For reflector measurements, glass sizes, air cooled fittings options, built in socket & lamp cord availability, glass retention, reflectivity and lamp positioning please see the Sun System Reflector Quick Reference.
Lamp cord plugs by manufacturer
Most manufacturers use proprietary socket cord ends and corresponding ballast plugs:
C.A.P. & COMMON (orange)
Frequently Asked Questions & Answers
Why use a garden light for indoor gardening?
Grow lights are usually the most expensive item in the indoor garden, so it's important to choose the
right one for your requirements. You should measure the square footage of your garden area, and consider the
plants that will be grown. Different plants have different light requirements. Normally, the taller the
plant, the more light required in order to reach the lower sections. Plants that flower or fruit typically
require more light than those which do not, e.g. herbs.
Fluorescents are fine for starting seeds or cuttings, but are not powerful enough to light an area more
than 8" - 10" below the bulb. Although more efficient than incandescents, they are still much less efficient
than HID light systems. HID (High Intensity Discharge) light systems have revolutionized indoor gardening in
the last two decades. They are the most energy efficient grow lights available, so they produce much more
light for the amount of power consumed. Horticulture Source offers garden lights in MH and HPS. Metal Halide
(MH) bulbs emit a light spectrum which appears blue-white to the human eye. This color spectrum is more
conducive for vegetative growth, or starting seeds & clones. High Pressure Sodium (HPS) bulbs emit a spectrum
which is more concentrated in red/orange light. This color is ideal for the fruiting and flowering stage of a
plant's development. It is a good multi-purpose light as well. Larger wattage systems will cover larger
growing areas, and since these bulbs produce greater light intensity they are superior for growing taller
plants such as tomatoes.
Most gardeners use at least 25 watts per square foot of garden space. You may need less if your garden
light is used to supplement natural sunlight, or if you are growing a plant that does not require as much
light, e.g. 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. Keep in mind that
plants need periods of darkness too. Most indoor gardeners use supplemental lighting from 10 - 16 hours per
Keep an HID bulb about 30" - 36" above the top of your plants. (This is an average distance...lower
wattage bulbs may be placed closer, while higher wattage bulbs may need to be placed further away). Higher
wattage bulbs provide more intense light for large growing areas. Lower wattage systems are used for smaller
garden areas. Note: the height of the reflector/fixture above the plants will also affect coverage area.
Average coverage area by wattage:
150 watts — 2' x 2'
175 watts — 2' x 2'
250 watts — 3' x 3'
400 watts — 4' x 4'
600 watts — 6.5' x 6.5'
1000 watts — 8' x 8'
W = AV [Watts equals Amperage (Amps) times Voltage]
On average a garden light will increase your electricity cost from $5 to $8 per month (the exact amount
depends on the size of the system and the number of hours operated). However, since these grow lights are so
energy efficient, you are getting huge amounts of light (and growing power) for your money! Make sure your
grow room's power circuit can handle the power draw. For safety reasons, do not exceed 75% of the rated
ability of the fuse (for example: use no more than 15 amps on a 20-amp circuit). To calculate your cost,
multiply the bulb wattage X hours of operation and divide by 1000. This figure is the number of kilowatt
hours of electricity consumed. (Example: a 400 watt bulb running for 18 hours will use 7.2 kilowatt hours).
Check your power bill for the cost of each kilowatt hour.
All fertilizers, liquid and granular nutrients are labeled with the percentage by weight of major
nutrients: N-P-K or Nitrogen — Phosphorus — Potassium, e.g.
6-5-8 means 6% Nitrogen, 5% Phosphorus, and 8% Potassium by weight.
Secondary Nutrients — Ca, Mg, S
Essential Elements — C, H, O
Macronutrients — C, H, O + N, P, K + Ca, Mg, S
Minor Elements — Fe, B, Mn, Cu, Cl, Mo, Zn
Concentration measured in ppm (parts per million) utilizing a TDS meter or instrument.
When mixing liquid nutrients use distilled water or water from a reverse osmosis (RO) filtration system.
