There are several options when it comes to artificial light for orchids. Orchids need certain kinds of light in order to grow well and bloom. They also need enough of this light. Normal incandescent bulbs may look bright, but they are the least efficient source of lighting for plants. This is because they consume a lot of power and put out a lot of heat energy, but produce very little light that is useful for plants. Florescent light is far better in terms of the amount of usable light energy produced versus the amount of power used and the amount of heat produced. For most hobbyist and household orchid growers florescent light will be the most logical choice. One of the options for lighting is Metal Halide and High Pressure Sodium fixtures. These can be good choices for someone who has a lot of orchids, or a number of large orchids. MH and HPS fixtures put out a lot of light, but also produce a lot of heat. They can be very expensive and need to be housed in a specially designed casing with a ballast. They also tend to suck a lot of power and can be expensive to run.
Best Artificial Orchid Lighting Set-ups, Pros and Cons
Florescent Fixtures: These are the most practical choice for most home growers. They are efficient, but still need to be used in an effective way. There are essentially two options. Compact florescent bulbs can be used by themselves in order to light a few plants. Otherwise, tubes can be used, but for most orchids two to four tubes will be necessary. Orchids that need greater light should be grown closer to (almost touching the tubes), those that need less can be grown farther away. Generally you will need to buy broad spectrum, or full spectrum bulbs, in order for them to be effective. These also will not work for tall orchids (because the light will not reach the lower parts of the plant), or very high light orchids, such as most Vandas. Florescent light can be highly economical and does not produce a lot of heat.
High Pressure Sodium Fixtures: These are the most effective lights for growing over a large area. They put out a lot of light, but also use a lot of energy. I have a 250 Watt HPS system and this allows me to grow orchids over approximately a five foot area. The fixture should generally be hung two to four feet above the plants. There are three drawbacks to these systems: They produce a lot of heat, they are expensive to run and the light they put out is in the red spectrum, so it does not look quite natural. This red light tends to encourage flowering, but can cause strange plant growth. They are also complicated to install and can be unsafe. The two most reputable companies that produce these fixtures are Sun System and Hydro Farm. If not properly installed these can be a fire hazard, so make sure yours is UL listed. They also tend to be at least $200 for a new system.
Metal Halide: These fixtures are a lot like the HPS ones, but the light appears more natural because it is further in the blue spectrum. This light also encourages healthier plant growth.