Fluorescent lights are a popular choice among small gardeners due to their low price, availability, compact size, low heat emission, and smaller electric bills.
Fluorescent bulbs are not ideal for large plants, as they do not penetrate as deeply as High Intensity Discharge lamps. Fluorescent lamps may be a viable option for growing large plants only if you have lights above and to the side of the plant.
Due to their low heat emission and soft light intensity, fluorescent grow lights are effective for low-growing plants (lettuce, spinach, cabbage, strawberries etc.) or plants that need indirect light such as African Violets.
Some growers find that fluorescent lights are perfect for use with seedlings and cuttings as well as for use with other plants that do not require the high intensity of H.I.D. (High Intensity Discharge) lighting.
Compact Fluorescent Lamps (CFL) are a relatively new form of fluorescent bulb. They include those spiral shaped energy efficient light-bulbs which are quickly replacing incandescent bulbs for household lighting. They are cost effective and useful for smaller hydroponic projects. They don't require professional wiring or a ballast, simply a socket to screw them into - same as incandescent in that respect.
One drawback to Compact Fluorescent is that their light is not directed - it is emitted in all directions. A reflector or reflective material such as mylar would be advantageous.
H.I.D. lights are the undoubtedly the best grow lights available today. There are two types of H.I.D. (High Intensity Discharge) lamps that have suitable spectrum's and intensity for plant growth.
1.] MH (Metal Halide) Emit a blue light spectrum, similar to the Summer sun.
2.] HPS (High Pressure Sodium) Emit a red/yellow spectrum similar to the Autumn sun.
Metal Halide - MH bulbs are highly efficient, they produce between 70 and 115 lumens of light output per watt of electricity used. MH (Metal Halide) Their blue spectrum emission promotes rapid plant growth. They also promote compact plants with shorter inter-nodal foliage spacing.
The average lifespan of an MH bulb is approximately 10,000 cumulative hours. The bulb will light up beyond this point but due to the gradual decline of light, will become increasingly ineffective.
If you compare their lumen (brightness) per unit of energy consumed, metal halides produce up to 125 lumens per watt compared to 39 lumens per watt with standard fluorescent lights and 18 lumens per watt for standard incandescent bulbs.
MH (Medal Halide) bulbs should be replaced about every 10,000 hours of use or approximately 18 months (as per an 18 hour / day on cycle).
The bulbs themselves need to be burned in a specific position. They come in three types: Vertical (marked BU or BD), Horizontal (marked HOR) and Universal (marked U). The universal bulbs can be burned in any position, but they still are more efficient when burned vertically.
High pressure Sodium Bulbs emit an orange-red glow. This band of light triggers plant hormones that increase flowering and budding. They are the best grow lights available for secondary or supplemental lighting (used in conjunction with natural sunlight). This is ideal for greenhouse growing applications.
Not only is this a great flowering light, it has two features that make it a more economical choice. Their average lifespan is twice that of metal halides.
HOWEVER,and that's a big however - after roughly 18,000 hours of use, High pressure Sodium Bulbs will start to draw more electricity than their rated watts while gradually producing less light. HPS bulbs can be highly efficient. They produce up to 140 lumens per watt. Their disadvantage is they are deficient in the blue spectrum and their diminished lifespan.
If a gardener were to start a young plant under a HPS bulb, she/he would see impressive vertical growth. In fact, probably too impressive. Most plants would grow up thin and lanky and in no time you will have to prune your plant back before it grows into the light fixture. The exception to this is using HPS grow lights in a greenhouse or in conjunction another light source that emits light in the blue spectrum. Light sources that have a high output in the blue spectrum like sunlight and MH grow lights offset any stretching caused by HPS bulbs.
For plants that normally bud and flower in the fall an HPS (High Pressure Sodium) is usually the light of choice because it's light spectrum promotes flower production.
There are also color corrected HPS (High Pressure Sodium) bulbs available for improved growing efficiency. These are designed specifically for indoor horticulture, and have a more balanced color spectrum.
HPS bulbs should be changed no later than 24 months from initial use. These bulbs (like the Metal Halides) also slowly decrease in brightness and hence lose efficiency over time, in order to maintain the proper light intensity these bulbs should be changed at the end of their rated life.
I personally haven't used LED lights (Light Emitting Diodes) extensively yet, I'm having great success without them. Many people swear by them however. A 90 watt LED light system has the same output power as a 400 watt HPS or MH bulb. They are advertised as the most efficient and coolest running grow lights available. LED grow lights are not recommended for use with ornamental plants as they give plants an unnatural sickly appearance when the light is on.
LEDs are cost effective, they use much less electricity than any other light source. Their longevity is also unparalleled, rated at about 50,000 hours, although some manufacturers are claiming 100,000 for newer versions.
Newer Fluorescent lighting, although they use about 40% less energy than older versions, are still only rated at a maximum of 30,000 hours, Compact fluorescent lamps with a maximum of around 15,000.
Contemporary LEDs produce light in a wider spectrum than the earlier versions with temperatures comparable to fluorescent lights, however the LEDs don't have the flickering issues experienced by Florescent - particularly as they age.
Traditionally, in hydroponics plants requiring high intensity light have been nurtured under HID / HPS Lighting.
The best fluorescent lights available can not compare to the yields achieved with HID lights. The LED industry is trying to make a case for their product - that it achieves results comparable to High Intensity Lighting. This is unproven as of yet.
HID lights have lower upfront cost, but do require more maintainence than LEDs. LEDs have a relatively high upfront cost.
Conversion lamps are HPS lamps that are operated with standard metal halide ballasts. Enhanced Spectrum Lamps are top rated horticultural lamps due to their increased output in the Blue spectrum, giving the best combination of light for both growth, and flowering. They are also a variety of HPS.
Due to the heat that is emitted from these types of fixtures, you should hang them according to size. Smaller wattage systems (100 and 250) should be hung about 2 to 3 feet from the top of the plants. Medium wattage systems (400 and 600) should be hung around 4 feet from the top of the plants. High wattage systems (1000 and up) should be placed at least 4 to 6 feet from the plant tops.
Day / Night Cycle.
Plants need the darkness as well as sunlight, so do not leave your Hydroponic / Horticultural lights running 24/7 . The lights run time depends on the variety of plant. Most ornamental plants and vegetables need about 10 to 12 hours of light to promote healthy growth. Plants that produce fruits or flowers will show improvement with up to 16 hours a day of supplemental light.
Operating Cost for Hydroponic Lighting Systems
To calculate the cost of operating a Lighting System ,take the lights combined wattage, and divide it by 1000 to get the kilowatts used. Then multiply that number by the amount your electric company charges per kilowatt hour. HID lights will use the number of watts it emits per hour, ie; 600w system will use 600 watts per hour (regardless of spectrum).
(light wattage output / 1000) x electricity cost per kilowatt hour = Operating cost per hour operating cost per hour x hours used per month = Operating cost per month
Use of Reflectors in Hydroponic and Indoor Grow light Systems.
The type and style of reflector used can make a tremendous difference in growing results ! Most reflectors come with a 85 -95% reflective, textured aluminum insert or a reflective spectral pebble insert.
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 soil-less, not necessarily that it is an indoor setup.