This can be done in a reservoir. Water can get stagnant, to avoid this utilize a swirl pump as well as an
EC, TDS, PPM, MilliSiemens (ms), MicroSiemens (µs or sometimes 'us')
To measure how strong a nutrient solution is
the amount of salts in the liquid or Total Dissolved Solids (TDS)
is measured in Parts Per Million (ppm) by
Electrical Conductivity (EC)
MilliSiemen (ms) or MicroSiemens (µS) and converting to ppm. The more salt in the water the higher the conductivity the higher the ppm.
Distilled water is not conductive and would have 0ppm.
Parts Per Million (ppm) = MicroSiemens (µS)/1.56
MicroSiemens (µS) = 1.56 * Parts Per Million (ppm)
Total Dissolved Solids (TDS) in ppm = (Electrical Conductivity (EC) * 1000)/2
1 MilliSiemen (ms) = 1000 MicroSiemens (µS) that is (1.0 ms/cm = 1000.0 µs/cm)
pH is a measure at how acidic or alkaline your nutrient solution is. The pH scale
goes from 0-14 with 0 up to 7 being acid, 7 neutral, and over 7 to 14 alkaline. Most plants
prefer the pH to be in the 6-7 range. Beyond this point some nutrients become less available
for your plants' absorption.
The measurement of the acidity of a solution, in terms of activity of hydrogen ions (H+) is measured
utilizing an electronic pH meter / instrument, chemical pH test kit or a pH test strip. Most common
ornamental houseplants prefer a pH around 6.5. A pH from 5.5 to 7.5 is the range most vegetables
Crop production with mineral nutrient solutions instead of soil containing silt and clay. Terrestrial plants may be grown with their roots in the mineral nutrient solution only or in an inert medium, such as sand, gravel, clay pellets, or rockwool. A variety of techniques exist.
With a pair of clean and sharp pruning sheers cut at about a 45 degree angle below at least two densely
placed nodes. Using an angled cut maximizes the surface area of the cut. Clip off the bottom two nodes
smooth against the main stem. Clip off all lower foliage leaving only the new top growth. Dip the 45 degree
cut and sheered off nodes into rooting compound for the 10 - 30 seconds (depending on the thickness and
woodiness of cutting). Place dipped end into desired medium. Maintain moisture, high humidity levels (over 60%) and
about 80 degrees Fahrenheit (80° F). Spray the remaining foliage with anti wilt spray. Maintain low
levels of nutrients until roots form (e.g. < 300 ppm & NPK 8-5-8). Aeroponic rooters can produce root
growth within three days. Utilize 24 hours of fluorescent or low wattage metal halide lighting.
Carbon dioxide also known as CO2 or CO2 (sometimes people write CO2). Plants breathe
in carbon dioxide while making food via photosynthesis. As such elevated levels of CO2 should
only be present during light hours. Blue burning flames, our exhaled breath, and the digestion of sugar by
yeast, etc. creates CO2. Where a commercial CO2 generator is used (burning propane), the area should be vented and
fresh air be periodically blown in, e.g. generate CO2 with intake and exhaust fans off and
maintain CO2 levels for 45 minutes, then stop generating CO2, vent CO2
outside and draw in fresh air, and repeat utilizing a controller. This ventilation will also help maintain
temperature and humidity levels.
At very high levels, 30,000 ppm and above, CO2 can cause asphyxiation as it replaces oxygen in
Different plants have different requirements. Some plants bloom at night for example while some
orchids bloom with 16 hours of light. Generally however switching to only 12 hours of light per day incorporating HPS (High Pressure Sodium) lighting will bloom most plants.
Increase amount of nutrients, phosphorus and potassium levels, e.g. NPK 9-19-13 at 1200 ppm. Increase
CO2 levels during light on time, e.g. 5000 ppm.
HID lighting stands for High Intensity Discharge, which is a special type of lighting that is much more intense (brighter) than other type of lighting available. An HID lighting system consists of a ballast, reflector, socket and lamp (light bulb). The ballast acts like the engine, converting and driving energy to illuminate the lamp. HID lighting options include High Pressure Sodium (HPS), Metal Halide (MH), Mercury Vapor and Low Pressure Sodium. The two typically used for plant growth are HPS and MH systems.
What are Color Rendering Index (CRI), Color Temperature (K) and Lumen?
Color Rendering Index is a subjective measurement of how well a lamp source renders colors. A measurement of the degree of color-shift an object undergoes when illuminated by a light source when compared to a reference source of comparable color temperature. Incandescent light is assumed to have a CRI of around 100 so it will render all colors correctly. MH only has a CRI of about 70, so only 70% of colors will be rendered correctly. HPS has a CRI of 22.
