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Ceramic metal-halide bulbs are the grow lights of the future.At least that’s what I keep hearing. Personally, I’m partial to LED technology, but I can’t deny CMH’s appeal.
But before we get to the pros and cons of LEC (Light Emitting Ceramic) lights, I just want to cut to the chase and give you our picks for the best CMH system. I’ll also give you our choices for the best bulbs, since it’s always good to have a backup and you’ll need a replacement eventually anyway.
Note that I said CMH system. I definitely recommend you buy a complete kit. Not only does it save money over buying the components individually, it also ensures that all the components are compatible. Compatibility can be especially problematic with the ballast. More on that below.
Best Complete CMH Grow Light Kits
- Best Overall Kit:Sun System LEC 315
- Best Budget Kit:Grow Co 315W System
Best CMH Grow Bulbs
- Best Overall Bulb:Philips Master CMH Lamp
- Best Budget Bulb:Protopia CMH Lamp
You’ll find in-depth reviews of these kits and bulbs below.
What Is A Ceramic Metal Halide Grow Light?
First, let’s clear up a point of confusion. I’m sure you’ve seen (even just in this article), several different terms and abbreviations. Ceramic Metal Halide (CMH), Light Emitting Ceramic (LEC) and Ceramic Discharge Metal Halide (CDM) all refer to the same thing. CMH is the most common term.
Another point of confusion concerns their relationship to metal halide lights. CMH bulbs are a variation of MH bulbs, but they are quite different. Instead of using a quartz tube, they use a ceramic tube (more here), similar to an HPS bulb.
This allows a higher arc tube temperature, which in turn allows a better mix of gases to produce a more optimal spectrum (more on this below in the sections comparing CMH to MH and HPS). The light produced by a CMH bulb is much closer to natural sunlight than either MH or HPS (with a CRI of 96). It is, for practical purposes, a perfect combination of MH and HPS in a single bulb.
Advantages of CMH
Spectrum
The CMH spectrum combines the red-heavy HPS spectrum with the blue-heavy MH spectrum in one bulb, making it the perfect light for all stages of growth. With a high CRI, it is extremely close to natural sunlight, which is great for your plants and for your eyes (plants look more natural, making it easier to spot any discolorations or other issues).
Efficiency
CMH bulbs give you a much higher PAR output (the amount of light that is usable by plants) per watt than any other type of lighting, apart from the most expensive LED grow lights.
UV Light
The CMH spectrum also contains UV light of all type. Since UV-C light is harmful, the bulbs use a glass filter to block that range, leaving only UV-A and UV-B light, which many feel is beneficial to yield quality. There is no need for supplemental UV bulbs when using CMH lighting.
Lower Heat
CMH bulbs run much cooler than their MH and HPS counterparts, reducing, or even eliminating, the need for additional cooling equipment. They run hotter than LED lights, though.
Long Lifespan
CMH bulbs last much longer than other HID or fluorescent bulbs. The standard rule of thumb for MH or HPS bulbs is to replace them after 10,000 hours of use. Good CMH bulbs last over 20,000 hours. Moreover, they still retain 80% or more of their initial output after 20,000 hours. HPS and MH bulbs deteriorate much more quickly.
Disadvantages of CMH
Higher Initial Cost
A ceramic metal halide grow light system costs, on average, twice as much as a comparable HPS/MH system. Of course, you will easily recover that cost within a year or two, since CMH bulbs don’t use as much power to generate the same output and don’t create as much heat either, resulting in lower cooling costs. You also won’t need to change bulbs as often. All of this is reversed when compared to LED (see below).
Heat Output
I know this is also listed as an advantage above. CMH emits much less heat than HPS or MH, but still more than LED.
Flowering
CMH bulbs are very good at flowering, especially those with a warmer color spectrum (around 3000K), like the Philips 3100K bulb we recommend. That said, HPS bulbs are better, since they contain even more red spectrum light. The problem with HPS is the lack of blue light. They are not good at vegging. CMH bulbs work great for the whole grow cycle.
Ballast Compatibility
Most standard electronic ballasts, the kind you would use for other forms of HID lighting, can not be used to run a CMH bulb. These ballasts have very high frequencies, which make them incompatible with ceramic discharge metal halide bulbs.
