Your Guide to Ceramic Metal Halide Grow Lights

By Monica Mansfield
Published: January 31, 2014 | Last updated: June 14, 2022 06:12:13
Key Takeaways

Not only do ceramic metal halide lights provide plants with a wide lighting spectrum, they use fewer watts and produce less heat than other types of lighting.

Caption: Ceramic Metal Halide Lights in a Commercial a Grow Source: Canna Obscura/Shutterstock

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?

Ceramic metal halide light bulbCeramic metal halide light bulb. [Source: Stocksnapper/Shutterstock]
Ceramic 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

Ceramic metal halide ceiling lampCeramic metal halide ceiling lamp. [Source: nubephoto/Shutterstock]
The money you save on your power bill is the No. 1 perk of switching to ceramic metal halide grow lights. Although the initial cost of the system is more expensive than other HID systems on the market, ceramic metal halide 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.

Low heat output of CMHs make them an ideal choice for small grow spacesLow heat output of CMHs make them an ideal choice for small grow spaces. [Source: Uladzik_Kryhin/Shutterstock]

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?

Finally, ceramic metal halide 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.

The 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.

Read also:

The Drawbacks of CMH Lights

Professional Grade Grow Room Glasses - Anti UVProfessional Grade Grow Room Glasses - Anti UV. [Source: marin_bulat/Shutterstock]
There are two main drawbacks to ceramic metal halide 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 ceramic metal halide 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.


Share This Article

  • Facebook
  • LinkedIn
  • Twitter

Written by Monica Mansfield | Homesteader, Owner & Writer of The Nature Life Project

Profile Picture of Monica Mansfield

Monica Mansfield is passionate about gardening, sustainable living, and holistic health. After owning an indoor garden store for 5 1/2 years, Monica sold the business and started a 6.5-acre homestead with her husband, Owen. She writes about gardening and health, as well as her homestead adventures on her blog at

Related Articles

Go back to top
Maximum Yield Logo

You must be 19 years of age or older to enter this site.

Please confirm your date of birth:

This feature requires cookies to be enabled