately convert about half the energy they consume instantly into infrared light:  the same stuff that keeps food warm at restaurants.

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LEDs can’t burn plants. With modern LED grow lights, plants can be damaged if the light is too close, but it’s a different type of stress than the downward heat pressure caused by HPS/MH lamps.  LEDs can provide plants with too much light to process, to the point they begin to defend themselves instead of growing and reproducing.  This process is called photoinhibition, which can cause photobleaching —the tops of the plants turn completely white.

Where did this myth come from?  It’s also left over from the early days when LED grow lights which used much less powerful LED chipsets that didn’t have the punch of today’s evolved versions.  Those lights could be hung like fluorescent lights – very close to the plant canopy — without bleaching.

The last grow light you will ever buy. This myth is based on the longevity of the LED emitters themselves.  The typical useful life of today’s LED is about 50,000 hours, which means it will have a lifespan of over 11 years when used for a 12 on/12 off light schedule.  Although it’s a great sales pitch, most of us gardeners like new toys now and again.  LED grow lights are constantly improving, so it’s likely a user will want to upgrade before a light’s useful life is up.

About the author:  Christopher Sloper is the author of “The LED Grow Book” which is available for sale from any of Hydrofarm’s dealers.  Be sure to check out the book for more invaluable LED lighting information.image-1.php