Color Temperature is not how hot the lamp is. Color temperature is the relative whiteness of a piece of tungsten steel heated to that temperature in degrees Kelvin. HPS has a warm (red) color temperature of around 2700K as compared to MH at 4200K, which has a cool (blue) color temperature.
What is important to remember about these two terms is that CRI readings, of two sources, can only be compared if their color temperature is equal. You cannot compare the CRI of HPS (CRI=22) vs. Metal Halide (CRI=70) because the color temperatures are different (2200K vs. 4500K)
Lumen is a measurement of light output. It 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. Traditionally, lumens have been the benchmark of a lamps ability to grow plants; meaning the brighter the lamp the better the plant. However, studies have shown that a broader color spectrum lamp will perform much better than a lamp with high lumen output, especially when it comes to plant growth.
What is the difference between MH and HPS with regards to plant growth?
MH lamps provide more of the blue/green spectrum, which is ideal for leafy crops, and/or plants that are in a vegetative (actively growing) stage. MH lamps provide a more natural appearance in color and are typically the choice for plants that have little to no natural light available. HPS lamps provide more yellow/orange/red spectrum, which is ideal for most plants that are actively fruiting and flowering. In addition, HPS lighting is the choice for growers looking to supplement natural sunlight. Ideally, the horticulturalist will use MH to grow their plants and HPS to fruit and flower their plants.
What is the difference between HID and Fluorescent lighting with regards to plant growth?
Traditionally, fluorescent lighting was used for seedlings, cuttings and plants with low light-level requirements and HID was used for established plants and plants with higher light-level requirements. Advances in fluorescent lighting technology, however, have provided more options for horticulturists. T5 fluorescent lighting is the latest in plant growth lighting. T5’s high-light output combined with its low heat and energy consumption makes it an ideal light source to grow a broader array of plants.
What are the benefits of using T5 fluorescent lighting for plant growth?
T5 lamps provide the ideal spectrum for plant growth. Photosynthesis rates peak at 435 nm and 680 nm. A 6500K T5 lamp has a spectral distribution with relative intensity peaks at 435 nm and 615 nm. This equates to very little wasted light energy in terms of plant growth. T5 lamps promote incredible health and vigor of seedlings and cuttings. Root development is superior relative to other lighting sources. While T5 lighting is excellent for starting seeds and cuttings, it’s also able to produce enough light for full term growth. Because of their minimal heat output, T5 lamps can be placed 6” -8” above the plant canopy which maximizes photosynthetic response. Unlike conventional fluorescents, plants grown under T5 lamps do not have to be rotated to the center of the lamp. T5’s slim diameter enables better photo-optic control of the emitted light, increasing efficiency in the form of even light distribution.
Aquariums & Reef Tanks: What are the benefits of T5 lighting?
A critical parameter of good coral growth and survival, especially hard corals, is light. With the advent of 15’s (which describes the small diameter of the tube - 5/8 — and does not indicate the lumen out- put), and correct phosphor blends, it is possible to produce a fluorescent tube which can emit I 0% more light than the equivalent wattage from a metal halide bulb. This is achieved with a 40% reduction in running cost and without the radiant heat problems associated with metal halide lighting. The tubes are significantly less expensive than metal halide bulbs with increased longevity up to I 5,000 hours.
The T5 tube is only half the story
The narrow diameter of the standard linear T5 tube, allows Sunlight Supply® to manufacture a highly efficient reflector. The reflector’s gull wing shape, allows light from the back of the tube to be utilized; not reflected back through the tube where to be lost. This is only possible due to the T5’s narrow diameter and linear format, which reflects light in a clear path away from the tube.
SUITABLE FOR SALT WATER AND FRESH WATER.
Recommended D-D marine tube is a 60/40 white/blue blend. Specifically developed to grow SPS corals down to 800cm. Suitable for salt water, reef and fresh water fish only aquariums. Ideally suited as a standalone, or in a 2:1 or 3:1 fashion, with blue or actinic supplementary lamps.
This is the ultimate marine lamp.
