Quick guide on grow lights

Updated: Mar 13, 2020

Everyone agrees that knowing how to grow food indoors with grow lights is valuable. It improves your health, brightens your day, calms your nerves, and allows you to do more with your existence.


Grow lights are the most important environmental element affecting plant growth and development, because selection of grow lights can have a remarkable effect on the costs, operational costs, and quality of plants in your indoor grow room. This blog describes the physical properties of grow lights. Light sources often used in indoor grow rooms are introduced with a simple clarification of the fundamentals necessary to understand the grow lights. Particular importance is placed on LEDs, which have received extraordinary awareness recently, and on florescent lights, which are still commonly used in indoor grow room.

visible light chart

Physical Properties

Light is electromagnetic energy, which is also explained as electromagnetic radiation comprise both visible and invisible wavelengths. The smaller the wavelength, the greater the energy. The wavelength of visible light ranges from 380 to 780 nm, which is what people eyes see. Visible light is key to plants because it occurs simultaneously with photosynthetically active radiation (PAR, 400-700 nm). For solar radiation, 97% is inside the 280-2800 nm range. In this regard, 43% is visible light, which is practical for plant growth, 4% is ultraviolet, and 53% is infrared, which make heat. Only electric lights are used in indoor grow rooms. Light has two opposed properties: it can be notice as a wave phenomenon and it also acts as separate particles called photons. A photon is the smallest particle of light, or a single quantum of light. Light varies in at least three dimensions: quantity, quality, and duration. When electric lights are used in a indoor grow room, the lighting cycle, which affects plant growth and development, can be willingly changed. Light effects plants in two ways: providing energy or a quantum source and acting as an information medium. While an energy source, the photons of light, is caught by plants and a part (up to 10%) of photons caught by plants is converted to chemical energy (carbohydrates) through photosynthesis. Almost all of the light energy or photons caught by plants is converted into heat energy.

Light Sources

Till recently, most of the light sources used for indoor grow rooms were fluorescent lights and high intensity discharge (HID) lights. Till just a decade ago, LEDs were used almost exclusively for research on plant cultivation, but are now being used as a light source for commercial plant cultivation in indoor grow rooms because of their fast price decline and quick improvement in luminous efficacy, which is a measure of how efficiently an electrical lamp produces visible light.

led light


LEDs offer advantages over fluorescent and HPS lights: they are strong; produce a stable output; are long lived, compact, and lightweight; turn on right away; and allow the light output to be easily controlled with a light source consist of several color types of LEDs. Benefit of using LEDs as a light source for indoor grow rooms is that LEDs offer great flexibilty for making various light environments compared to conventional lights. A light source having a few types of LEDs with different peak wavelengths can produce light of which the spectral radiant inconstancy can be varied with time. The biggest disadvantage of using LEDs for indoor grow rooms is the high beginning cost for a set of LED lights, compared to conventional lights.

Fluorescent Lights

Fluorescent lights offer no direct advantage over other lights including LEDs. Tubular fluorescent lights are the most suitable light source at present for indoor grow room when taking into account all the factors of bulb and luminaire prices, rated life, luminous efficacy, ready availability, and lighted bulb temperature. A tubular fluorescent light normally consist of a glass tube coated inside with a fluorecent material (phosphor), two tungsten electrodes at the two inside ends that are coated with an electron emissive material, a tiny amount of mercury, and low vapor pressure insert gas (mainly argon) enclosed in the glass.

hid light

High Intensity Discharge (HID)

HIDs are a type of electrical gas discharge light, which generates light by means of an electric arc between tungsten electrodes sheltered inside a translucent or transparent fused quartz or fused alumina arc tube. HID lights make more visible light per unit of electric power adsorbed than fluorescent lights, since a larger proportion of their radiation is visible light in contrast to infrared. Yet, the lumen output of HID lighting can lower by up to 70% over 10,000 burning hours.

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