Answering your questions about LED Grow Lights:
An article by Pete Bunner, CEO of The LED Store, Copyright 2009
Light emitting diode (LED) lighting sources assist in the growing of plants indoors because of their basic electronic structure can be engineered to provide the exact lighting spectrum needed to optimize the growth and flowering of plants. This spectrum of blue, orange and red was originally developed by NASA to efficiently grow plants on the international space station. The engineers of NASA needed to invent a lighting source that was super efficient (used less electricity), produced a low amount of heat and produced the exact bandwidth for plants to grow and produce food. Astronauts needed to produce their own food because of some of the long stays on the ISS and for research in sustainable food production on trips to other planets. Another interesting fact about LED Lighting is that one of the world’s largest lighting manufacturers has stopped all research and development into any other light sources except solid state lighting which is the category LED lights are in. This company alone is investing 5% of their current revenues into research in solid state lighting. In my opinion, you can safely conclude that LED lighting is here to stay. Actually, most lighting industry experts are confident that LED Lighting will begin to replace all other lighting sources including compact fluorescents. Here are some facts about utilizing this light source to grow plants of all types.  
• What is a LED Grow Light? As an example: low wattage LED lights have been used as power indicator lights for years on most electronic equipment, in pocket flashlights and of course for LED televisions screens. A LED Grow Light uses higher power LED’s packed closely together in rows to produce an intense light source. These particular LED’s produce light bandwidths that are conducive for plant growth and thus the name.
• In general a 90 watt “UFO” LED Grow Light can replace a 300 watt conventional bulb and 600 watt LED grow light panel can replace about 1800 watts of conventional light source per industry advocates. Sizing LED Grow Lighting for your grow area should be discussed with your distributor or retailer. Plant type, room size, other lighting sources and budget are all factors to be considered before purchasing. When talking with your supplier ask for light coverage specifications or a lighting coverage design before you purchase a grow light. Any reputable distributor or retailer should be able to do this for you. If you are a commercial grower this lighting design can be very helpful in assisting you determine return on investment.
• The LED Grow Lights can be placed closer to the plants because of the low heat that the fixture produces. Always, move your lights closer slowly (over days) and check your plants regularly for any type of heat stress.
• LED Grow Lights are very efficient in transforming electricity into light. This means that LED’s use up to 80% of the energy used to create light. In comparison, incandescent lights efficiency is at around 5%. This efficiency produces less heat and a high watt to lumen ratio.
• As an example: A 600 watt LED grow light can replace up to 1800 watts of high intensity discharge lighting (e.g.: HPS & MH lights) per testing by manufacturers.
• Most other legacy lighting sources produce a broad spectrum of light that a plant does not use efficiently. Legacy types of grow lights do have a more focused spectrum but produce a lighting spectrum that goes into the ultraviolet (UV) spectrum which can be harmful to plants and people. LED’s produce low or no UV light because how the light is manufactured.
• “LED Grow Lights produce light at the exact bandwidth that lights need”. What does that mean? The light spectrum which on a grand scale starts at Gamma rays and goes through to Radio waves. Visible light (please see chart below) has a spectrum of 380 nanometers to 740 nanometers (nm) approximately. Plants need certain “frequencies” of light for growth. These frequencies are blue at 460nm, orange at 620nm and red at 660nm. The reason light is measured in nanometers is based simply on the length of the wavelength of each color as seen above. Light is not only visible light in Physics but all types of energy such as x-rays and radio waves. When trying to picture this think of a dial radio and the process of finding a station you like by tuning via knob. Your favorite stations for growing plants are at 460, 620 and 660 nanometers on the visible light radio. Individual LED’s are manufactured to produce a specific bandwidth of light and this is what makes it possible to combine different color ratios of LED’s to grow plants.
• The ratio used in most LED Grow Lights is 7 red LED’s, 1 blue LED and 1 orange LED. The light is usually manufactured in multiples of this ratio. Custom lights are available and are usually for applications that need additional blue LED’s for the growth cycle of certain plants.
• Blue LED lights are also used in treating people with certain medical conditions such as psoriasis, acne and seasonal affective disorder. Actually, there is a growing industry in Europe utilizing LED’s to treat people’s skin for the effects of aging on the skin and as a safer alternative to tanning.
• Light source and beam direction of a LED is unique. A standard bulb heats a filament and or gas to create light. This type of lighting goes in all directions making the use of hoods and reflectors necessary to direct the light to the plants to use. LED lights produce a directional cone of light that sends light in a measurable direction. This adds to the efficiency that is claimed and is the reason LED lights for growing plants set on a flat panel. The average angle of light coming from a LED grow light is 120 degrees compared to 360 degrees in conventional lighting.
• Watering has to be adjusted with LED Grow Lights because the soil is not being “baked” by lights that produce high heat amounts. We suggest at least using an inexpensive soil dampness meter if you are growing in soil. If possible monitor before changing to LED Grow Lights so you have a baseline for your water use. Hydroponic growers will also see less water used also but this level is easier managed because of the centralized water/nutrient source.
• Along with watering be watchful of nutrients levels given to the plants under LED Grow Lights. The environment is gentler and may cause the use of fewer nutrients by the plants to achieve the same amount of growth.
• Environmental conditioning needs to be adjusted because the heat created by LED lighting is less than conventional grow lighting. Room temperature for proper plant growth needs to be a in a certain range for the plants you choose to grow. As a general rule plants optimally grow and flower at temperatures between 68F to 86F.
• Conventional plant lighting creates high temperature zones under the hood which will burn leaves and flowers if the plant is placed too close to the bulb. LED’s have a lower heat signature and thus are less likely to burn leaves.
