[jzchillin]

There are Four types of lights that are right for growing marijuana:

FLUORESCENT LIGHTS
Fluorescent bulbs are well suited for growing marijuana in the seedling & vegetative stage of growth and are also recommended for clones and mother plants. Many growers prefer the use of fluorescents during vegetative growth because of their slower pace of growth and better root development. Fluorescents fixtures such as a shoplight can be purchased at any home improvement store for under $20.
When using fluorescent bulbs try and find ones with a highest color temperature in the blue range of the spectrum (6500K). These are typically your "cool white" or "full spectrum" bulbs. Keep the tops of your plants just inches away from the fluorescent lights for best development.
Fluorescent bulbs are not good for flowering marijuana plants. They simply do not put out the lumens needed to develop meaningful buds. The light from a fluorescent bulb will not penetrate the canopy. They are also comparatively inefficient to HID (High Intensity Discharge) lights such as high pressure sodium or metal halide. 10 x 40W fluorescent bulbs consume the same amount of energy as a 400 watt HID but produce far less luminosity.

HIGH PRESSURE SODIUM LIGHTS
These are the best lights to use in flowering marijuana. They come in 250W, 400W, 430W, 600W & 1000W. The higher the wattage the larger an area the light will covert and the larger the bud development will be. These light bulbs require a ballast as they do not fit into regular sized light sockets. HPS are very efficient and put out more light with less energy than any other type of illumination available to indoor growers. HPS lighting is expensive and can range from $100 - $500 dollars in price. HPS lights, as all HID lights produce considerably more heat than standard fluorescents so attention has to be paid to not have the canopy oif your garden too close to the ligh bulb.

METAL HALIDE LIGHTS
Another kind of HID lighting is metal halide. These bulbs are recommended for vegetative growth because they operate in the blue end of the color temperature. Metal halide bulbs can also be used for flowering although the bud development will not be as big as with HPS lights.

Edit:
LED's
And yet another kind of lighting is LED's. Although I have done a considerable amount of research in this area, a small thread, like this, could not really touch on this type of lighting.



WATTAGE -- COVERAGE

For best plant developement especially during the flowering stage your garden will need approximately (Lets just say at least) 50 watts of HID lighting per square foot of illuminated area. Below is a general guide for choosing the right wattage for your garden.


A 250 watt HID will illuminate a 2' x 2' garden.
A 400 watt HID will illuminate a 3' x 3' garden.
A 600 watt HID will illuminate a 4' x 4' garden.
A 1000 watt HID will illuminate a 5' x 5' garden.


Each wattage has a limited range beyond which you do not have good light penetration. These numbers assume you have a good reflector around your bulb as well as reflective walls painted white or covered with reflective mylar. You can increase the figures a bit if using multiple bulbs. You can also increase coverage using a light mover.


A growspace that's 2 x 10 feet would require 1000 watts if you go by the 50 WPSF guideline. However a 1000W bulb only covers an area about 5 feet across meaning the edges of your garden will be dark. A better choice in this case would be three 400W or two 600W.