Best Ceramic Metal Halide (CMH) Grow Lights: A Buying Guide & Review
Last Updated on May 5, 2022 by Gary Stephen
Every grower knows how important grow lights are for indoor gardening. When you are cultivating in tents, rooms, or a greenhouse, you do not have the luxury of sunlight. Thus, it is instead your duty to recreate the natural environment for your plants. When it comes to the CMH grow lights, you would have likely already heard of ceramic metal halides. This CMH grow light is one of the most popular choices nowadays.
But, how much do you know about CMH? How good are they for your plants? Are they suitable for your needs?
In this article, we will discuss to you the valuable facts about ceramic metal halide grow lights. Moreover, we also took the liberty to present to you some of the best CMH products in the market today. So, let’s dive in!
What are CMH grow lights?
Ceramic metal halide, or CMH in short, is a newer variation of the metal halide lamps. This improved version uses ceramic rather than the traditional quartz. By using a ceramic material, it enables the lamp to operate at a higher arc tube temperature.
In that manner, it increases its performance efficiency by 10% to 20% higher than older MH lamps. To add, the quality of the color shift and its spread stability is also enhanced. CMH also has better rendering at 80-96 CRI.
So, how does a ceramic metal halide work?
The arc tube in the CMH grow lights contains a starting gas. Gases such as argon, mercury, and metal halide salts fill in the ceramic tube. During the operation, the temperature of this tube can reach more than 1,200 kelvins. Because of that intense heat, partial vaporization of the MH salts occurs. Thus, dissociating the salts into metallic atoms and iodine.
The gas mixture enables the ballast to deliver a high starting voltage. This combination needs to ionize first before the current can flow through. Thus, powering the lamp.
The metallic atoms are the primary source of light in CMH. It produces a bluish light with a CRI of up to 96. This kind of light is like that of natural daylight. The actual color though will vary depending on the specific mixture of MH salts used.[amazon box=”B014263RJI,B076H8ML3C,B00HXOJ1FG,B01LQZDVD0″ template=”table”]
What is the difference between ceramic metal halide and other competing bulbs?
CMH grow lights versus MH
Although both use the same technology, MH and CMH are different from one another. For that matter, it is not possible to run both bulbs in the same system. Each uses its own setup and specific ballast to function.
When it comes to application, the CMH is more suitable to use across all stages. But, the quartz metal halide is better known to be effective for vegging. Even so, the difference is very subtle.
The only big advantage of quartz metal halide over CMH is its cheaper price point. It is far more affordable considering as well its 50% lesser usable lifespan. Thus, justifying the lower cost.
CMH grow lights versus HPS
HPS or High-Pressure Sodium is very similar to ceramic metal halides. That is because both systems use the same bulb technology. But, there are slight differences worth considering.
While CMH has a more balanced spectrum, HPS produces more red light. Thus, the HPS lamp is more recommended to use during the flowering stage of the cultivar.
Other than that, CMH is still more efficient and has a longer lifespan. That is the reason why HPS has a more reasonable price point too.
CMH grow lights versus LED
Although comparable, LED is a notch higher than the ceramic metal halide lamps. LED or light-emitting diode lamps are more energy-efficient and it generates less heat. This enables growers to operate LEDs for a longer period of time.
The same with CMH, LED is suitable to use on all the stages of plant growth. One downside of using this type of grow light though is its premium cost. It is much more expensive than CMH and any other types of bulbs.
CMH grow lights Comparison
|Best for vegging||Best for flowering||All phases|
Are CMH grow lights good for growing plants?
Ceramic metal halides are best known for their wide spectrum coverage. This means that it has the capacity to deliver a good array of light wavelengths. For plants to grow, they would need the wavelengths between 400 to 700 nanometers. This range will provide the plants all the energy it needs to undergo photosynthesis.
In particular, the plants best absorb blue and red lights. The cool blue light, having a wavelength of 430 to 450 nm, is best for encouraging vegetative growth. Meanwhile, the 640 to 680 nm red light is essential for flowering and fruit production.
CMH also encompasses green and yellow light. This falls between the range of 495 to 590 nanometers. These light colors aid in the photosynthesis process of the cultivars. Also, this specific spectrum is likely reflected. Thus, it renders the green coloring of the plant itself.
It is good to note that the CMH bulb is capable of delivering both ends of the light spectrum. Making this lamp likely applicable to use throughout all the stages of the cultivars growth.
How far should the distance be between the CMH grow lights and the plants?
The advantage though with CMH is that they are being meant for universal positioning. In this case, you can install them both in a horizontal or vertical position. Either way, it will not affect the light distribution and absorption rate of the plants.
What you should focus more is on the correct height and distance of the CMH lamp from your cultivars. Doing such will ensure that your plants will get the optimal benefits from the light. At the same time, it will also reduce the risk of overheating them.
In general, CMH lights should have an average of 3 feet distance above the canopy. This hanging height provides an efficient and even light distribution across the plants. Moreover, this gap is also enough to make sure that hot spots will not develop.
