Garden & Greenhouse


Grow Light Buyers Guide for the Grow Room

Posted September 16th, 2016 by Robin Nichols in

Are you just starting to grow and wondering what lighting you need for your grow room? Don’t worry; to follow is a breakdown of lighting options as well as some recommendations. Not all of the lighting types are listed, but this list does include the most common grow light options.

Fluorescent Grow Lights

T5 and CFL cfl-grow-lights

Fluorescent lighting is one of the simplest ways to light a garden and is most often used in a grower’s veg room. They are more efficient than HID lights and as a result product less heat. The most common fluorescent grow lights are T5 grow lights and CFL grow lights.

T5 Fluorescent grow light fixtures for indoor gardening are all-in-one systems. This means no external ballast is needed and they have built in reflectors. In most cases they will come with bulbs installed and may even offer a grow or bloom version.

CFL grow lights for indoor gardening are usually either smaller 25w medium base socket (standard light socket) or 125w CFLs. Be sure to purchase industry specific lighting and not just standard lighting found in supply stores. Indoor gardening industry CFLs are self-ballasted, meaning they screw into a CFL reflector and are ready to go. Most cheap 125w CFLs found at general lighting supply stores have a non-ballasted bulb because they are designed for outdoor lighting fixtures with a built-in ballast.

The trade-off for the simplicity and lack of heat comes in the form of less usable plant growth specific light and less light penetration. Many growers use fluorescent lights for veg growth only or as supplemental lighting in the flowering stage. It can produce lackluster results as the primary light source during the bloom stage due to the lack of light penetration. If you use fluorescents for the flowering stage, a canopy growing method like a screen of green should also be used. This helps maximize the fluorescent lighting and reduces the need for penetrating light.

HID Grow Lights

Metal Halide (MH) or High Pressure Sodium (HPS) Lamps*

Both MH and HPS fall under the High Intensity Discharge (HID) grow light category. HID grow lights require a reflector/fixture, bulb and ballast. These pieces are sold separately unless they are included in a kit. metal-halide-lampOccasionally a fixture will have an integrated ballast.

MH lamps produce a blueish to yellow spectrum that is especially suited to the vegetative/growing stage of plant growth. HPS lamps produce a red/orange spectrum that is especially suited for the blooming/budding stage of plant growth. Metal Halide is the better option if your plants are in the vegetative stage. And High Pressure Sodium is the better option if your plants are in the bloom stage. If you can only have one bulb, typically you will want to pick a HPS lamp since the blooming yield is the more important aspect. Both MH and HPS bulbs are less energy efficient and produce a significantly higher amount of heat than LED or fluorescent fixtures. But they also generate better usable light than fluorescents and are more affordable than LED grow lights.

Dual Arc Lampsdual-arc-lamp

Dual arc lamps are another bulb type for HID lighting. While a dual arc lamp is technically a HPS lamp, dual arc lamps contain both bulb type components and emit a more natural, fuller light spectrum. For example, a 1000W dual arc lamp contains a 600W HPS component and 400W MH component.

Double Ended Lamps (DE)

Double Ended Lamps have gained popularity in the past couple of years. Voltage is generated at both ends of the lamp to ensure a more even burning of gases inside the tube and a more stable spectral output. This allows them to have a 10% increase in light intensity and PAR output over traditional HPS lamps. DE lamps also emit more UV and IR light (over traditional HPS), which increases potency and essential oil production in plants. These bulbs degrade more slowly than traditional HPS lamps, so a double-ended lamp will still be putting out 90% of its original intensity after 10,000 hours. DE grow lights still need a ballast, lamp and reflector, like standard HID lighting, but they are more commonly available in all-in-one reflector/ballast units than regular MH/HPS grow light setups.

The trade-off for Double Ended grow lights is they can’t use traditional HID hardware. DE grow lights require specific DE reflectors, DE exclusive or compatible ballasts and specialty DE grow light bulbs. The grow room setup will also need open reflectors because most DE reflectors are open with no cool ports or glass. This is due to the glass filtering out a large portion of the UV and IR that the DE grow light emits; making an air cooled DE grow light not much better than a standard HPS grow light.

