Choosing a hydroponic light system might seem easy enough at first glance, but any experienced plant lover and gardener will know that's not really the case. There are quite a few factors that can make the difference between an awful and a quality light system and if you have the pockets to cover the expenses, you should always try to get the solution that satisfies most, if not all of the following requirements.
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Hydroponic Light Systems - Luminosity
When you buy a room light, or a lamp, you simply judge its quality by the luminosity it can shine with. After all, the higher the luminosity, the better you will be able to see your way around the house. With hydroponic light systems however, things are a little different. Plants don't necessarily need a lot of light, because they can't "see". They use the light for completely different purposes, such as photosynthesis. So don't simply be fooled by the power output of a hydroponic light, there are other factors that need to be considered as well.
Hydroponic Light Systems - Survivability
The greenhouse is a tough place to live in and operate for a hydroponic light system. High temperatures, high humidity and all sorts of bugs and pests can make the lamp's job a lot harder and cause it to breakdown or not function to its full capacity over time. That's why you need to choose a hydroponic light system that has good protection against all these problems and one that can withstand a fair share of beating from them.
Overlooking this aspect has caused some severe problems in the past and there's no guarantee it couldn't happen to you. There are dozens of ways your poorly wired, unprotected hydroponics light system can go down and a short circuit, or a high pressure sodium lamp exploding in your greenhouse will endanger not only your plants, but possibly your life and that of those around you!
Hydroponic Light System - Light Spectrum
Sunlight is a combination of various temperature colors, so plants are used to naturally getting different light spectrums to grow. Most hydroponic lights try to copy these spectrums and color temperatures. For example, mercury-base lamps will glow blueish, simulating a cloudy afternoon or a starry night, high pressure sodium (HPS) will glow orange simulating sunrise and dusk and metal halide lamps can simulate intense afternoon sunlight with their pure white. Depending on the plant's photocycle and the type of light it's used to getting in its natural environment, some of these light spectrums might produce better results than others. If you're unsure what hydroponic light system would be better suited for your plants, try out a few different lamps and color temperatures to actually test how your plants react to them.
Obviously, these aren't the only factors you'll want to take into consideration when choosing a hydroponics light system, but these three should be on top of your priority list. Sometimes and with some plants, you could just pull it off by lighting your hydroponic gardening system randomly and with the first lamps that fall in your hand. However, if you want to offer your plants the best artificial conditions (ones that will often surpass the lighting conditions offered by nature), then being picky about your hydroponics light system is the way to go.