Get Information About Your Indoor/ Greenhouse Garden Lighting Needs!!

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Get Information About Your Indoor/ Greenhouse Garden Lighting Needs!!

Q: What are the different types of plant Lighting? High Intensity Discharge (HID) Magnetic and Electronic Metal Halide (MH) & High Pressure Sodium (HPS), Fluorescents with blue, red, or mixed spectrum bulbs, or the newest development in horticultural lighting - LEDs (Light Emitting Diode).

Q: What are conversion lamps/bulbs?

Q: What wattage light system should I get for my grow space?

Q: Hanging Height - How high should I hang my grow light?

Q: How many amps does my light system draw?

Q: How much does the electricity cost to operate my light system?

Lighting Glossary

Q What are the different types of plant lighting?

A: Helpful information for choosing the right grow light type: Both the professional and hobbyists communities generally accept that plants require a biased ratio of “blue” light during vegetative growth for enhanced performance. While the implementation of a “warm red” light during fruiting is regarded as the standard. Green chloroplast cells within the plants preferentially utilize the blue color spectrum (4200k to 6700k) during vegetative growth over those that fall within the red to orange spectrum. As a result of this preferred association many studies have been conducted that indicate a strong morphological response within the plant that is expressed by the elongation of cells. This response equates to more vigorous and robust juvenile growth. The “infrastructure” derived as a result of an increase in blue light exposure, will allow the plant to effectively manage a large fruit load during harvest. Similarly, “warm” light simulates autumn and when coupled with a decrease in the duration of the exposure will trigger a strong fruiting response in plants and encourage large yields, short internodal spacing and dense flower sets.

Home gardeners and commercial growers can now grow 12 months a year with high intensity Grow Light Systems. Metal halide and high pressure sodium Grow Lights are the most efficient and productive lighting system available from seedling to maturity. Fluorescents or LEDs are an extremely energy efficient alternative to HIDs. An important concept to remember as you read the information below is that in general a High Pressure Sodium (HPS) system may only use HPS bulbs and Metal Halide (MH) systems may only use MH bulbs. Alternatives to this general rule are explained below under the Conversion Lamps section and the Switchable and Electronic Systems section. Below you will find more information relating to the categories in Blue.

Metal Halide (MH) HID Light: MH HID Grow Lights featuring metal halide HID lamps provide high lumens and primarily blue/violet spectral energy for seedling and vegetative growth. Metal halide lamps are available from 2600 Degrees Kelvin (increased red spectrum) for enhanced flowering to 7200 Degrees Kelvin (higher blue/violet spectrum) for enhanced vegetative growth. Continue on for more information on each of these lamps to determine which is the best system for you.

High Pressure Sodium (HPS) HID Light: HPS HID Grow Light systems featuring high pressure sodium (HPS) HID lamps provide high lumens and primarily red spectral energy for growth during a plants budding, flowering and fruiting stages. HPS lamps are available from 2000 Degrees Kelvin (red spectrum) to 3000 Degrees Kelvin (enhanced blue spectrum). Continue on for more information on HPS lamps to determine the best grow light system for you.

Electronic HID Systems: Electronic HID Grow Light systems allow the use of metal halide during the vegetative growth stage and HPS during the budding and flowering stages by simply changing the bulb. No special conversion bulb is needed. They also offer a number of other advantages over the Magnetic: Lightweight, Extremely efficient, 99.9% power factor, Soft starting, increases lamp life & reduces lumen depreciation, and Silent operation. These systems eliminate the need for conversion lamps or multiple light systems.

Switchable HID Systems: Switchable Magnetic HID Grow Light systems allow the use of metal halide during the vegetative growth stage and HPS during the budding and flowering stages with the simple flip of a switch. These systems are slightly more expensive than single wattage systems and are available in many wattages but they eliminate the need for conversion lamps or multiple light systems.

Conversion HID Lamps: Conversion lamps are available in limited wattages for either metal halide or HPS grow light systems. Metal halide conversion lamps operate on an HPS ballast during the vegetative growth stages and HPS conversion lamps operate on metal halide ballasts systems during the budding and flowering growth stages. Conversion lamps may also be alternated in multiple fixture, commercial growing environments to achieve a balanced spectral output during all growing stages. Conversion lamps are available as a separate purchase and are not included with a grow light system.

Fluorescent Grow Lights:
Fluorescent grow lights come in compact, 2', 3' and 4' fixtures. They are energy efficient with silent and cool operation. All fluorescent systems will accomodate both blue spectrum and/or red spectrum lamps. Blue (cool) spectrum fluorescent lamps are used for seedlings, clones, and the vegetative growth stage. Red (warm) fluorescent lamps promote fruiting and flowering. A mix of red and blue fluorescent lamps can be used in the 2-8 lamp fixtures to produce a mixed color spectrum for full term growth / mixed plant stages.