With regard to coverage, the area it can accommodate is dependent on the light bulb’s wattage. For example, a 315W CMH bulb is likely to cover a growing area of up to 4×4. Note here that the higher the wattage, the hotter will be the heat emission. Thus, you should also expect to adjust the hanging height of your grow lights farther up as well.
Here’s a quick reference for the recommended coverage and distance of CMH light.
|Power||Light coverage||Distance from canopy|
|315 Watts||3ft x 3ft – 4ft x 4ft||2ft|
|630 Watts||5ft x 5ft – 6ft x 6ft||3ft|
Are CMH grow lights energy efficient?
In comparison to traditional quartz metal halides, CMH lights are 20% more efficient. CMH is also better at converting electricity into usable light than other types of bulbs. Thus, the increased efficiency delivers optimal power but with lesser energy consumption.
Moreover, CMH light has a remarkable lifespan that can run up to 24,000 hours. That is more than twice longer than the 10,000 hours life expectancy of the quartz MH and even HPS bulbs. Plus, its ceramic arc tube can very well withstand high temperatures. So, they are more durable and resistant to premature breakage.
Given these superior qualities, it is quite expected for its price point to be higher too. Yes, its upfront cost can be quite steep. Then again, its energy efficiency and longer lifespan can help save you money over time. With all the benefits you can get from the bulb, most people agree that it is a worthy investment for your plants.
Things to consider when buying CMH grow lights
The CMH grow light is often available in 315 watts or 630 watts. The wattage here rather pertains to the dissipation of power. In that sense, the higher the wattage of the bulb, the bigger the area of coverage will be as well.
As we mentioned earlier, a 315 watt CMH lamp will have a light footprint of 3×3 to 4×4. Meanwhile, a 630 watt can well cover a 5×5 to 6×6 grow space.
So, let’s say, the size of your grow tent is 3 feet by 3 feet. Then, a single 315W should be enough to cover your grow area. Another instance, if your tent size happens to be 6 feet by 6 feet. In this case, a single 630W lamp will do you fine. Or, you can also opt to use 2 units of 315W bulbs to cover the entire tent or room.
2. Ballast Compatibility.
The CMH ballast is a device responsible for regulating the electric current in the CMH lamp. Thus, ensuring that the bulb maintains its appropriate brightness throughout its operation. Without it, the bulb might burn too bright and explode. Moreover, controlling the voltage helps the bulb to reach its intended lifespan.
There are different types of ballasts for grow lights. But not all are compatible to use with CMH bulbs. The standard electronic ballast is one of those unsuitable to use. It is not applicable because it produces very high frequencies. But, there are also some exceptions. There are a few high-quality electronic or digital ballasts that can work with CMH lamps. As long as these ballasts come with the right microprocessors to power the ceramic bulb.
Then again, it is still the best and the safest choice to choose a CMH-specific ballast. These are being intended to use with ceramic metal halide grow lights. Thus, you can guarantee its absolute compatibility. It often uses low-frequency square-wave technology. In effect, it minimizes the electromagnetic interferences. At the same time, it also produces a steadier stream of light.
Choosing the right ballast for a CMH light is very tricky indeed. Thus, we recommend getting an entire grow kit instead. This is much convenient and it also eliminates the tendency of incompatibility.
3. Color Spectrum.
CMH has one of the most well-balanced light spectrum in comparison to other types of light bulbs. Thus, it is suitable to use in all the stages of the plant’s growth. But know that even if this bulb produces red light, the amount is not as strong as what the HPS bulb can deliver.
So, what most growers tend to rather do is to use CMH light in the early stages of development. And then, shift to an HPS bulb later on when the cultivar reaches the flowering stage. Doing such transition increases your chances to get a higher yield in the end.
4. Heat Output.
CMH runs much cooler than MH and HPS bulbs, but not as cool though as LEDs. The heat CMH produces is still significant enough to cause overheating in the room. Especially, when your grow space has a low ceiling or enclosed with poor air circulation. In this instance, areas like a small closet or tents are least likely ideal.
The key point when using a CMH is to ensure that your grow room has enough space to promote good air ventilation. In that way, you can avoid the accumulation of warm temperature emitted by the light source.
5. Upfront Cost.
Ceramic metal halide lamps are not the cheapest grow lights in the market. The upfront cost of acquiring a CMH is on the pricier end. But you have to look beyond that and instead consider its superior advantages. It has strong qualities like energy efficiency, wider light coverage, and longevity. Taking these into account justifies the initial cost of the product.
Our top picks for the best ceramic metal halide systems
After thinking through the considerations, you might now be ready to buy your own CMH grow lights. But, if in any case, you are wondering which CMH product to choose, don’t worry we got you covered.
Here are our best picks for ceramic metal halide grow lights.
1. Best overall:
Sun System LEC 315W Light Emitting Ceramic Metal Halide Fixture
- Operates with 315W CMH lamps.
- Runs at 208/240 voltage.
- All-in-one construction.