There are some high-end electronic ballasts that have the right microprocessors to power CMH bulbs, but your best bet is to use only ballasts specifically designed for CMH systems. These square wave ballasts are better anyway. They produce a steadier stream of light and use a much lower frequency, which has the added benefit of reducing RF interference to the point that it is virtually nonexistent.
As stated above, the easiest and most cost effective solution is to just buy a complete CMH kit to start with. That way you won’t have to worry about the compatibility of your ballast at all.
How Do CMH Grow Lights Compare To HPS, MH And LED?
You’ve probably noticed that some of the points above were both advantages and disadvantages. That’s because CMH lights generally fall in the middle between traditional HID and LED.
CMH vs. HPS
HPS bulbs have a spectrum that is very heavy in reddish/orange light, but contains almost no blue. This makes them ideal for flowering, but not great for vegging. Using an HPS bulb during vegging results in weak, spindly plants.
CMH bulbs are great for flowering, too, but not as good at HPS. They are much better at vegging though, making them the perfect full-cycle bulbs.
CMH lamps are generally a bit more expensive than their HPS counterparts, but they make up for it with double the usable lifespan. They also use less power and emit less heat.
CMH vs. MH
As previously mentioned, although ceramic discharge metal halide bulbs are derived from metal halide bulbs, they are very different and they can not be run in the same system. They need a different ballast.
Metal halide bulbs are slightly better at vegging than CMH bulbs, but the difference is minimal. And it is debatable, at that. The added red light is actually a benefit, even during vegging.
As a result, the only real advantage of MH bulbs is a lower cost. That said, they only have half (or less) the usable lifespan of a ceramic metal halide bulb, so that easily makes up for the cost difference.
CMH bulbs also use less power than MH and emit less heat. There is basically no reason to go with MH over CMH, unless you already own the appropriate fixtures and ballasts.
CMH vs. LED
This is where things get a little more complicated. If you are comparing CMH to high-quality LED grow lights, then all of the advantages CMH has over traditional HID bulbs are now disadvantages when compared to LED and vice versa.
CMH emits more heat, uses more power and has a shorter lifespan. On the flip side, the initial cost is much lower. Good LED lights also have a light spectrum that is perfectly tailored for plant growth, easily beating even the sun-like CMH spectrum.
The decision basically comes down to two things: initial cost versus operating cost and yields. Top quality LED lights cost more upfront, but they save money in the long run and result in better growth and yields.
When you compare CMH with cheaper LED lights, the decision is much less clear-cut. Now CMH bulbs are actually more expensive, though not by much. They also outperform cheaper LEDs, but again, not by much.
To me, this decision comes down to three things: one, the purchasing risk of getting a cheaper LED light (it should be fine, but you might get a defective unit and have to waste time returning it); two, the simplicity of LED (you really just need to hang it and turn it on); three, the heat output (even cheaper LED lights emit less heat than a CMH bulb).
Ceramic Metal Halide Grow Light Reviews
Best CMH Grow Light Kit: Sun System LEC 315
The Sun System Light Emitting Ceramic Metal Halide line of lights is by far the best option on the market in 2019. Nothing else really comes close. Naturally, that means it’s a bit more expensive than most competing brands, but if you can afford it, it’s worth the extra cost.
It includes everything you need to light your plants, so you can just plug it in and start growing. You get an all-in-one hood reflector, which means it contains the ballast needed to power the lamp. The bulb socket is at the top of the hood, so the bulb hangs vertically. This makes for a more even light spread than a horizontal bulb.
The inside of the hood is 98% reflective German aluminum with 95% reflective textured corners. This ensures optimal output and uniformity, meaning you are losing as little light as possible from the reflection and there are no hot spots that can burn your plants. It gives you a coverage area of 4 by 4 feet.
Along with the hood, the kit also includes a Philips Master 315W bulb. The kit linked to here includes the 3100K bulb, but there is also a kit available with the 4200K bulb instead. The 4200K bulb is better for vegging, so most growers use it if they are getting a light for the whole grow cycle.
Personally, I think the 3100K does fine with vegging and it’s so much better at flowering, that I would just go with that one for everything, unless I was going to use the light for vegging only. Basically, the increase in vegging efficiency of the 4200K spectrum is more than offset by the increase in yield of the warmer 3100K spectrum.
The Philips bulbs have have an initial lumen output of 33,000 and a very high 1.95 PPF (photosynthetic photon flux) per second. In short, these bulbs give you a huge output considering they only consume 315 watts. Their open rated construction reduces radiant heat from the arc tube. As a result, this kit runs much cooler than a comparable HPS or MH light.
