Frequently Asked Questions - Horticultural Lighting

Lighting Basics
Artificial Light is critical for indoor plant growth There are 3 basic choices for artificial light:

Incandescent lamps - These are the standard "light bulbs" that are used by everyone for general household lighting. These are very inefficient light sources and use a lot of energy to produce just a little light.
Fluorescent lamps -The fluorescent lamps is starting to grow in popularity for indoor plant growth, especially "High-Output" T5 fluorescent lamps. Fluorescent lamps are 3-7 times more efficient than incandescent lamps.
HID lamps - These include Metal Halide and High Pressure Sodium lighting sources, traditionally used for lighting large areas such as factories, warehouses and parking lots, they are also the primary choice for indoor plant growth. HID lamps are 4-8 times more efficient than incandescent lamps.

Lighting for Plants
Light is seen by people as "visible energy" that we use to see and distinguish different colors. Plants use light as stimulants and fuel for growth. Light is the most important factor in any indoor growing environment. It is also the limiting factor in any indoor growing environment. Lighting technology has vastly improved over what it once was and it is continually evolving with new technologies. Without good and plentiful light, a plant will not be able to perform photosynthesis, chiefly the main principle by which a plant converts food into energy. Plants are able to use artificial light, so long as it is of the correct lighting spectrum for plant growth and there is plenty of it. An indoor garden requires a lot of light and an efficient and effective source should be chosen to provide this light. Some types of incandescent lamps might be an effective source for plant growth but they are not very efficient and many lamps and a lot of energy (watts) would be needed. Most indoor gardens are lighted by HID lamps (Metal Halide or High Pressure Sodium), because these sources are both effective and efficient, producing much more light per watt of energy used than incandescent lamps. Fluorescent lamps are often used for seed starting and early stages of plant growth or to supplement spectral needs of plants when using HPS lamps. Different HID and Fluorescent lamps produce different lighting spectrums and lumen outputs.

What are "lighting spectrums"?
Different types of lamps produce different lighting "spectrums". The visible lighting spectrum is much like a rainbow, ranging in order from violet-blue-green-yellow-orange-red. This spectrum is scientifically measured in "degrees Kelvin" or "K". A lamp that is rated at 6500 Kelvin or 6500K would appear to be "blue-ish", while a lamp that is rated at 2,200K would appear to be "orange-red-ish". Plants are under the spell of the seasons, thus subject to seasonal changes in available light spectrum. The blue end of the spectrum is associated with spring and it's lengthening days, promoting vegetative growth in most plants. The red end of the spectrum is reminiscent of autumn, with its shortening days and long harvest sunset. Autumn usually promotes a higher flower-to-leaf ratio in flowering plants. It is generally accepted that an indoor grower should use either a Metal Halide (MH), or High Pressure Sodium (HPS) light. The difference between the two types of lights is basically the "light spectrum" that they produce. Plants respond to different light spectrums in different ways. Additionally, in different stages of the plant growth, a plant will respond better to different spectrums. MH lamps are typically used for vegetative plants or for plants in the vegetative stage of growth while HPS lamps are used for flowering plants or for plants in the flowering stage of growth. There are countless books and websites, many with lighting advice for specific plants. We offer all types of lighting systems and many types of "conversion" lamps which allow you to purchase a standard HPS system and simply screw in an HPS conversion bulb when you plant enters the flowering stage of growth.

What is a "lumen" and why do I need them?
Growing plants indoors requires a lot of light. Lumens are a scientific term for measuring the visible output of a lamp (or "light bulb" or "bulb"). A standard 60 watt incandescent lamp is rated at an output of 900 lumens. A 400 watt Metal Halide lamp produces 36,000 lumens and a 400 watt High Pressure Sodium lamp produces 50,000 lumens. Generally High Pressure Sodium lamps are more efficient light producers (more lumens per watt), these lamps produce a range of 100-140 lumens per watt, while Metal Halide lamps produce a range of 70-110 lumens per watt.

