What Does High Intensity Discharge Lighting (HID) Mean?
High intensity discharge (HID) is a form of lighting used in indoor growing situations.
High intensity discharge grow lights produce an electric arc between tungsten electrodes housed inside a translucent tube. This electric charge excites gas molecules, which, as a result, produces a high-intensity light.
HID lamps are available in high pressure sodium (HPS), metal halide (MH) or ceramic metal halide (CMH) versions. HID lighting also includes double-ended lighting systems as opposed to single-ended traditional bulbs.
High pressure sodium (HPS) bulb.
Maximum Yield Explains High Intensity Discharge Lighting (HID)
Although many other types of lighting are suitable for growing, HID lighting is one of the first types that were used for indoor growing, and remain popular to this day.
High-intensity discharge lamps are considered a type of arc lamp. In earlier designs, mercury was the gas of choice. Today, radioactive gases such krypton-85 are more commonly used and produce the same effect.
HIDs make excellent grow lights because of the intensity of the UV rays and through the light produced. This intense light helps with the photosynthesis process for plants grown indoors.
HID lamps produce far more usable light that fluorescent or incandescent lamps since more of their radiation is visible light compared to infrared. However, the lumen output of HID lighting deteriorates over 10,000 burning hours, by as much as 70%. So, unlike fluorescent lighting and light-emitting diodes (LEDs), HIDs will lose their effectiveness over time. For this reason, the number of hours that the lamp is used as a grow light must be properly monitored in order to gauge replacement.
One reason for the rise in popularity of high intensity discharge lighting is the fact that it is available in different colors. This goes deeper than merely coloring the outside of the bulb. Different gases can create different wavelengths of light when heated, and these color differences will affect plants in a variety of ways.
For instance, high pressure sodium HIDs create reddish light, or light with a slightly orange tint. This is best used during the flowering phase of plant development. On the other hand, metal halide HIDs create more light in the blue spectrum. This cooler light is better suited for plants in the vegetative stage of development. With that being said, many manufacturers recommend using both metal halide (MH) and high pressure sodium (HPS) lights at the same time.
When choosing HID lighting, you’ll need to create your set-up to match your space. A single 1,000-watt bulb will cover about five feet by five feet. A 600-watt bulb will illuminate about four feet by four feet, while a 400-watt bulb will light up an area that’s a little larger than three feet by three feet. To improve effectiveness, HID grow lights should be used with reflectors. Light movers and timers are also beneficial in larger growrooms.