- Reflector hood with German aluminum insert.
- Includes a CDM-T Elite Agro lamp.
- Uses low-frequency square wave ballast.
- 1-year warranty.
- The price point is steep.
Why we like this product:
Sun System is a well-established name in manufacturing quality horticultural products. This US-made grow light kit is not the cheapest in the market. But then again, you can never go wrong with such a reputable brand.
The fixture comes with an all-in-one hood construction. This means that the ballast is already built-in. Making it secured and appear more compact. The electronic ballast in itself has a rated lifespan of 50,000 hours.
The inside of the hood is being lined with 98% reflective German aluminum and 95% textured corners. This feature allows for more uniform diffusion of light across the plant canopy. In general, it can well-cover a 4×4 grow space.
This grow light kit already includes a 315 watts CDM-T Elite Agro lamp. Moreover, the LEC 315 driver comes with built-in thermal protection for added safety.
Grow Co. 630W CMH System with Philips 3100K Full-Spectrum Bulb
2. Best for value:
Grow Co. 315W Ceramic Metal Halide Fixture
- Operates with 315W CMH lamps.
- Uses low-frequency square wave ballast.
- Fully-sealed ballast housing.
- Highly-reflective hammer tone aluminum reflector.
- Includes a 120V power cord.
- 2 years warranty.
- It does not include the CMH lamp.
Why we like this product:
The Grow Co. 315W Ceramic Metal Halide fixture is one of the most sought after CMH products in today’s market. It features a low-frequency square wave ballast contained in a sealed housing. Having such ensures secure placement of the ballast within your fixture.
The package also includes an aluminum reflector. It has a hammer tone finish that further enhances its reflectivity. Thus, delivering even more distribution of light and lessening the formation of hotspots.
This system accommodates one 315W CMH bulb. The listing does not include the light bulb yet. But, there is an available option to include one for an extra cost. If you choose so, Grow Co. has tied up with Philips to provide a 3100K full-spectrum bulb in the kit.
Vivosun 315W Ceramic Metal Halide CMH/CDM Grow Light Fixture
3. Best light bulb:
Philips Master 3100K Green Power Elite Agro 315 Watt CMH Lamp
- 3100K color temperature.
- 1.95 PPF (Photosynthetic Photon Flux) per watt per second light source
- 33,000 initial lumen output.
- 20,000 hours lifespan.
- 315 watts of energy consumption.
- Operates in a low-frequency square wave ballast.
- Price is expensive than competing brands.
Why we like this product:
Philips is a household name everybody has heard of already. This multi-billion company offers a vast range of lights. From domestic to commercial, and even horticultural, name it and they have it. The brand has earned its unwavering success because of its excellent quality products.
The Master 3100K is one of Philip’s most popular CMH lamps. It has long been a favorite of many indoor growers because of its high PPF of 1.95 per watt per second. PPF refers to the number of active photons reaching a specific surface area per unit of time. So, the higher the PPF, the more it will likely benefit the plant in its photosynthesis.
This 315-watt bulb produces an initial output of 33,000 lumens. After 8,000 hours of use, the light output still maintains at 90% or 30,000 lumens. Moreover, it comes with a color temperature of 3100K. This resembles the broad natural sunlight which is great for all plant stages. A 4200K bulb temperature is also available. This is more apt to use on the vegging stage of the cultivar.
Protopia CMH 315W 3000K Grow Light Bulb
4. Best CMH Ballast:
Phantom II E-Ballast 315W CHM 120/240V
- 315 watts low-frequency square-wave digital ballast
- Remote operation.
- Multi-voltage capability (120V/208V/240V).
- Suitable for vegetative and flowering stages.
- With internal radio frequency shielding.
- Features a patented lamp depreciation control.
- Has multi-aspect protection circuitry.
- Wall-mount installation.
- Includes an 8-feet 120V power cord.
- 3 years warranty.
- Less durable.
Why we like this product:
If you prefer to set up your own CMH grow light, this ballast is a very good option to use. This digital ballast is compatible to use with a 315-watt ceramic metal halide lamp. It can be wall-mounted near the hood. Or, up to as far as 50 feet away using optional extension cords.
The device has multi-voltage capabilities. Thus, you can opt to run this either in 120, 208, or 240 input voltage. Though, the package may already include an 8-feet long 120V power cord.
The Phantom II features a multi-aspect protection circuitry. This prevents incidences such as short or open circuits, under or overvoltages, etcetera. To add, the package also comes with a 3-year warranty for added security.
Green Power Luminaires 630 CMH Remote Ballast There you go! The ceramic metal halide grow light is an excellent choice for indoor gardening. Its wide spectrum of light makes it suitable to use all throughout the grow cycle of your plants. Thus, sparing you the hassle and extra cost of changing bulbs on every stage.
Yes, it may be expensive and finicky with the ballast. Then again, the quality of its performance supersedes the disadvantages. Moreover, its remarkable lifespan is way beyond any other light bulbs can offer. In the end, this contemporary grow light is still worthy of an investment.