Ceramic Metal Halide (CMH)

ceramic-metal-halide-lampCeramic Metal Halide grow lights (sometimes referred to as LEC or CDM) are the most recent technology to light gardens. They have a very broad light spectrum and emit UV. This makes their light more similar to natural sunlight when compared to traditional HID lamps. CMH grow lights are often used as primary vegetative stage lights, primary lighting for SOG applications, or as supplemental full spectrum in larger grows. CMH grow lights are 10-20% more efficient than a traditional MH and have increased PAR to Watt when compared to traditional HID grow lights. CMH lamps tend to have a longer life than traditional MH lamps. They can last up to 24,000 hours (with 87% of its original intensity at 20,000 hours) vs. traditional 16,000-20,000 hours (with 50% intensity lost after 10,000 hours) for MH lamps.

While it isn’t a factor for plant growth, some people think it’s important to include the CRI (Color Rendering Index) rating for lamps. CMH lamps are generally in the 80-96 CRI range (where the sun produces 100 CRI). Like DE grow lights, Ceramic Metal Halide grow lights use open reflectors and are often sold as all-in-one units. A CMH grow light setup consists of a specialty bulb, reflector and ballast. They also have a special socket and require a special CMH reflector and ballast. While some growers are reporting success using CMH grow lights during the flowering stage, we don’t recommend CMH in place of 1000w or 600w HPS grow lights.

LED Grow Lights

LED Lightingled-grow-lights

LED Grow Lights are one of the most efficient lighting options available, and arguably one of the best if one of the latest high-end LED grow lights is being used. This is only applicable for high-end LED grow lights because some of the less expensive LED grow lights still use older technology. This includes weaker/lower wattage LED diodes, among other issues. These lights typically aren’t good for anything more than the vegetative stage of plant growth. If you are just growing crops like greens or lettuces, herbs and lower light plants you’ll probably do fine.

Grow Light Comparison of HID vs LED vs Fluorescent

Generally speaking, HID is currently the most popular type of grow lighting. However, due to their greater energy efficiency and growing technology, fluorescent and LED fixtures are quickly gaining ground. HID light setups are usually less expensive to purchase but are more expensive to operate. They generate a lot of heat and use a lot of electricity which increases electric costs as well as equipment costs like air conditioning. To help give a comparison we’re going to break it down by growth stages.

Seedlings/Clones Stage

Seedlings and clones don’t need much light, and the light they need should not be very intense. The most common propagation lighting that we see used, and recommend, are fluorescent grow lights. Fluorescent grow lights produce enough light to grow the young plants but it isn’t too harsh to burn their delicate leaves and they don’t create too much heat. After fluorescent grow lights, LED has become the second most popular method that we see. This includes the basic LED grow lights like the ones that screw into a household light socket, strip lights, and ufos. It does not include the more expensive LED lights with the new technology.

The least recommended grow light for propagating seedlings or clones would be HID (Metal Halide). This is due to the excessive heat generation and light intensity. For the most part, using HIDs is overkill for propagation. Using a 150w MH 3 feet above seedlings will probably be okay. Everything else is overkill and will probably hurt the plant more than help it, unless the lamp is attached to the ceiling. For overall performance while accounting for cost and efficiency we’d recommend fluorescent grow lights. A 125w CFL, a basic reflector and light hangers are typically a little less expensive than a 2 tube 2 foot T5 fixture. If you can find inexpensive vegetative LEDs you can build a great little propagation setup as well.

Vegetative Stage

The vegetative stage of plant growth is time to have more intense light. Fluorescents are still commonly used, though with larger fixtures and more bulbs. LEDs are great for the vegetative stage too and even the older; low-technology LEDs do a decent job during this stage. Many growers have moved their older LEDs that aren’t well suited for the flowering stage to their vegetative room and experienced good results. HID Metal Halide grow lights have been the gold standard for the vegetative stage for the past few decades. They produce good results and can be used with larger plants that less intense lights like fluorescents. Ceramic Metal Halide is becoming popular and is praised for its performance during the vegetative stage of plant growth well.

All lighting types have their place during the vegetative stage of plant growth. Fluorescents are inexpensive and efficient. LED grow lights, even the cheap ones, work great in this situation. They give you a long-lasting light that doesn’t degrade, but do have a higher initial cost. The tried and true HID grow light is always a good way to go. Even with an inexpensive bulb, they offer excellent performance during this stage. Ceramic Metal Halide is another great option as well.