What is a "footcandle" and why do I need them?
A footcandle is a measure of light intensity. While a lamp (the source of the light energy) produces lumens, footcandles (fc) are measured light intensity at a certain point. A footcandle is scientifically, a unit of measure of the intensity of light falling on a surface, equal to one lumen per square foot and originally defined with reference to a candle burning at one foot from a given surface. Since light intensity is the primary factor in the photosynthesis of plants, horticulturalists often measure and discuss optimum intensity for various plants in foot-candles. Full, unobstructed sunlight has an intensity of approximately 10,000 fc. An overcast day will produce an intensity of around 1,000 fc. The intensity of light near a window can range from 100 to 5,000 fc, depending on the orientation of the window, time of year and latitude. Footcandle measurements will decrease rapidly as the light source is moved further away from your plants.

What are the different parts of my indoor garden lighting system?
Your lighting system will have 3 basic parts, the ballast, the reflector and the lamp.

What is a ballast and why do I need one?
The ballast is the electrical component of a High Intensity Discharge (H.I.D.) or Fluorescent light that makes it work. The ballast is necessary to operate a H.I.D. or Fluorescent light. It converts the electricity from your home into the specific energy frequency needed to operate the lamp. Each specific H.I.D. lamp type (High Pressure Sodium [HPS], Metal Halide [MH], etc.) and wattage type (150, 250, 400, 600, 1000, etc.) have a specific ballast for each type and wattage of H.I.D. lamp. They are not compatible with each other, you cannot use different lamp types or wattages in your light other than the one specifically made for it. The only exception is using a "Conversion" lamp which is made to operate in a specific fixture. The ballast will typically have a power cord which plugs into your wall outlet. The ballast will also have an output receptacle or output cord which attached to the socket for your lamp. What is a reflector and why do I need one? Reflectors (also known as: hoods, shades, fixtures, etc), serve the purpose of directing the light output from your lamp towards your garden. The reflector may serve as an enclosure for your lamp, and if equipped with a glass lens, will reduce the heat directed toward your garden. Additionally, if the reflector is equipped with cooling flanges, the reflector may be "air-cooled" with the help of a fan, and most of the heat created by your lighting system may be carried away from you garden via this air cooling method. A well designed and constructed reflector will dramatically increase your indoor garden yields while a poorly designed reflector will rob your indoor garden of the precious lumens it needs for maximum growth. ALWAYS, use a Horizontal reflector, as "Vertical and Vertizontal" reflectors are very inefficient. ALWAYS use a reflector with "spectral pebbled aluminum inserts" as these dramatically improve the performance of your reflector.

High Pressure Sodium and Metal Halide; what is the difference?
Although High Pressure Sodium and Metal Halide are both types of HID (High Intensity Discharge) lights, they emit different color spectrums. Generally High Pressure Sodium (HPS) lamps emit light that is concentrated in the red to yellow side of the spectrum and weak in the blue-violet end. Metal Halide (MH) lamps, by contrast, emit a more balanced light, but are generally concentrated in the blue to yellow side of the spectrum and are weak in the orange to read end. Both types of lighting have their place in an indoor growing environment. Another difference is the lumens per watt of both bulbs. HPS lamps are usually more efficient light producers (more lumens per watt), these lamps produce a range of 100-140 lumens per watt, while MH lamps produce a range of 70-110 lumens per watt. An easy way to tell difference between the two types is by appearance. Generally HPS lamps appear very yellow-orange, MH lamps appear more blue-white

Can I use a HPS lamp in a MH system? And visa-versa?
Generally, NO! With very few exceptions and HPS lamp must be used only with HPS type ballasts and additionally a MH lamp must be used with an MH ballast. The only exceptions are specially designed "conversion" bulbs and a few "switchable" type ballasts.

Can I use a 1000watt lamp with my 600 watt ballast?
NO! You must use the specific wattage lamp to match the ballast. Although other wattage lamps may "operate" on other wattage ballasts, a non-matching ballast will either quickly cause the lamp to fail or produce only a fraction of the light output the lamp was intended to provide.