LED Grow Lights: Leds (light-emitting diode) are the newest development in hortilcultural lighting. They run extremely efficient, silent, and cool. Leds eliminate the need for expensive heat exhaust equipment.

A: HID Conversion lamps (bulbs) are specially made bulbs that work with the opposite type of HID grow light (MH conversion lamps work with HPS lights and HPS conversion lamps work with MH lights). Note that most electronic/digital and all switchable grow lights power both MH & HPS bulbs (no special conversion bulb needed). Conversion lamps may also be alternated in multiple fixture commercial growing environments to achieve a balanced spectral output during all growing stages. Conversion lamps are available as a separate purchase and may be substituted for the standard lamp in our light packages for a modest price increase.

MH Conversion Lamps

250 watt metal halide conversion lamps operate on 250 watt high pressure sodium grow lights.
400 watt metal halide conversion lamps operate on 400 watt high pressure sodium grow lights.
600 watt metal halide conversion lamps operate on 600 watt high pressure sodium grow lights.
1000 watt metal halide conversion lamps operate on 1000 watt high pressure sodium grow lights.

HPS Conversion Lamps

150 watt high pressure sodium conversion lamps operate on 175 watt metal halide grow lights.
220 watt high pressure sodium conversion lamps operate on 250 watt metal halide grow lights.
360 watt high pressure sodium conversion lamps operate on 400 watt metal halide grow lights.
940 watt high pressure sodium conversion lamps operate on 1000 watt metal halide grow lights.

Q: What wattage light system should I get for my space?

A: Most indoor gardeners use about 25 watts per square foot of garden space. You may need less if your light is used to supplement natural sunlight, or if you are growing a plant that does not require as much light (i.e. lettuce). However, many gardeners prefer to double or even triple the recommended wattage to achieve faster growth rates. There is really no such thing as too much light, but using a big light in a small space will sometimes result in high temperatures that are difficult to control.

H.I.D. & Fluorescent Recommended Light Coverage

HID Grow Light Wattage/Type	Primary Light (no other lighting or natural sunlight)	Secondary Light (used with other lights or natural sunlight)
100 Watt MH or HPS	1.5’ X 1.5’	2’ x 2’
150/175 Watt MH or HPS	2’ x 2’	3’ x 3’
250 Watt MH or HPS	3’ x 3’	4.5’ x 4.5’
400 Watt MH or HPS	4’ x 4’	6’ x 6’
600 Watt MH or HPS	5’ x 5’	7.5’ x 7.5’
1000 Watt MH or HPS	6’ – 6.5’ x 6’ – 6.5’	9’ x 9’

T5 Fluorescent Grow Light	Primary or Stronger Light	Secondary or Lower Light
2 Tube Fixture (24” tubes)	2 Square Feet (2’ x 1’)	3.75 Square Feet (2.5’ x 1.5’)
4 Tube Fixture (24” tubes)	4 Square Feet (2’ x 2’)	7.5 Square Feet (2.5’ x 3’)
8 Tube Fixture (24” tubes)	8 Square Feet (2’ x 4’)	12.5 Square Feet (2.5’ x 5’)
2 Tube Fixture (48” tubes)	6 Square Feet (4’ x 1.5’)	9 Square Feet (4.5’ x 2’)
4 Tube Fixture (48” tubes)	12 Square Feet (4’ x 3’)	18 Square Feet (4.5’ x 4’)
8 Tube Fixture (48” tubes)	24 Square Feet (4’ x 6’)	36 Square Feet (4.5’ x 8’)

The secret to providing the most efficient lighting is considering color, intensity, and duration. Plants need periods of darkness and will grow and produce best when the day length and color imitate the season the plant normally grows well in. An example of this is using red color spectrum and shorter 12 hour days for fall flowering/fruiting plants VS. blue color spectrum and longer 18 hour days for plant starts and superior growth. Also, using a light timer to automate your lighting adds convenience and encourages productive growth with consistent hours of light.

Q: How high should I hang my grow lights?

A: H.I.D. lamps should be hung between 12" - 48" from the top of your plants, depending on the light wattage. Make sure to check for excessive heat at the top of your plants by placing your hand (palm down) over your plants. If the top of your hand is hot, you need to move your lamp further away. If the light source is too close to your plants you can burn them. Remember that as your plants grow you will need to adjust the height of your lamp. Also, keep in mind that the latest air-cooled reflectors, like the XtraSun 6" Air Coolable Reflector by HydroFarm, allow you to place higher wattage bulbs closer to plants than was possible in the past.