Bloom Stage

The bloom stage results are where all of your hard work pays off. For blooming we typically do not recommend fluorescent grow lights. Can you bloom under T5s? Yes. Can you get good results? Sometimes. For best results with T5s you need grow at the canopy level only, trimming off everything below. T5s don’t have penetration to grow the lower portions of the plants to their full potential and waste energy that could have been focused at the canopy. If you do that you’ll get some good results, otherwise your results may be a little airy rather than dense.

Some good quality LED grow lights can work magic in bloom. Due to the wide array of spectrums we’ve seen some very dense, frosty and sticky results from LEDs that some other lighting types just can’t do. Some growers will argue that HPS is the best and that they will produce a larger harvest than LEDs. The answer to this is maybe, but how about the quality? Does it look like you just sprayed it with a can of that spray-on Christmas tree snow? The cost of LED grow lights is much higher initially than other light options but you pay less for energy, cooling, fans, bulbs, etc.

HID lighting, specifically HPS grow lights, is the preferred bloom lighting for most grow rooms. Their lower initial cost and consistently good results make them ideal for most growers. High-end bulbs produce even better and the use of specialty bulbs, like finishing spectrum bulbs, can boost results even more by adding more of the frosty quality that wide/multi-spectrum lights like LEDs offer. Some growers are also using Ceramic Metal Halide for their bloom grows, though they perform better as vegetative stage lights than bloom.

There is no clear winner in our recommendation as there are many trade-offs and differences, with some being the preference of the grower and their style. T5s are our least favorite for this stage. But if they are used properly with a canopy scrog, they can provide good results. Due to the ease and affordability T5s can be a good option, just be sure to grow it right.

High quality LED grow lights are one of our favorite bloom stage recommendations. Their downside is that the high initial cost can be a problem for many growers, especially new ones. Spending over $1,000 initially on a grow light can be difficult unless you have the extra cash and are sure you are going to stick with the hobby or business. We recommend traditional HPS lighting for most growers, especially newer growers that want good results at an affordable price. HID lighting is affordable and even low-end bulbs can produce excellent yields. The trade-off is that you have to replace bulbs at least yearly; due to the inefficiency the lights draw high wattage and generate more heat than other lighting types.

Grow Light Wattage Footprints [Air Cooled (AC) and Open]

Listed below are some common recommendations for lighting based on the grow room footprint. The recommendations are based on the square footage with recommendations for Air Cooled (AC) grow lights and open reflector grow lights. Recommendations are based on a home ceiling of about 7′ or grow tent height. Extended height grow tents or high ceiling grow rooms may be able to use higher wattages than the provided recommendations. You may see growers using higher wattage grow lights for certain sizes than the below recommended wattages. Using higher watt grow lights may require additional cooling for the space due to the extra heat and is not recommended for a new grower.

Grow Room Footprint

Size in Square Feet


Air Cooled Grow Light Recommendation in Watts


Open Reflector Grow Lights in Watts
2 x 2 250 150
2 x 4 400 250
3 x 3 400 250
3 x 5 600 400
4 x 4 600 400
5 x 5 1000 600
4 x 8 2 x 600 2 x 400
8 x 8 4 x 600 4 x 400
5 x 10 2 x 1000 2 x 600
10 x 10 4 x 1000 4 x 600
8 x 16 8 x 600 8 x 400
10 x 20 8 x 1000 8 x 600

Background information for this article was provided by Rogue Hydro. Learn more about them at

*A Note Concerning the Term Lamp: The lighting industry refers to certain light bulbs as lamps. This is because bulbs like metal halide, high pressure sodium and fluorescents are technically lamps. They use gases to burn rather than a filament, making them a lamp and not a bulb by definition. Most people call them bulbs either way. Most grow store employees will understand what you mean when you say “bulb.” Just make sure you clarify “grow bulb” if you are in a more generalized store.

Want more information? Read these articles:

7 Keys to Success with LED Grow Lights

Are CFL Grow Lights Effective?

Comparing T5 and T8 Grow Lights for Indoor Gardening

How LED Grow Lights Have Changed and Can be Used by Today’s Grower

Why High Intensity Discharge (HID) Grow Lights Remain Popular

Understanding Hydroponic Grow Lights

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