T5 Diameter High Output Fluorescent Lamp
60% actinic 40% white spectrum
Color temperature approx I 5,000K crisp color as stand-alone lamp
A 6000 Kelvin tube with a 5-point spectrum, recreating sunlight. Suitable for salt water, fresh water, and reef planted or fish only aquariums. Full spectrum use for growth of SPS and when used in a 1:1 ratio with either the Actinic or Aquablue+ supplementary lamps.
A pure actinic tube complete with all the power of the “T5” illumination. Will fluoresce corals and when blended with the HQI or Midday 6000K, brings out the maximum color. Spikes at 420 nanometers for ultimate fluorescence of capable coral. The ONLY T5 HO true actinic available on the US market.
A mixture of 40% Actinic and 60% Blue makes even the drabbest corals stand. Great when used with
1 OK or 6500K metal halide lamps to encourage bluing in SPS. 450nm peak is similar to Radium Blue
metal halide lamps. Other preferred ratios include 1 :1 with Midday Lamps, or 2:1 :1 Midday/AquaBlue
+/Actinic for best blend of bluing and fluorescence.
T5 Diameter High Output Lamp
Blue spectrum peaks at 450 nm
Supplementation lamp encourages bluing in SPS coral, minor fluorescing.
What are the major differences between HID ballasts and electronic ballasts?
Frequency output to the lamp and energy conversion from electricity to usable light are the biggest differences between HID ballasts and electronic ballasts. HID ballasts produce a frequency of 60 Hz. Electronic ballasts vary from manufacturer to manufacturer, but the frequency produced can be 400x that of an HID ballast. HID ballasts produce more heat than electronic ballasts, thus making electronic ballasts more energy efficient. You will not, however, save money on your electric bill by using electronic ballasts. HID lighting has been available for 60+ years, while electronic ballast (especially 400 watt and higher) is a relatively new technology.
Electronic ballasts are more efficient at converting electricity into usable light. Since your power bill is based on kilowatt-hours and not efficiency, a 1000 watt electronic ballast will cost you about the same as a 1000 watt HID ballast to operate.
An average lighting system will increase your electricity cost about $8 to $20 per month. The exact amount depends on the wattage of the system and the number of hours operated. To calculate your cost, multiply the bulb wattage X the number of hours of operation and divide by 1000. This figure is the number of kilowatt-hours of electricity used. (Example: a 400 watt lamp running for 18 hours will use 7.2 kilowatt-hours). Check your power bill for the cost of each kilowatt-hour. Then multiply the number of kilowatt-hours used by the cost of a kilowatt-hour (K/hr) to figure the cost to run your light for that many hours.
Do I need special wiring in my house for my lighting system?
Lighting systems are available in a variety of voltages. The standard used by most gardeners is 120 volts / 60 Hz which plugs into a standard wall outlet. Other voltages may require special circuits and receptacles. Always contact a licensed electrician if the light you purchased has special voltage requirements and never exceed more than 75% of the rated ability of the fuse/breaker. (For example: use no more than 15 amps on a 20-amp circuit.)
Will I save on my electric bill if I run my system with 240 volts?
No. Electric companies base your electrical bill on Wattage, not Voltage or Current. While ballasts wired for 240 volt will draw less current and run a little cooler than one wired for 120 volt, it will not save you money on your electric bill.
Most lamp manufacturers rate their lamps by “Average Life Hours” and usually claim 10,000 to 24,000 hours. These ratings are based on when the lamp will completely fail to come on. They do not factor in loss of intensity or loss of color. HID lamps lose intensity and color through normal use. This is OK if you are lighting a warehouse, but when it comes to plant growth, these losses can mean wasted electricity and poor plant performance. Serious horticulturalists recommend that you replace your lamps after 6000 hours of use. This equates to using your light 16 hours a day for one year.
This depends on the type of plants and whether you have natural sunlight available to your garden. As a general rule, when you are in a vegetative stage of plant growth and you have no natural sunlight, run your lights 14-18 hours a day. If you have natural sunlight, it will vary because the sunlight may or may not be direct. It will take a little experimenting to find the best length of time to run your lights. If you are actively fruiting and flowering, the rule is to run your lights 12 hours a day if you have no natural light.
How high do I need to hang my lights above my plants?
