Hey Jon,
http://www.greenhousecatalog.com/grow-lights
Using a grow light is a great way to boost plant growth and to extend your growing seasons. Many plants have requirements for light that may not be met without supplemental lighting, depending on your location and the season. You should consider a grow light if you want to actively grow in the winter, especially if you live in a particularly cloudy area or if you have exceptionally short days (most plants like about twelve hours of light.) Without sufficient light, plants are not able to adequately photosynthesize and they will not mature properly. There are several types of grow lights available, each produce specialized types of light that will benefit your plants in different ways at different stages in their lives. You can find a complete listing of all available grow lights.
Fluorescent Grow Lights
These grow lights emit a soft white full spectrum of light. The are very energy-efficient and inexpensive to operate. Fluorescent lights work best placed directly over seedlings that need extra light to stimulate growth. Fluorescent lights have a short range of effectiveness, the lights need to be within a few inches from the plants canopy. Fortunately, fluorescent lights put out very low heat which allows you to put the light within inches above the plant.
T-5 Fluorescent Grow Lights 
Use less energy and provide a more intense light than there fluorescent cousins. T-5 full spectrum lamps are superior to other fluorescent lamps because they are thinner, lighter and more efficient, and capable of producing greater light intensity. One T-5 high output lamp produces virtually double the light output as other fluorescent lamps. T-5 lights should be place a few inches from the top of your plants like the fluorescent lights.
Metal Halide Grow Lights
These systems emit the violet and blue portions of the sun’s spectrum. This is the kind of light that is found during springtime. As a result, the plants these lights help the plants develop a compact green growth, a stronger root system and are consequently more disease-resistant. For that reason, metal halide light is best for starting plants and supporting them while they are in early development. An advantage of this system is that you can buy one grow light to cover a large growing area. It is not necessary to place the light close to the plants. In fact, Metal Halide lights do give off some heat so you want to keep the plants at a distance to keep plants from burning. The extra heat can be a nice way to provide some extra warmth in your greenhouse during the winter. Over time, Metal Halide bulbs get weaker and need to be replaced, the average lifespan is about 10,000 cumulative hours.
For metal halide or high-pressure sodium lights (which produce a much more intense light than fluorescent lights), a 400 Watt bulb is best used for approximately a 4' x 4' area, but it will give some coverage to an 8' x 8' greenhouse. If your plants require lots of light or if you have a larger greenhouse, a 1000 Watt bulb is more appropriate for that area. If you do not see the wattage you are looking for on our website, be sure to contact us so that we may special order the proper bulb for you.
High-Pressure Sodium Lights
These systems produce more of the orange and red spectrum. This light naturally occurs during late summer and fall and encourages flower production, fruiting and ripening. Therefore, this light is best for plants that are more mature and in production. An advantage of this system is that you can buy one grow light to cover a large growing area. It is not necessary to place the light close to the plants. In fact, High-Pressure Sodium lights do give off some heat so you want to hang the fixtures 3 to 4 feet above the plants to keep plants from burning. The extra heat can be a nice way to provide some extra warmth in your greenhouse during the winter. Over time, High Pressure Sodium bulbs get weaker and need to be replaced.the average lifespan is about 18,000 cumulative hours.
For metal halide or high-pressure sodium lights (which produce a much more intense light than fluorescent lights), a 400 Watt bulb is best used for approximately a 4' x 4' area, but it will give some coverage to an 8' x 8' greenhouse. If your plants require lots of light or if you have a larger greenhouse, a 1000 Watt bulb is more appropriate for that area. If you do not see the wattage you are looking for on our website, be sure to contact us so that we may special order the proper bulb for you.
LED Grow Lights 
LED grow lights are the newest type of light on the market. LED lights are the most economical to run. They take a little bit of getting used to. When on, they produce a pink light and the plants look a bit on the pink side. When you turn them off, you can see the wonderful green of your plants. These lights work great and we highly recommend them. LED lights are recommended to be placed about 12 inches from the plant canopy. They give off very little heat and the bulbs have a very long life cycle. One big plus with LED lights is there is no mercury (as in fluorescent lights), so they are safe to recycle.
Incandescent Grow Lights
Incandescent grow lights are best suited to highlight or showcase a plant. They are not as energy efficient nor do they provide very rich light. Look for full spectrum lights specifically designed as a grow light. These spot lights get hot, so place at a safe distance from your plant.