Furthermore, the Philips lamps last a long time, with an expected lifespan of 20,000 hours. More importantly, they retain 90% of their lumen output after 8000 hours of use and still retain 85% of their PPF output after 20,000 hours. It should come as no surprise that this bulb is also our recommendation for the best CMH bulb (see below).
The ballast included in the reflector is a 50/60 Hz low frequency, square wave, electronic ballast, with a rated lifespan of 50,000 hours. Square wave is a newer technology that provides a more constant maximum voltage to the lamp, resulting in a more steady light. Also, their lower frequency means no issues with RF interference.
The whole Sun System CMH kit is covered by a 1-year warranty and there is also a 240 V version available. It gets a Grow Light Info rating of 4.8 out of 5.
Pros
- All-in-one construction -- ballast is built into the hood, making this kit much more compact than others
- Bulb hangs vertically -- more even light spread than horizontal bulb
- Huge output -- given the 315 watt consumption, the Philips bulb gives you a huge 33,000 lumen output
- Long lifespan -- the bulb is rated for 20,000 hours and retains 85% of its PPF output in that time
- Square wave ballast -- no issues with RF interference and a much more steady stream of light
- Low heat output -- this light does not need to be ventilated
- Free ratchet hangers -- a free set of ratchet hangers is included
Cons
- High price -- higher price than competing lights, but, as usual, you do get what you pay for
Best Budget CMH Kit: Grow Co CMH 315W System
The Grow Co Ceramic Metal Halide Lighting System is not the cheapest one available, but it is easily the best of the lower cost options available in 2019. It generally costs slightly more than half as much as the Sun System kit, but contains all the same components. The difference is the quality.
The Grow Co kit is very good, but it still can’t come close to the Sun System kit. The most noticeable difference is the external ballast. Sun System has the ballast inside the reflector, but the Grow Co kit has an external ballast (as do most CMH kits). That said, it is still attached to the reflector. This mainly just makes the system bulkier, but that can be a big concern for some.
Apart from that, it is a low-frequency square wave ballast with a fully sealed ballast housing, so you don’t have to worry about RF interference.
The bulb included with the Grow Co system is the same Philips bulb as the one in the Sun System kit. You can read about that bulb in the Sun System review above or in the bulb review below.
The reflector is made from high-reflective hammer tone aluminum, but the manufacturer does not provide any info concerning the percentage of reflectivity and this is impossible to measure on your own without the proper equipment. Since they do not include this info, I have to assume their reflector is not quite as reflective as the Sun System one.
The Grow Co CMH kit linked to here includes the ballast, reflector, bulb and a free set of ratchet hangers. In other words, the exact components as the Sun System kit. However, Grow Co offer several other options as well.
They have the same kit without the bulb and hangers, they have it with a 240V cord instead of the standard 120V cord and they sell a 630 watt version, in which the reflector holds two bulbs, doubling the effective output. You can get the 630 watt kit with or without bulbs. All Grow Co LEC kits are covered by a 2 year warranty on the fixture and ballast and 1 year on the bulb.
Pros
- Lower cost -- the Grow Co kits costs just over half as much as the Sun System one
- 630 watt option available -- you can double the power with a dual-bulb reflector
- 2 year warranty -- twice as long as Sun System
Cons
- External ballast -- this makes the system a bit bulkier
- Reflector less effective -- the reflector does not reflect light as efficiently as the Sun System reflector, meaning you lose more light
Best CMH Grow Bulb: Philips Master 3100K GreenPower Elite Agro 315 Watt CMH Lamp
If you’ve read everything written on this page so far, you’ll already be familiar with this bulb. It is the one included in both of the kits we reviewed above—and for good reason. The Philips Master 3100K GreenPower Elite Agro 315 Watt CMH Lamp is as good as it gets.
It gives you 33,000 lumen of output, which is incredible for a bulb that only uses 315 watts. Moreover, it retains 90% of that output after 8000 hours of use.
The rated lifespan of this CMH lamp is 20,000 hours and even at that point, it still retains 85% of its initial PPF output, which is an unbelievably high 1.95 PPF (photosynthetic photon flux) per watt per second.