What is a "CONVERSION" lamp and why should I use one?
A "conversion" lamp is a specially designed and constructed lamp that allows operation of a HPS lamp type with a MH ballast type or an MH lamp type with a HPS ballast type. These lamps, while once unreliable and expensive, now have become very dependable in quality and performance and the price is very reasonable. They serve the purpose of improving yields for indoor growers who have only one type of lighting systems for their garden. For example, suppose an indoor gardener has purchased a HPS lighting system. They may also use a Metal Halide Conversion lamp for the vegetative growth cycle of the garden and then switch to the HPS light for flowering/fruiting phase of growth. This is a very popular way to grow plants indoors and will dramatically increase yields. Cheap Grow Lights highly recommends the use of an MH conversion lamp if you are using a HPS system for your indoor garden, our customers have reported significant yield increases with our conversion lamps!

What is a "horticultural" lamp (AgroMax, Sunmaster) and why do I need one.
A "horticultural" lamp, like the AgroMax or Sunmaster lamp, is a specially constructed lamp, designed specifically for horticultural purposes. Generally these lamps offer more usable light for plant growth than do standard HPS or MH lamps. Often times these lamps are higher in lumen output and have different spectral outputs geared toward different phases of plant growth. Independent studies have shown yields have been shown to be significantly increased with the use of these lamp types.

What about fluorescent lights? What is "T5"?
In the past, fluorescent lamps were typically not a good choice for lighting indoor gardens. Today, with improvements in technology and increases in light output, fluorescent lamps may be successfully used for growing indoors. The introduction of the T5 H.O. (high output) lamp has proven to be a lamp nearly rivaling (and in some ways surpassing) MH lamp technology. (NOTE, do not confuse T5 H.O. lamps with "standard" T5 lamps, as the latter are too low in light output and efficiency to be considered for indoor gardening). Generally, a T5HO fixture may be placed closer to an indoor garden because the heat produced by the lamp is spread throughout a longer tube than HID lamps. For example, a 250 watt MH lamp has a lumen output of 28,000 lumens, while a 4 lamp, 4' T5 HO fixture has a lumen output of 20,000 lumens; however the heat output of the T5 is spread evenly throughout nearly 16' of fluorescent tubes, while the MH lamp has the heat concentrated in a tube less than 1' long. Therefore, in typical use, the T5HO fixture could be placed within a few inches of the garden, while the MH fixture might have to be placed 1 or 2 feet way. The closer placement of the T5 fixture would allow for increased light intensity for this garden. Typically these fixtures are used mostly for smaller sized gardens or seed starting applications.

What wattage lighting system do I need?
The wattage of the lighting system needed for indoor gardening will be based on a couple of factors. 1) What are the lighting requirements of the plants in the garden? Are they plants that need high, medium or low light levels? 2) What is the size of the indoor garden? A garden needs "footcandles" not watts, so you will want to calculate how many "lumens per square foot" you will have in your garden. As a general rule, you will need at least 2,500 lumens of High Intensity Discharge (H.I.D.) light per square foot of garden. To get the square footage of your garden, simply measure the floor space where your garden will be and multiply the length by the width. So a 400 watt HPS (50,000 lumens) will light a 4' x 5' garden adequately. Remember, 2,500 lumens per square feet is the minimum amount of light you'll need. Typically the brighter the garden is, the faster the growth and the bigger the yield should be. Some growers suggest a 400 watt light for an area as little as 9 square feet (3' x 3').

Does my HPS or MH lamp need time to "warm-up"?
MH and HPS lamps are also know as High Intensity Discharge (HID) lamps. All HID lamps will require some amount of time for the gas in the arc tube to "warm up" and become fully bright. A MH lamp usually requires 5-10 minutes for full brightness while a HPS lamp may require less than 5 minutes. Additionally, in most MH or HPS systems, if the light is turned off, even momentarily, the lamp will "extinguish" and then need to fully "cool-down" before the arc will "re-strike" and light up again, this whole process may take up to 25 minutes.

