Some of the most popular grow lights for indoor gardening are HID lights. The two best HID lights for growing plants are MH (Metal Halide) and HPS (High Pressure Sodium). For this article we will focus on the HPS or High Pressure Sodium lights.
High Pressure Sodium lights are usually used during the flowering stage of a plants grow cycle. This is because the HPS light bulb emits a spectrum that is red, yellow, and orange in color. This is going to be the light spectrum that mimics most closely the light that is produced by the sun later in the year, like fall time. This makes the HPS light ideal for plants that are in their fruiting and flower stage.
High Pressure Sodium HPS lights come in many different sizes. The most popular wattage's are 150w, 250w, 400w, 600w, and 1000w. You can find HPS lights in other sizes but the ones mentioned above are the most widely used. All HPS Lighting systems come with a ballast and cord set to run the light bulb. You will probably want to add a hood so that you can concentrate the light downward toward your plants.
When you are going to buy a HPS lighting system you will want to make sure that you get it from a reputable manufacturer. Sunlight Supply, HydroFarm, Sunleaves, and Lumatek are some of the good manufacturers. It is worth the extra money to get a HPS lighting system made by one of these guys, most also come with at least a 5 year warranty. I have personally used all of these brands, and although they have their advantages and disadvantages they are all solid products that the manufacturers back up with a warranty. You will never want to mix and match parts for a lighting system, it is very dangerous to do so and could cause a fire.
There are two types of ballast that will run a HPS lighting system, magnetic and digital. The magnetic ballasts are cheaper and more reliable, but they are bigger, nosier, and emit a good amount more heat. These have been the standard in the indoor horticulture industry for decades. The digital HID light ballast is relatively new to the market. People like them because they are smaller, quieter, and create less heat. That all sounds great, but keep in mind that they also have a much higher failure rate, and don't work well with some types of grow bulbs out on the market today. Mainly Hortilux bulbs have had problems with the digital ballast and more specifically the 1000w has had the most. I was told recently that Hortilux is finally going to adapt their bulbs to work with digital ballasts. When I stop running into people that are blowing up their Hortilux bulbs in digital ballasts I will let you guys know. For now be aware that this is a potential problem and talk with your local hydroponics/indoor gardening retailer to find out the latest information before spending over 0 on a bulb that will blow up on you. I would say that as long as you go with a brand from a reputable manufacturer that has a warranty either one is fine it's personal choice and budget that will play most on your decision.
Expect to change your HPS light Bulbs every 9 to 12 months. You may hear HPS bulbs can last up to two years, although this is correct in the sense that they will continue to emit light for two years, lumen degradation starts after only 6-9 months. So in order to get the maximum growing power from your bulbs you will need to change them out at least once a year.
Happy growing!
