To state the unbelievably obvious, an LED grow light is simply a "grow light" that uses SP114D light emitting diodes (LEDs) in place of conventional forms of light production. So what's a grow light anyway, why would anyone want one and what does LED bring to the party?
There are many reasons to want to grow plants indoors (even though of course they naturally grow outside). The main one is to simply take control of their environment. Nature doesn't always provide what plants need - heat, light, water and nutrients - in the optimum amounts.By moving indoors then you can ensure your plants get exactly what they require at each stage of their development. The result is typically healthier specimens and better yields, which in turn often equates to a better return on investment for professional growers.
Now managing heat, water and even plant nutrition is not terribly difficult. But light? Well it's not as simple as you might imagine since plants are very particular about the exact type and level of light. Try growing anything in a room lit only by regular 100w household bulbs and see if anything is left alive after a week or so. It turns out that plants prefer light that falls into two broad parts of the spectrum - the blue and red zones. The green area that lies between these two is of little use to them, which is also why most plants are green in color. They convert light into energy via a process called photosynthesis that uses molecules of a substance called Chlorophyll. Chlorophyll absorbs red and blue light but reflects green, hence the green appearance.Which brings us back to the topic of grow lights. These must clearly emulate sunlight with a broad spectrum of light that encompasses the two (actually four, two types of blue and two types of red, but let's keep it simple) important zones that drive photosynthesis.
The problem historically has been that most lighting technologies are really bad at producing light at all (they mostly produce heat) let alone the "right sort" for plants. To compound the problem, most plants favor blue light when young and shift more towards red as they mature. Step forward the LED. These can be made to emit light at just about any spectral frequency required and unlike regular lighting they do in fact create mostly light with very little wasted heat. And being electronic devices they are also highly controllable. If you've ever seen the range of colors that LED stage lighting is capable of (if you've been to any kind of show recently then it's a near certainty that you have) then you'll get the idea. Changing phases from two specific frequencies of blue to two of red might be immensely challenging for regular lighting systems, but for LED based ones it's a stroll in the park.
The reason that LED grow lights are apparently the latest thing is that until recently they weren't either bright enough or manufactured in sufficient quantities. But that's all changed and continues to change very rapidly indeed.There's also another interesting set of side benefits associated with LED grow lighting. Because they give off virtually no heat, not only is it easier and cheaper to maintain the correct temperature, but the lights can be placed much closer to the plants. Why is this a good thing? The Inverse Square Rule of light - as the distance between plant and light is halved the amount of available light is squared (i.e. move a light source from 4 feet to 2 and the light level will increase from say 400 lumens to 1600).
And of course, with low heat loss much less electricity is needed to power LED grow lights, which for larger installations can provide very significant savings in operating costs. They also don't need constant replacement since they last many, many times longer and are generally far more robust and a great deal lighter (in weight that is). And let's not forget some of the somewhat less than eco-friendly aspects of some other types of lighting (mercury in fluorescent tubes for one example).
So back to the original question: do LED grow lights deserve the hype? Well, yes actually, they do.