Fluorescent and L.E.D. Grow Lights can be placed much closer to plants than an H.I.D. fixture because they produce very little heat. Place fluorescent or LED grow lights 2" - 4" from plant tops, or as close as you can without excluding the outside perimeter of your garden.

Note: No matter what type of lighting you choose, when you raise the light up & away from your plants the light levels at your plant will be significantly reduced. For high-light loving plants, keep your lights as close as possible without burning them. Alternatively, you can move the light further away for low-light plants.

Q: How many amps does my light system draw?

A: To figure out how many amps (amperes) your ballast or grow light draws, calculate the Watts divided by Volts. For example, a 1000 watt ballast on a 120 volt circuit (standard household plugin): 1000 / 120 = 8.33 amps. A 1000 watt ballast on a 240 volt circuit: 1000 / 240 = 4.17 amps.

Q: What does the electricity cost to operate my grow light?

A: To get an estimate on how much your electricity bill will increase due to your grow light, follow the following equation:

Number of days light is 'on' each month X number of hours the light is 'on' each day X wattage of light. Then divide the total by 1000 to get your kilowatt hours. You can then multiply the kilowatt hours by the kilowatt rate on your electric bill. For example, 30 days 'on' time x 12 hours per day x 400 watts = 144,000. 144,000 / 1000 = 144 kilowatt hours. 144 kilowatt hours x an assumed $0.05 kilowatt rate = $7.20 estimated increase to your electric bill.

Ampere (Amp): An ampere represents the amount of electrons passing a given point per unit time. Approximately 6.242 × 1018 electrons passing a given point each second constitutes one ampere.

Arc: The discharge of electricity between two electrodes.

Ballast: An auxiliary piece of equipment designed to start and to properly control the flow of power to gas discharge light sources such as fluorescent and high intensity discharge lamps. In metal halide systems, it is composed of the transformer, capacitor and connecting wiring; sodium systems require an ignitor in addition to the transformer and capacitor.

Bulb: The glass outer envelope that houses the arc tube.

Capacitor: An electronic device capable of holding a strong electrical charge. The charge is then released in a “one shot” fashion and as a result can pose a serious health risk to anyone unfamiliar with its operation.

Cold Start Time: The time it takes for a cold HID lamp to achieve a lumen output that is indicative of its functional range.

Diffuse Reflection: Type of reflection exhibited by a ray of light whose angle of reflection is not equal to the angle of incidence as a result of an irregular incident surface. The texture of the incident surface may be hard to discern as many high performance diffusion films are composed of nano-fibers and their structure is not perceptible to the naked eye.

Kelvin Temperature Rating: A common standard used to describe the color of light a lamp emits as perceived by the human eye. The temperature rating is derived from the light that is emitted from a “Theoretical Black Body Radiator” that starts a -273 C or absolute zero and is raised incrementally until it begins to emit light. As the temperature of the TBB is increased the color of light that is perceived by the human eye changes.

Conversion Bulb: A HID bulb designed to be used on either an HPS or MH regardless of its primary spectral output. Examples include HPS conversion bulbs that function on a MH system.

Electrodes: Filaments engineered to sustain an electrical arc in the void between them.

Fluorescent Lamp: A lamp that produces light by supplying current to electrodes contained within low-pressure argon filled tube. These electrodes excite a small amount of mercury amalgam contained with the aforementioned envelope and a portion of the mercury changes phase into a gas. As the charged atoms, electrons and gaseous mercury collide within the space the charged mercury atoms become excited and release photons in the Ultraviolet spectrum these UV photons excite the phosphor coating located on the inside of the tube and photons within the visible light spectrum are produced as a result.

Footcandle: A unit of illuminance that is equal to the light emitted by one candle at a distance of one foot.

Frequency: The number of waves or cycles of electromagnetic radiation per second, usually measured in Hertz (Hz).

High-Intensity Discharge (Hid) Lamp: A general term for mercury, metal halide and high-pressure sodium lamps. HID lamps contain compact arc tubes which enclose various gases and metal salts operating at relatively high pressures and temperatures.

High-Pressure Sodium Lamp: High-pressure sodium lamps operate by igniting sodium, mercury and xenon gases within a sealed ceramic arc tube. Sodium lamps emit light energy in the yellow/red/orange regions of the spectrum; the red spectrum stimulates flowering and fruit production. Many indoor gardeners switch to sodium lamps when it is time to induce flowering or fruiting of their plants.

Hood: A generic term used to describe the lamp housing of an HID bulb.

Hot Spot: The area immediately under an HID lamp where the light intensity is strongest. Hot spots cause uneven growth, but can be remedied by using light movers.

Hot Start Time: The length of time required to bring an HID lamp to 90% light output after a short power interruption.

