Choosing lighting for an environment requires many considerations. The light needs of your crop is most important but you have to consider the heat the lights produce and your ability to cool lights. The size of your area also is important to consider. When lighting a large area the number of lights required can inflate your costs dramatically, so using less more powerful lights can bring down your set up costs.
The classic choice for indoor lighting for many years. HID stands for high intensity discharge. This lighting consists of Metal Halide or High Pressure Sodium bulbs. Metal Halide lamps put off a blue spectrum which helps to simulate the light in the early growing season. High pressure sodium lights are deep red in color and simulate the late fall when the sun is lower in the horizon. This red light aids in flower production. Older magnetic ballasts were sometimes dedicated to running only one bulb type, and at a specific wattage, so make sure you know what you are plugging in. A typical thousand watt light will be anywhere from 16” to 24” from the canopy to prevent any light bleaching or burning. Newer digital ballasts are more efficient than older magnetic coil ballasts and will automatically switch between using high pressure sodium and metal halide bulbs. These lights are available in a single, or double ended configuration. Double ended lighting offers the greatest intensity, but they often require more canopy clearance.
Light Emitting Ceramics
One of the newest technologies in lighting to catch on. These lights show real promise when compared to HID lighting because of their high relative efficiency. Although the footprint of a 315 watt light may only be 3x3 for flowering, the quality of the light is much better, and with less power. These units are available with a 4k vegetative bulb, or a 3k flowering bulb. These lights produce the closest to sunlight spectrum of light for your plants at low heat and low wattage.
A lower power option when compared to HID lighting. These lights have the disadvantage of having low penetration through a plant canopy, meaning to be most effective plants should be short or at least not have a canopy deeper than a few inches. These lights are most effective when just a few inches above the plant. This means that lighting a large space with fluorescent lights can be very expensive. This is why many people prefer using them for seedlings and early vegetative growth.
These compact and high efficiency lights have become popular in recent years. Not all Led manufactures are the same, but Companies like Black Dog and California Lightworks both offer a wide selection of wattages to suit a variety of footprints. These lights offer a tuned spectrum that is ideal for growing plants.