Philips uses a unique open rated lamp construction that reduces radiant heat from the arc tube and makes their bulbs perfect for open fixtures. Simply put, they emit far less heat than comparable HPS and MH bulbs, greatly reducing the need to cool your grow space.
The bulb we’ve linked to in this review has a 3100K color spectrum, which is our preferred bulb to use for all stages of growth. It is a flowering monster and does well in vegging too. There is a 4200K version available as well, the Philips Elite MW 4200K Master Color CDM Lamp, for anyone who plans on only using it for vegging or for those who prefer a full-cycle bulb with more blue spectrum light (to me, flowering performance is the most important).
Pros
- Huge output -- given the 315 watt consumption, the Philips bulb gives you a huge 33,000 lumen output
- Long lifespan -- the bulb is rated for 20,000 hours and retains 85% of its PPF output in that time
- 1.95 PPF/w/s -- incredible efficiency, with very high output per watt consumed
- Low heat output -- this light does not need to be ventilated
Cons
- High price -- higher price than competing bulbs, but as usual, you do get what you pay for
Best Budget CMH Bulb: Protopia CMH 315 Watt 3100K
If you’re looking to save some money on bulbs, there are a lot of options available, considering that the Philips lamps are among the most expensive. Unfortunately many of the cheaper bulbs simply are not very good. An exception is the Protopia 315 watt 31ooK CMH bulb.
In terms of output, this bulb is actually more powerful than the Philips initially, with an output of 37,000 lumen. The problem is that the output deteriorates much more rapidly than the Philips bulbs. In fact, the rated lifespan of this bulb is only 15,000, a full 5000 hours less.
The PPF per watt per second is also lower, at 1.81. This means the bulb is not as efficient as the Philips bulb at turning the power you feed it into usable light output. All that said, given how much less the Protopia bulb costs than the Philips bulb, it is definitely worth considering. It easily outperforms other similarly priced bulbs.
The version we linked to is 3100K, but there is also a 4200K version available. You’ll find it on the same page as the 3100K bulb—simply select the 4K option to check that one out.
Pros
- Low price -- costs considerably less than the Philips
- Huge initial output -- the Protopia beats even the Philips with 37,000 lumen
- 1.81 PPF/w/s -- great efficiency, with very high output per watt consumed (but not as high as the Philips)
Cons
- Faster deterioration -- the bulb becomes less bright much more quickly than the Philips (but similar to most other bulbs)
- Shorter lifespan -- the Protopia does not last as long as the Philips overall
The industry is changing, and competition among growers has become fierce. If you want to keep your edge, you need to stay up to date on the latest lighting technology. This means getting better acquainted with ceramic metal halide (CMH) grow lights.
Ceramic metal halides, also called light-emitting ceramics, are the newest innovation in HID lighting. They bring many benefits to the table, with only a few drawbacks.
What are Ceramic Metal Halide Grow Lights?
CMH metal halide grow lights are made with an arc tube constructed of a ceramic composite instead of quartz or PCA. This allows the tube to reach a higher temperature. To achieve the lower operating temperature in HID lamps made with quartz or PCA, a combination of gases must be used that don’t necessarily produce the optimal light spectrum for photosynthesis.
The higher operating temperature of the ceramic tube allows for an ideal mixture of gases. This creates a fuller spectrum of light that increases the growth, overall health and yield of your plants. A special ballast is needed for ceramic metal halides. Not just any digital ballast will do. CMH lamps require a low frequency, which makes high-frequency digital ballasts incompatible.
Depending on the quality of the system and where you shop, complete CMH set-ups range in price from US$200-$1,100, with an average price of US$550. Most set-ups hold one 315W lamp, but there are some fixtures that hold two lamps for a total of 630W. The lamps themselves cost between US$80 and US$100.
The lamps come in two versions: the 3,100 Kelvins (a full spectrum) and the 4,200 K (a blue spectrum). Manufacturers claim you will only need to replace your lamps every two years.
The Benefits of CMH Lights
The money you save on your power bill is the No. 1 perk of switching to CMH grow lights. Although the initial cost of the system is more expensive than other HID systems on the market, CMH systems will save you money in the long run. Some jurisdictions even recognize them as energy-efficient lighting systems and offer incentives to offset the initial cost.
