There are several types of lights, but below are the four most common ones you'll find in a grow space. There are numerous variations within each of these four kinds as well, and new lights and technology emerge all the time. Lights have components and bulbs, and some require a ballast. Depending on the type and model, the bulbs or the components can be more expensive. There are a lot of acronyms, but don't be alarmed.
HID lights
HID (high-intensity discharge) is an umbrella term under which MH and HPS bulbs fall, which we'll discuss more below. These types of lamps have a hood that reflects light and bulbs that are enclosed capsules containing a gas, as opposed to bulbs you 'd find in your house, which have a filament that heats up.
For HIDs, light occurs as an arc between two nodes inside the bulb. The gas contained in these bulbs is what makes MHs and HPSs different. HID bulbs are usually more costly than the reflective hoods that hold them.
HIDs have been the standard in indoor weed cultivating for years, however LEDs are quickly catching up to them.
Both types of HIDs are usually inexpensive to purchase yet will eat up electricity. HIDs throw off a lot of light and heat, which the plants need to grow and get potent. But, they run hot, contain heavy metals, and ballasts can fail.
Nevertheless, because of their low cost, if you're new to indoor cultivating and unsure how frequently you'll do it, you might want to buy an inexpensive HID light at first to test the water.
MH (Metal halide)
These bulbs contain mercury and metal halides, produce a bluish light, and are commonly used for vegetative growth. They need a ballast to regulate the current. In the past, ballasts have been big and bulky, but digital ones are now available.
HPS (High-pressure sodium)
These HID bulbs usually contain sodium, mercury, and xenon, and generate a yellow/orange light, as well as are generally utilized for flowering plants. Some cultivators will start plants under MH bulbs and switch them to HPSs when plants go into the flowering stage, using the same hood. These lights also require a ballast.
CFL lights
CFLs (compact fluorescent lamps) are fluorescent lights similar to what you would find in a school or office building, but smaller. For growing marijuana, they are typically called "T5s"-- the "T" stands for "tubular" and the "5" represents its diameter, "⅝".
There are daylight bulbs and warm white bulbs; the former better for vegetative growth, and the latter for flowering.
These fluorescent lights are cheap and efficient and great for vegetative growth. They're especially good for helping along germinating seeds and small seedlings because they do not emit much heat and will not burn the fragile seeds. They will not run up your electricity bill too much.
The disadvantage to CFLs is they aren't great for flowering plants, and growers will commonly utilize a different kind of light to finish plants. CFLs just don't generate enough strong light for plants to pile on weight.
Fixtures come in all shapes and sizes and can usually fit 4-12 long fluorescent bulbs; a standard size is 8 bulbs. Fixtures usually have a reflective material to bounce light in one direction, down on your plants.
LED lights
LEDs (light emitting diodes) are fairly new to the cannabis cultivating scene, compared to HPSs, MHs, and CFLs, but they are quickly proving to be the way of the future. LEDs might be more pricey to purchase at first, yet they are much more effective and kinder to the environment and your electricity bill. Some cities even give tax breaks to commercial cultivators who install or change to LEDs because they're better for the environment.
LEDs also typically run a lot cooler than HIDs, so you may not need additional equipment to cool your grow area, and one LED can typically be used for both vegetative and flowering growth. Some high-end LEDs enable you to adjust the spectrum for each growth stage.
New LED grow lights emerge all the time, however knockoffs are all around. There are a lot of cheap LEDs that do not generate the best spectrum of light for plants.