Do I need special wiring for my indoor garden lighting?
Generally no special wiring is needed. All of the lights we sell are manufactured, tested and certified for safe use inside a home. The lights will operate with the use of a standard, household grounded power outlet. The only problems that may occur are when too many electrical appliances (lights, fans, etc) are powered through the same circuit. Most homes have 15 or 20 AMP maximum circuits. The AMP usage of your lighting system should be listed on the product information label on your ballast unit. Typically a 400 watt HPS or MH lamp uses about 4 AMPS while a 1000 watt unit will use 9.5 AMPS.

Do HPS and MH lamps explode?
It is recommended by all MH lamp manufacturers that the lights be turned off at least 15 minutes once per week to prevent "non-passive" (rupturing of the lamp) failure. This is a very easy recommendation to adhere to. HPS lamps are designed differently and can operate 24/7 indefinitely and are not subject to "non-passive" failures. Do not spray a hot lamp with water or cleaner. Always wait at least 30 minutes for the lamp to cool before you clean it with standard window cleaner.

How much electricity does my light use?
Each H.I.D. light uses the amount of wattage the light is plus an additional 15% for the ballast. So, a 400 watt HPS uses 400 watts for the lamp and another 15%, or 60 watts, for the ballast - for about 460 watts total, give or take. This is a general rule and the electrical consumption could be a little more or less than this.

How much does it cost to operate my indoor garden lighting system?
Below is a table based on operating the light only 12 hours a day at 8 cents per kilowatt hour. Check your electric bill for your electric rate. Wattage Estimated monthly cost 150 $4.97 250 $8.28 400 $13.25 1000 $33.12 To calculate your energy cost you will need to know 3 things: A: Your cost of energy (usually identified as "KWH" charge on your electric bill) B: The total watts of your lighting system C: The total operating hours ("ON" time) of your lighting system per month. Formula = A * B/1000 * C = Total Energy Cost per month So for the above table: A = $.08 , B = 460, C = 360 hours (12 per day * 30 days) = Total charge of $13.25

120 volt or 240 volt, am I saving electricity?
This is the biggest myth in the indoor gardening world. There is absolutely no energy savings by using 240 volts instead of 120 volts. Remember back to your high school science class, you learned something called "Ohm's Law", that states P = I * E. In this equation, P = Power (watts), I = current (Amps), E = Voltage. To demonstrate, a typical 400 watt HPS lighting system is rated at 3.8 Amps at 120 volts or 1.9 Amps at 240 volts. (This information can be found on the electrical label found on your lighting system's ballast unit). Therefore the energy used for the 400w HPS light for the different voltages is: 120v = 3.8 Amps x 120 volts = 456 watts 240v = 1.9 Amps x 240 volts = 456 watts While there is no energy savings associated with using 240 volts, there is an advantage for indoor gardens that are utilizing many lights. Basically you can operate twice the amount of lighting systems on a 240 volt circuit than you can on a 120 volt circuit.

How long do MH and HPS lamps last? When should I replace my lamps?
Most lamps sold have a "rated life" that is stated on the carton or the literature. Rated life refers to the point at which 50% of the lamps will be "burned out" and 50% of the lamps will still operate. Most HPS lamps have a rated life of 24,000 hours. Most MH lamps have a rated life of 10,000-20,000 hours. Because all MH and HPS lamps will slowly "depreciate" (decrease in light output) over time, most indoor gardeners replace the lamp long before it "burns" out. Many indoor gardeners will replace a HPS lamp after 1 year and an MH lamp after 9 months of use. Because your indoor garden yields are so closely tied to light output, a 10% decrease in light to the garden may result in a 10% decrease in yields. An HPS lamp will lose approximately 20% of its light before it "burns out" while an MH lamp will lose up to 50% of its light output before it "burns out".

Why is ordering from Cheap Grow Lights so great?
Ask any plant and they will tell you that they prefer lighting systems from Cheap Grow Lights. Not only are the lighting systems top quality, but the gardeners who choose Cheap Grow Lights receive their lights quickly in discreetly packaged shipments and save a TON of money over retail and other websites. Gardeners can choose to order over the internet, call in their orders or pay by money order/check. Cheap Grow Lights will meet or beat any advertised price on comparable lighting systems, just let them know if you think you've found a better deal anywhere (not likely).