It was way back in the late 70s when HID lighting for indoor growing first began to catch on. Prior to that the price of cannabis was so low that indoor growing really was quite the rarity. People just didn't do it and the hobbyists who did really didn't take it near as seriously as folks do now.
But the late 70s and early 80s also saw the introduction of what was referred to back then as 'sensimilla”, a new tastier, fragrant, green, unpressed variety of smoke that sold for about $20 an eight ounce. Quite a bit of money back then, considering that Mexican schwag was still going for about $15 an ounce.
So people began to take indoor growing a lot more seriously. They also started in looking around for better sources of lighting than fluorescent grow bulbs. The type of light that people used at that time and what they landed on was the 1000 watt metal halide bulb.
Back then when they were first picked up by growers a 1000 watt bulb sold for about $80 and the ballast went for about $150. So you can double that to account for inflation which would make the bulb around $160 and the ballast about $300 if they were repurchase with today's dollars.
So prices have for sure dropped considerably since then because you can now find 1000 watt bulbs for sale on the Internet brand-new for as little as $20 and do-it-yourself ballast kits for about double that. So this brings me to the first thing to be pointed out about HID lighting.
That is that it's cheap, particularly if you're thinking in terms of one 1000 watt bulb in a small bedroom that's been converted into a grow room. Even so, when compared to some of the newer lighting technologies like LED in particular HID lighting does have its fair share of shortcomings.
The first of them is that they burn hot, so they generate a lot of heat in the room. Then if you have the ballast in there along with the light you can easily into a heat problem. Heat leads to high humidity, and the heat and humidity make for perfect conditions for insect infestations, mold, root fungus, and slow growth.
Now if you're just starting out and are undecided whether or not you're going to go with a metal halide system don't take this heat issue lightly, particularly if you live in a climate where you have warm summers.
Now if you can place your ballast somewhere out of your grow room though, like perhaps up in an attic that takes care of a good chunk of the heat problem.
Now you can always go with a high-volume turbo-fan to vent the heat out of your room with, but keep in mind that if you're in the middle of the summer in a warm climate the air that you're blowing into the room may not be cool enough to do the job.
Next an HID bulb uses more electricity than a comparable LED light set up will, about 75% more. Now this really isn't a big problem if you're planning on running one or maybe two bulbs in your room. However, if you're planning on going beyond that, high electrical bills might become a problem for you in terms of concealing your operation.
Then a lot has written about the difference in the amount of red and blue spectral light produced by both metal halides and LEDs, and LEDs do come out on top here. Even so, it's not as though metal halide bulbs are weaklings in this area either because they're not.
A 1000 watt HID bulb will adequately cover a 10' x 10' area if it's properly distributed with a rotating light fixture. Then if you get a chance to look at some side-by-side comparison pictures of plants that were grown under both metal halide and LED lamps you'll see that there's really not a huge difference in terms of volume and vitality.
So in the end what it all boils down to is cost and the heat issue. For someone who was looking to set up a decent sized grow room, and who doesn't have thousands of dollars to spend on an advanced LED light system HID really is their only option. It's not a bad option either if you can deal with the heat that they will generate.
Now the cost of LED lighting is projected to come down in the coming years, and it has been already to some degree. Even so, it's going to be at least a decade until prices on LED lighting will come down to the point where it will start to nose metal halides out of the market.The Bottom Line
Metal halide bulbs along with their ballast generate a high amount of heat, heat that can be a problem in warmer climates. However, in colder northern climates the heat that they generate can actually be a 'plus'.
Metal halide lights are also by far the more affordable choice, and it will be years until LEDs can challenge them in terms of upfront cost.
HID bulbs are proven producers, so in spite of all the technical information that's presented in comparisons between HIDs and LEDs the standard 1000 watt workhorse is more than adequate for indoor growing.
HIDs use 75% more power 'watt for watt' when prepare to LEDs. Even so, as long as you aren't considering a large multi-bulb operation the energy consumed by one or two 1000 watt bulbs is not that big an issue.