• Air movement and air transfer in your grow space is still very important. Plants utilize carbon dioxide for photosynthesis and this can be easily provided by supplying fresh air to your plants.  “Stale” air in a green house or indoor growing garden decreases the ability of your vegetables and or flowers to produce food and in turn grow to their potential. LED Lights are fully compatible if you are currently using a carbon dioxide production system to assist in plant growth.
• The gentler environment while using LED Lights may mean initially observing and adjusting humidity levels in your indoor gardening area. The lower amounts of heat produced by LED Grow Lights are the reason for this humidity fluctuation.
• To maximize your light penetration, try growing several small plants rather than a few large ones. Plants that have the correct nutrition, water and light do not have to be large to produce fruit and flowers. Efficient absorption of these resources is much more important for maximum yield.
• Photo period is the length of time a grow light is turned on. This is up to debate but based on several independent tests, plants under LED Grow Lights need less of a photo period. As a general rule the growth period of a plant is always longer than the flowering period but both can be shortened by an equal percentage. We suggest using a test group of plants to start. Depending on what plant you are growing will be the determination on the length of the photo period. Always allow your plants to have a period of total darkness within this cycle. This “rest” and “absorption” period will actually lead to faster growing, healthier plants.
• The minimum heat produced by LED’s and efficient use electricity will allow people living in small homes, offices or apartments easier access the indoor gardening world. These same growers can grow large amounts of organic food affordably all year long without concerns of climate or available outdoor space. This can be achieved with a little ingenuity in a closet, bedroom and basement.
• Lifespan of the LED light is approximately 50,000 hours which is 3 to 10 times the lifespan of conventional legacy lighting. The average LED that is on 14 hours a day will last over 9 years. The energy savings alone is a great reason to switch to LED lighting but the fact that conventional lighting sources will need replaced 2 to 9 times is another factor to consider. LED’s do have a slight light degradation at rates similar to every other light source but actual effects on plant growth productivity happens in the last few years of service. I suggest moving these “older” lights to rooms that are used for cloning, seedling and growth stages. Usually these rooms need less light intensity than plant flowering/fruiting areas .
• Compact florescent and other legacy lighting sources use mercury gases that require special waste removal to a hazardous material removal facility. Caution also needs to be used if breakage occurs of with these type of lighting because the clean up if handled per EPA standards can be very expensive.
• Technical concerns are few because all available LED Grow Lights utilize a standard 110 volt outlet and need less amperage than other lighting sources. Conventional legacy lighting sources may need a special high voltage 220 volt outlet(s). Loading of electrical circuits should always be reviewed and installed by a licensed electrician because of safety concerns of overloading these circuits. Be safe and remember that any type of grow light will be on run for at least 12 hours a day and much of this time you will not be present in the area and or room. As with any electrical appliance do not install in an area that could water could come in contact with the fixture.
• LED’s are solid state lighting sources which have no moving parts or filaments that can break or burn out. Solid State lighting designs for most grow lights entail attaching the individual LED’s on printed circuit boards in closely packed rows. This is the same technology used in most other electronic devices and has been proved for years.
• LED Grow Lights do not have ballasts. The LED light is a self enclosed lighting fixture and simply needs hung over the plants and plugged into a standard outlet. Larger wattage conventional lighting can utilize remote ballast which transforms the input voltage into a usable voltage for the particular lamp you are using. These need mounted near the light (or are attached) and entail installing 220 volt outlets near your grow area.
• LED Grow Lights are very quiet compared to high voltage lighting sources. Multiple lighting configurations of legacy lighting can create a signatory “hum” into the growing area. LED Grow Lights virtually eliminate this noise.
• Costs of operating LED Grow Lights can be one third the cost of conventional lighting. If you compare energy usage over a year the additional cost for a LED Grow Light becomes null. As an example: after the first year a 600 watt LED Grow Light can save you 600.00 to 800.00 dollars a year. This can add up to a great deal of money for those of you that run multiple lights. The current additional proposed taxes such as Cap and Trade on energy production will equal even larger electrical bills.
• Using LED’s as supplementary lighting can also work very well. People that own legacy lighting systems and need to expand their growing square footage should try adding LED lighting instead of buying an additional standard light. The savings are still present and the ability to test LED’s while using your current system is an ideal way to transition slowly to the new lighting source. We also suggest starting in your clone or seedling area because of the way these lights are gentle on plants.
• Throughout Europe and Asia LED’s are used in greenhouses to provide additional lighting to plants. The properties explained allow for lower electrical bills and lower cooling bills if air conditioning is used. Most importantly LED lights are helping growers of all sizes to produce flowers, fruits and vegetables in an economical manner. This means more dollars to the bottom line.

In conclusion: Growing plants is a balance of all the variables listed along with proper and correctly timed nutrition which we did not go into detail about. If you are a veteran gardener this is already known but if you are new to this fascinating world of greenhouse or indoor gardening do not get overwhelmed. Achieving this balance of growth factors is the fun part and should not be stressful. Growing healthy and beautiful plants will be the outcome of patiently adjusting all of these parameters. LED Grow Lights will be a part of this goal and are fast becoming a “green” lighting alternative for the greenhouse operator, retailers and individual home gardeners.

About the author: Pete Bunner is President of The LED Store (www.smartlightingshop.com) and owner of Bunner Tree Farm in Richmond, Ohio. Pete has been in the technology field for twenty years and has founded several other businesses. He can be reached at led@smartlightingshop.com or by phone at 740-765-5442.