These are the same powerful lights used by professional greenhouse growers. HID lights are highly energy efficient. You can grow any plant, anywhere, anytime you choose. The “high intensity” light energy is effective much farther than fluorescent:

250 watt/3 ft., 400 watt/5 ft., 600 watt/6 ft. The 400 watt is recommended for most hobby greenhouse applications.

HID Types:

• High Pressures Sodium (HPS)
  This light has extra output in the yellow, orange and red spectrum, which increases flower quality, size and fruiting. It is the best choice for use in a greenhouse.
  
  
• Metal Halide (MH)
  A full light spectrum is the advantage of MH. It is the most effective light for use indoors where there is limited sunlight.

Fluorescent Lights

These lights are recommended for starting seedlings and cuttings. They are also popular for growing herbs and other low-light plants like African violets. Fluorescent lights are “low intensity” and need to be within 6" to 8" of the plants to be effective.