The higher the wattage the further away you want the light to be from your plants due to the amount of heat. HID lighting will be further away than a fluorescent fixture because of this. When mounting your lighting fixture take into account the type of plant and how tall the plant will grow. You want to keep the light as close as you can, but not so close to burn the plant. A simple rule is “if it is comfortable for the back of your hand, it will be a safe distance for your plants”. Doing a little research on the type of plant and where it comes from will help in determining how much (or little) light your plants like. With fast growing plants, you may need to check the hanging height on a regular basis as plants that get too close to the lamp will be severely burned.
The size of the garden area will determine the wattage you need. If we assume that the plants will get no sunlight, a 1000 watt light will cover about 7 x 7 feet of growing area. A 600 watt will cover 6 x 6 feet, a 400 watt will cover 4 x 4 feet, and a 250 watt will cover 3 x 3 feet. These sized areas would be considered the “Primary Growing” areas. These lights will light-up larger areas, but plants placed outside of the Primary Growing area, will stretch and bend toward the light; a phenomenon called phototropism. Keep these areas of coverage in mind when using multiple fixtures. The best results occur when the areas of coverage overlap.
Why do I need glass to get the UI Listing on a Metal Halide light?
The inner arc tube of a Metal Halide lamp contains mercury. Underwriters Laboratory has stated that for a Metal Halide fixture to maintain its UL Listing, that an additional tempered safety lens is required in the event that the arc-tube and outer glass fail. This will prevent the spread of Mercury.
Can I run a 1000 watt bulb in my 400 watt lighting system?
No! The internal components of the ballast are designed to send the correct voltage and current for the rated lamp. Mixing lamps and ballasts will result in premature failure and will void the manufacturers’ warranty. Consider the size area you want your garden to be prior to making a lighting purchase. It is better to grow into a fixture than out of one.
Do I need to wear gloves when handling an HID light bulb?
Manufacturers do not state that gloves are required when handling their lamps. It is recommended that your hands be thoroughly washed prior to handling HID lamps though. The oils and smudges from your hands on the lamp can reduce its effectiveness.
A lamp that operates on the opposite ballast it was originally designed for. For example, a 940 watt conversion lamp is an HPS lamp that runs on a 1000 watt Metal Halide Ballast. There are also MH lamps that are designed to operate on HPS ballasts. These bulbs allow the grower to purchase the ballast of their choice and offer the flexibility of growing a variety of plant types by simply changing the lamp they need.
It may take HID or T5 fluorescent 10-15 minutes to come to full brightness.
HID: During the first few hours of use, the light from the lamp will oscillate.
HID: The light will decrease in intensity during the life of the lamp. This will vary by brand & type.
HID: During the first hours, intensity of the light may fluctuate somewhat, which is normal. However after it reaches
100 hours of “burn in” time, will continue evenly the remainder of it's life (with normal aging reduction).
Both: Average life of a MH (metal halide) lamp is 12,000 hours for a 1000 watt lamp and 20,000 hours for a 400
watt lamp. Most users choose to replace lamps before they cease to operate due to lumen loss and spectral shift.
T5 fluorescent lamps offer a rated hour life of 20,000 hours and have a much slower lumen loss and spectral
shift than HID lamps.
Sun System® Lighting Fixture Questions & Answers
Which Sun System® Reflectors have built-in socket assemblies?
• Super Sun® 2 • Cool Sun • Econowing
• Cool Sun XL • Cool Breeze 6” & 8” • Agrotech
• Sun Tube 6” & 8” • Yield Master II 4” • Great White 6”
• Light Pipe 6” & 8” (socket, no lamp cord) • Yield Master II 6” Supreme & Classic • Magnum XXXL 6”
• Super Sun® • Adjust-A-Wing (w/ or w/o lamp cord)
No! BT-56 was the standard for many years. The reduced jacketed BT-37 will provide the same intensity and color that a BT-56 lamp provides. BT-37 is a physically smaller lamp
and is easier to ship and handle.
MVP stands for Multi-Volt Powercord This is Sunlight Supply’s exclusive detachable power cord feature. Simply plug the 120 volt power cord into the ballast and it will run on
120 volts. Want 240 volts, plug in a 240 volt power cord (sold separately) into the ballast and it will run on 240 volts. This feature is available on the Sun System® 1, Sun System®
6 and Sun System® 7.