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HID, High Pressure Sodium (HPS) Lights for Growing Plants Indoors

High Intensity Discharge (HID) Grow Lamps
Most serious indoor growers use one or more types of High Intensity Discharge (HID) lighting, typically the Metal Halide or High Pressure Sodium lamps.

These types of lamps are most suitable for larger indoor grow operations that require a much greater amount of light.
More light can not only allow you to grow more plants, but more light will also promote more vigorous plant and fruit growth, with plants growing faster, maturing faster, producing larger fruit and flowers, and finishing faster.

Not only do HID provide a light source of much greater intensity, they are also the most efficient type of indoor grow lighting application. A 600 watt High Pressure Sodium lamp produces the same light output as fifty (50) 100 watt Incandescent bulbs, but with a fraction of the amount of energy.

The only downside is that HID light require an upfront investment, often hundreds of dollars to get setup and running. These lights require a special ballast to run the lamps, and an entry-level setup might cost $200 - $300 depending on the output, quality, and features.

Metal Halide or High Pressure Sodium?
Although both of these HID grow lights work well, the Metal Halide grow light seems to provide the plant with a better light spectrum (blue) for vigorous leaf and stem growth. On the other hand, the High Pressure Sodium lamp seems to provide the plant with a light spectrum more supportive of flower growth. It is for this reason that some more advanced growers will use the Metal Halide for the vegetative growth stage, and then later switch to the High Pressure Sodium lamp for flowering and fruit production.

New electronic ballasts allow the grower to easily alternate between the Metal Halide and High Pressure Sodium bulbs, eliminating the cost of buying separate ballasts to run the lamps, or more expensive conversion bulbs. But, many indoor gardeners are able to produce a bountiful harvest use only one type of light throughout the duration of the grow.

Most growers will favour the High Pressure Sodium lamp over the Metal Halide because it is slightly more efficient, and results in a slightly higher yield. Some growers may also start their plant’s vegetative growth under daylight colour Compact Fluorescent lights, which provide the necessary blue spectrum that supports leaf and stem growth, and then switch to the more intense High Pressure Sodium lamp once the plants are mature enough to handle the increase in light intensity.

The Mecca of grow lights is the 600w High Pressure Sodium light because it is the most efficient grow light currently available. The 600w HPS has a Lumen per Watt ratio of 150 Lumens per watt. By comparison, a 54w Compact Fluorescent (CFL) grow light, which is a very efficient light, has a Lumen per Watt ratio of 88 Lumens per watt. This makes it the most popular choice as far as indoor grow lights are concerned.