Garden Grow Lights
Garden grow lights are the key to a great indoor garden. Choosing a hydroponic light is the single-most important (and expensive) decision you will face when setting up your growspace.
There are three main types of hydroponic grow lights: Incandescent, fluorescent, and high-intensity discharge (HID). Incandescent lights are generally a poor choice for garden grow lights due to their inefficiency and limited light spectrum. HID grow lights are more efficient and produce more light (up to 10x more lumens/watt than an incandescent light), but also produce more heat, are more expensive, and will require the additional maintenance and expense of a ballast. You should be aware that HID hydroponic grow lights will be slow to warm up to their full strength. It can take up to 100 hours of burning before the light intensity and color will stabilize.
You can also use natural sunlight to grow indoors and skip the expense of purchasing garden grow lights. This can be done with a greenhouse, solar room, or even a large window that gets plenty of sunlight. You can also do the reverse of this and grow outdoors hydroponically. Hydroponics only means that the growing system is soilless, not necessarily that it is an indoor setup.
A general rule for your garden's required lighting is that 1000W will adequately penetrate about 16-25 square feet of plant area. To make your indoor gardening system more efficient, you should consider using a reflector and/or light mover. Also, don't forget that many types of hydroponic grow lighting require a ballast to ignite the bulb.
Fluorescent Garden Grow Lights
Compact fluorescent light bulbs can be used for indoor gardening, but they are not very efficient and will never produce enough light to compare to HID lighting. However, they are a popular choice for many small gardeners due to their availability, low price, compact size, and low heat emission. Because of their low heat emission and soft light intensity, fluorescent grow lights can be very effective for low-growing plants (lettuce, spinach, etc.) or plants that need indirect light (African Violets). Burning the tips should not be an issue when using compact fluorescent grow lights, so you can get the lights very close to the top of your plants.
HPS Garden Grow Lights
High Pressure Sodium bulbs have the longest life span and highest efficiency of any type of indoor lighting. The light emitted from HPS grow lights is brighter and the bulbs themselves last longer than any other type of grow lighting. Plants do not actually use the entire spectrum of the sun's light, only the red/orange and blue ranges are necessary. They are high in the red and yellow parts of the light spectrum, which simulates the fall sun. The biggest drawbacks of HPS bulbs are their high heat output and higher cost. The heat output problem can be offset with a good garden design that allows for plenty of ventilation.
Metal Halide Garden Grow Lights
The main advantage of metal halide bulbs over high pressure sodium grow lights is the full spectrum light they produce. Their blue light is closest to the summer sun and is best for vegetating plants. Advances in technology have led to specialized bulbs that produce only a certain range of the light spectrum. More specific combinations of metal halides are used to ensure that the bulb will only emit a particular color of light.
Metal halide garden grow lights work best for leafy crops like lettuce or spinach because they are so high in cool spectrum light (blue). This encourages tight, compact growth and lots of leaf development, but flowering will be limited.