Some suppliers claim one 315W CMH is equivalent to one 1,000W HPS lamp in terms of yields. Others have reported that you need two 315W CMH lamps to produce the same yields as a 1,000W HPS. The varying reports probably have to do with other elements in the garden and the gardener’s skill level, and the truth probably lies somewhere in the middle. In any case, the general consensus is that your yield per watt is greater with ceramic metal halides, and you will be spending much less on electricity to power your lights.
These lights also have a low heat output because of their low wattage. One watt from a grow light creates about four British Thermal Units (BTUs) of heat that need to be cooled.
Let’s say you have a small room with four 1,000W HPS grow lights. Your four lights alone create 16,000 BTUs of heat that need cooling. If you trade those lights in for four 630W fixtures, which will match, if not exceed, your current yields, you will only create 10,000 BTUs of heat. Your air conditioner won’t have to run as often, and you’ll see savings on your power bill. The low heat output of CMHs make them an ideal choice for small grow spaces, such as closets and grow tents.
Another benefit is that with the ballasts required to run them, you won’t have to deal with the electromagnetic interference (EMI) issues many growers experience with digital ballasts. High levels of EMI from digital ballasts are known to interfere with cellphone service, radio, Wi-Fi and cable television, and the Federal Communications Commission hands out citations to people who violate EMI emission standards.
One final advantage ceramic metal halides bring to the table is their superior light quality compared to other HID lamps, which is due to a few factors. First, they have a wider spectrum than other HID lamps—a result of the near-perfect, unique combination of salts, halides, and gases used in the arc tube.
This mixture creates a spectrum close to that of the sun and emits a stunning, crisp, white light. In fact, the color rendering index (CRI) for ceramic lamps ranges from 90-92. To give you some perspective, the sun’s CRI is 100. HPS lamps range from 20-30, and metal halides range from 60-65. The closer the CRI is to 100, the closer the spectrum is to that of the sun.
In terms of light quality, ceramics include ultraviolet and infrared rays in their spectrum, which plants love. The higher amounts of UV rays create stronger, woodier stalks. This means the growth and vigor of your plants will be unmatched, especially in the vegetative stage. Due to the incredible growth CMHs produce, growers have reported great success when using silica supplements with these lights.
Silica helps with cell division and creates stronger cell walls, which makes the leaves, stalks and branches significantly stronger and better able to withstand the weight of the fruits. As an added bonus, pests don’t like woody stalks because they are too hard to chew on. Compare it to eating a tender, juicy steak as opposed to eating an overcooked, dry steak. Which do you prefer? (Read More: Simply Silica – How to Boost the Strength of Your Plant's with Silicon)
Finally, CMH ballasts use square-wave technology. When you look at the graph on the back of the box your bulb is packaged in, notice the high peaks and low dips. The peaks are an indicator of energy pushing out of the bulb. T
he low dips indicate light trying to travel to the next peak. You can see this with your own eyes when you take photos and videos of your growroom. With most HID lights, you’ll see bands of light on your photos.
The bands of light are the peaks in the graph, and the spaces between them indicate the dips. With square-wave technology, there are fewer dips. A steadier beam of light is produced, which means your plants receive more light over their lives.
The Drawbacks of CMH Lights
There are two main drawbacks to CMH grow lights. The first has already been mentioned, which is the initial cost. If you are like most growers, you probably took the most affordable route when setting up your garden.
However, as your knowledge and experience increase with time, you may see the value in upgrading certain components in your growroom. Quality lighting pays dividends at harvest time. This, coupled with the energy savings over the long term, make the initial cost of CMHs worth it for many growers.
The other drawback is that growers must use extra caution when working in the growroom when the lights are on. Many CMH grow lights come with warnings from manufacturers that suggest growers should not be around the lamps for more than a few minutes at a time while they are on, unless adequate shielding or other protection is used.
This is because if the outer envelope of the lamp is broken or punctured, you run the risk of serious skin burns and eye inflammations from short-wave UV radiation. It is only a potential drawback if you like to work in your garden for extended periods while the lights are on. Alternatively, you can work during the dark cycle.
A green LED headlamp can provide you with light while you prune or water. The green light will not disrupt the plants’ natural rhythms. Another option is to use a reflector with a lens covering the bulb, but the disadvantage of this is reduced light to the plants. It is important to note that, overall, CMH lamps are safe, but it is always better to be safe than sorry.
The bottom line? If you want to keep up with your competition, you should considering making the switch to ceramic metal halide grow lights. You’ll be a happy grower come harvest time if you do.