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What are LED Grow Lights?

Daphne Mallory
Daphne Mallory

Light emitting diode (LED) grow lights are a form of technology often used to provide plants and flowers with sufficient light to grow in greenhouses and indoors. It is an alternative to high intensity discharge (HID) lighting and metal halide (MH) lighting, which often use up to 75 percent more power and produce more heat than LED grow lights. Whether for commercial or non-commercial use, LED grow lights usually offer energy savings and are easy to install. They can also be combined with solar and wind technologies to maximize savings on electricity bills.

Manufacturers of LED grow lights often measure the brightness in lumens or lux. These measurements refer to how bright the room appears when the LED light is turned on. This is not indicative of how well plants will grow, however, because it is not based on photosynthetically active radiation (PAR), which is the part of the spectrum plants use. The micro Einstein measurement is often a better way to measure the ability of a lamp to grow plants. The human eye cannot see more 60 percent of the light that LED grow lights emit, and therefore lumens and lux measurements can often be misleading as to the amount of light the plants will absorb.

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LED grow lights are often comprised of a single light bar with several LED bulbs installed. Each light bar is mounted directly above the plants or flowers, usually no closer than 12 inches (30.48 cm). Depending on how many plants there are, it often takes several light bars to help the plants grow. It is important not to look directly at LED lights for long periods, because it may harm the eyes.

The main benefit to using LED grow lights is the ability to deliver high intensity light in indoor spaces. This light can extend the growing season by allowing plants to be grown indoors prior to transplanting outside, or even as an alternative to gardening outdoors. Grow lights are also great for plants that don't require heat to grow, because the heat output is low.

For many users, LED lights are preferred over HID lights for several reasons. The ballasts of HID lights are often noisy, while most LED lights are nearly noiseless. The lifespan of LED grow lights is typically about 50,000 hours; the lifespan of HID lights varies by type, but is typically less than half that of LEDs. LED grow lights are directional, while HID lights need reflectors to direct the light.

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Discussion Comments


@georgesplane- I watched a few LED grow light video reviews and the LED lights outperformed the HPS lights every time. The reviews used light set-ups of equivalent wattage with very similar square footage and plants. The yield on the LED set-up was about 40% better than the yield of the HPS set-up under similar conditions.

I do not know what the price difference is, or which product lasts longer, but as far as energy use is concerned, the LEDs are better. You should weigh the energy savings against the costs of purchasing and maintaining the two types of systems before making your purchase. This will give you the full operating costs of the two technologies.


@Georgesplane- From a purely scientific standpoint, LED grow lights should offer the same benefits of high-pressure sodium or metal halide lights for about half of the energy costs. LED growing lights waste less energy in heat, so they are much more efficient.

What matters as far as the plants go however is the amount of light in specific spectrum that a plant can absorb. As long as the light set you are looking to buy has the appropriate light spectrum for those types of plants, your yields should be just as good (possibly a little better) than conventional full spectrum light sets. It could possibly be better because LEDs are much cooler, making it possible to position the light loser to the plant, thus allowing more light absorbing.

As the technology becomes more developed, you will probably find light sets developed for specific species or types of plants. The light spectrum emitted by LED arrays can be adjusted to give precise percentages of light wavelength. This will allow for special lights for flowering plants, tubers, leafy plants, etc.


How do LED grow lights compare to conventional grow lights as far as the amount of light absorbed by the plant? Will a plant grow better under a 1000-watt HID or HPS light or a comparable sized LED light set? I am thinking about purchasing LED plant grow lights, but I do not know much about them. There are many rumors swirling about LEDs, but I would like something efficient, something that grows plants well, and something that uses less energy.

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