Ignitor: A component of the ballast necessary for the starting of the bulb in sodium systems.

Incandescent Lamp: A light source which generates light utilizing a thin filament wire (usually of tungsten) heated to white heat by an electric current passing through it. Incandescent lamps are the most familiar type of light source, with countless application in homes, stores and other commercial settings. Light is produced by passing electric current through a thin wire filament, usually a tungsten. Incandescent lamps are totally ineffective as grow lights; they have very limited spectrum, are very inefficient in their conversion of electrical power to lumens of light output (lumen-to-watt ratio). They also put off far too much heat per watt to use in horticulture, even if the abovementioned problems did not exist.

Intensity: A term referring to the magnitude of light energy per unit; light intensity diminishes evenly as you get further from the source.

Kelvin Temperature (K): The unit of measurement to express the color (spectrum) of light emitted by a lamp; the absolute temperature of a blackbody radiator having a chromaticity equal to that of the light source (see correlated color temperature). A standard clear metal halide HID lamp has an average Kelvin temperature rating of 4,000K.

Lamp Life: A measure of lamp performance, as measured in median hours of burning time under ANSI test conditions.

Light: Radiant energy that can be sensed or seen by the human eye. The term generally applied to the visible energy from a source. Light is usually measured in lumens or candlepower. When light strikes a surface, it is either absorbed, reflected or transmitted. Visible light is measured in lumens.

Lumen: A measurement of light output; refers to the amount of light emitted by one candle that falls on one square foot of surface located at a distance of one foot from the candle.

Lux: Is the standardized metric unit of luminous emittance and is useful when discussing the functional intensity of a lamp as perceived by the human eye.

Metal Halide Lamp: Nearly identical in their configuration, MH lamps differ from HPS addition of rare earth metal salts to the standard mercury vapor lamp. This design change leads to improved luminous efficacy and superior light color is obtained. However not unlike other HID lamps metal halide lamps operate under high pressure and temperature, and require special fixtures to operate safely. Originally created in the late 1960's for industrial use, metal halide lamps are now available in numerous sizes and configurations some specifically suited for use in indoor gardening.

Mercury Vapor Lamps: The oldest member of the HID family, mercury vapor lamps work by arcing electricity through mercury vapor. While more efficient than incandescent, halogen and fluorescent lamps, mercury vapor lamps have the least efficient lumen-to-watt ratio of the entire HID family. This, combined with an improper color spectrum for horticultural applications, makes mercury vapor lamps a poor choice for a grow light.

PAR (Photosynthetically Active Radiation): A unit of measurement used to describe the quality of light a given lamp emits as seen by the plant. PAR meters and their subsequent generated values indicate the quantity of light in the 350-750 nm range as this is what is regarded as useful for vegetative propagation. All other frequencies are exempted from the value.

Parabolic Reflector: A reflector fashioned in the shape of a parabola. Seen by many as an exceptionally efficient design however it has challenges when applied to the traditional square or rectangular footprint of most indoor gardens.

Phototropism: The physiological response of a plant to an external light stimulus.

Quantum Meter: An instrument designed to measure instantaneous Photosynthetic Photon Flux (PPF) in μmol m-2 s-1. This measurement is considered by many to be the only true method for determining the value of plant available light produced by a lamp.

Reflector: A term sometimes used to refer to the hood unit of an HID lighting system.

Reflectivity: The measure of the reflective quality of a surface; the relative ability of a given surface to reflect light away from it without absorbing, diffusing or otherwise compromising the light’s quality, intensity and spectrum.

Socket: The threaded, wired receptacle that a bulb screws into.

Sodium Lamp (High-Pressure Sodium Lamp): High-pressure sodium lamps operate by igniting sodium, mercury and xenon gases within a sealed ceramic arc tube. Sodium lamps emit light energy in the yellow/red/orange regions of the spectrum; the red spectrum stimulates flowering and fruit production. Many indoor gardeners switch to sodium lamps when it is time to induce flowering or fruiting of their plants.

Specular Reflection: The reflection of a ray of light equal to the angle of incidence. This type of reflection is sometimes considered inferior for agricultural propagation to diffuse reflection due to the inherent hot spots created by the prior.

Transformer: The component in the ballast that transforms electric current from one voltage to another.

U (For Universal): An industry code indicating that the bulb can be operated in any position: horizontal, vertical (base up) or any other.

Ultraviolet (Uv) Light: Harmful to the human eye, UV light can be used for a myriad of other tasks including sterilization and inducing high level photo stress to a plant during the late stages of bloom to encourage an amplified fruiting or blooming response.

Watt (W): A unit used to measure electric power. One watt equals one joule/second.