There are a number of factors you may want to consider when looking for the best hydroponic grow lights, such as your budget, the types of plants you want to grow, and the area you need to light. The most important factor to remember is that hydroponic grow lights need to put out a certain spectrum of light, which can be provided by a few different types of bulbs. If you plan on growing mainly leafy vegetables such as lettuce then fluorescent or metal halide lamps will typically do a good job. High pressure sodium (HPS) lights are another option that can be especially well suited if you want to grow fruiting plants such as tomatoes. You will typically want to have about 40 watts for each square foot in your hydroponic growing system, though that can differ with various types of plants.
Hydroponic grow lights are the primary light source for plants that are grown indoors in liquid based mediums. Since the plants are indoors, it is necessary to provide them with a certain spectrum of light that can support necessary biological functions. Normal incandescent light bulbs typically do not provide this spectrum, but a number of other options do. The type of light provided by different types of light bulbs is sometimes referred to by color temperature, and the desired number for most grow lights is about 5,600° Kelvin (K). Any bulb that is in that general range can be a good hydroponic grow light.
The least expensive light bulbs that can fit into the correct color temperature range are typically fluorescent. If budget is an important concern to you, then you may want to consider fluorescent hydroponic grow lights. It is important to remember that not all fluorescent bulbs output light in the 5,600 K range, so you need to check the ratings on a bulb before purchasing it. Both metal halide lamps and high pressure sodium lights can also be good grow lights, and you may want to consider an HPS bulb if you grow tomatoes or other fruiting or flowering plants.
Another factor that can help you select the best hydroponic grow lights is wattage. The necessary wattage can vary from one type of plant to another, and fruiting plants typically need more light than leafy vegetables. If you grow tomatoes then you will want a grow light that puts out about 40 watts for each square foot of growing space, so in order to choose the best lamp you will need to determine how large your growing area is. You may also want to consider the durability of a light since hydroponic systems can result in high humidity environments. A unit with an electronic ballast is necessary if you want to use an automatic light timer, but you will also need to ensure that the additional electronics do not break down in the environment created by your hydroponic system.