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High-intensity discharge, or HID, lighting is the most efficient for converting electricity into light that the average consumer can use. There are two main types of HID lighting. Metal halide bulbs produce a lot of blue light and are great primary sources of light if no natural light can be used. The average life of these bulbs is 10,000 hours; beyond that, there will be a gradual decline of light before the bulb burns out.
High-pressure sodium bulbs make an orange-red glow. This type of light is good for hormones that increase flowering and budding. This lighting is good for secondary lighting and good for greenhouse applications. HPS bulbs can and should be used up to 18,000 hours but don't have much blue light. HPS bulbs produce a lot of vertical growth. - Traditionally, fluorescent lights have been bulky and only good for seedlings. Newer technology bulbs such as compact fluorescent lightbulbs, however, work well in numbers. Fluorescent bulbs emit less heat, and more of the light is used by the plant. Because of this, the bulbs can be placed closer to the plants and less light is wasted.
- LED lights are relatively new. These lights are advertised to be very efficient and cool. Fluorescent lights, however, are cheaper and still seem to perform better than LED bulbs. LED bulbs also make the plants look a little strange.
