The most important choice is the wattage. The wattage of the light will determine how much area you can light up. If we assume that the plants will get no sunlight, a 1000 watt light will cover about 7x7 feet of growing area. A 600 watt will cover 6x6 feet, a 400 will cover 4x4 feet, a 250 will cover 3x3 feet and a 150 will cover 2x2 feet. Higher wattage lights will cost more to operate, you can estimate operating cost with our cost calculator.
The next choice is the type of light. We have Sodium, Halide and Fluorescent. Sodiums are the most efficient and a best for flowering plants. The Sodium light is yellowish in color like the autumn sun. Halides are best for leafy crops with lost of foliage, it's a white light and more natural in color. Fluorescent lights are lower in light output than the others but are better for starting seedlings or cuttings. You can start seedlings with Sodiums and Halides if you keep the light farther away from the plants.
Seedlings and Small Plants
Small low wattage lights are best for seedlings.
For large plants you need the bright light that halides and sodiums can give. These lights range in power from 100 to 1000 watts. The 400 and 1000 watt lights are the most useful. A 1000 watt grow light can light up an area of about 7 feet square when the light is suspended 2 feet above the plants. A 400 watt light would work for an area of about 4 feet square.
Metal Halide also called Halide or just MH, emits a white light and is used for plants with lots of foliage. Halides are usually used for the beginning stages for plant growth, before flowering. The halides are not as bright and efficient as sodiums but they do have a better overall color spectrum for plants. The bulbs dont last as long as sodiums. They are less expensive than sodiums because there are fewer parts in the ballast and the transformers are smaller.
High Pressure Sodium
High Presure Sodium also called sodium and HPS, emit a yellowish light and are usually used for flowering plants. Sodiums are the brightest and most efficient lights and are the most popular. They are often used for flowering plants later in the plants life. The yellow hue simulates the autumn sun plants get late in the season when flowering. Sodium bulbs have a longer life span than halides.
The Horizontal Reflectors are the most popular option because they are more efficient than the vertical systems.
For growing areas smaller than 3 x 3 feet and seedlings, it may be more suitable to have a reflector with the ballast mounted inside the reflector for a cleaner look. This is usually how the 250 watt and smaller systems are sold.
If a grow room is too hot, it can severely limit the plant growth. If you are planning to have a 1000 watt light in a small closet or many lights in a bedroom, you should seriously consider an air-cooled reflector. An Air-cooled light has duct holes in the reflector to connect duct tubing and an inline fan for venting out the heat.