10 Advantages of Using Ceramic Metal Halide Grow Lights

By Chris Bond
Published: October 25, 2017 | Last updated: December 3, 2017 11:45:57
Key Takeaways

Ceramic metal halide bulbs are not the cheapest way to go for grow light options, in fact they cost many times more than other types. However, the cost on them is dropping, and they last a lot longer. Here are a few more reasons why CMH lamps are worth looking in to.

Source: Urban Flora

There is a growing (pun intended) number of indoor growers that are choosing ceramic metal halide (CMH) bulbs as their lighting of choice.


Also known as Light Emitting Ceramic (a trademarked term that only applies to a particular kind of CMH), or ceramic discharge metal halide (CDM), these types of lamps are a type of metal halide (MH) grow light.

No type of grow light is perfect for every condition and every budget, but there is a growing list of reasons why CMH bulbs are worth looking in to.


Check out these 10 reasons to see if CMH is the way to go for your grow:

Provide broadest spectrum

Ceramic metal halide lamps work by heating up a ceramic tube within the bulb. Ceramic can withstand much higher temperatures than other media typically used in lights. This higher temperature results in the bulb creating a plasma-like light source similar to the sun.

Since the light emitted from a CMH is akin to natural sunlight, its spectrum is closer to that of natural sunlight, so that plants exposed to CMH light are getting a wider range of wavelengths of usable light than other types of grow lights can produce.


Best CRI

CMH lights provide the highest measures of color rendering index (CRI) as compared to other grow lights. Objects that are fully visible in natural, unobstructed light appear to the human eye with a CRI of 100.

Artificial lighting does not reproduce the same light as the sun, but CMH bulbs come very close, with CRI ratings ranging between a low of 80 to a high of 96.


Provide UV Lighting

CMH bulbs, as a function of offering a fuller spectrum of light, provide significantly more ultraviolet light than many other types of grow lights. Plants thrive during their vegetative stages with this type of light and it aids in the development of stronger branches.

Color Stability

Unlike various other types of grow lights, CMH bulbs provide a consistent quality and duration of light throughout their useful life. Many types of grow lights lose effectiveness over time that may not be evident to the human eye; CMH bulbs retain their wide spectrum.

More Efficient

This is subject depending on what is being compared and for the duration that the bulb is in use, but CMH bulbs are up to 20 per cent more efficient than other types of metal halide bulbs. The yield per watt of CMH bulbs is higher.

Longer Lasting

This is another subjective benefit, but CMH bulbs do last longer than halogen and incandescent lights. They have been confirmed to run as long as 24,000 hours (almost 3 years).

Produce Less Heat

Though they operate at higher temperatures, CMH bulbs emit less heat than other types of bulbs. This is important in smaller grow rooms, where a grow light may contribute to temperatures that are too high for efficient growth and yields.

It also means that the bulb itself can be closer to the plant, reducing the chance of burning the leaves which is a possibility with some other types of grow lights.

No Electromagnetic Interference

The ceramic in CMH bulbs does not interfere with electronics such as cell phones or television signals the way that some other types of grow lights or electronic ballasts can. This is not only a convenience, but helps to avoid detection if the intent of a grow room is to keep a low profile.

Fit In Other Fixtures

Switching to a new type of grow light often means purchasing additional ballasts or making other modifications. However, CMH lamps are made in a wide range of sizes so that they will fit into existing halogen fixtures and high pressure sodium ballasts, so long as they are the magnetic and not electronic type.

Cost Is Falling

Ceramic metal halide bulbs are not the cheapest way to go for grow light options. In fact, they cost many times more than other types. As they continue to take a larger part of the market share of grow lighting, their cost is beginning to come down. As CMH bulbs are being produced in greater and greater quantities, their prices should continue to fall.

For more advice on CMH Lights, check out Your Guide to Ceramic Metal Halides.


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Written by Chris Bond | Certified Permaculture Designer, Nursery Technician, Nursery Professional

Profile Picture of Chris Bond

Chris Bond’s research interests are with sustainable agriculture, biological pest control, and alternative growing methods. He is a certified permaculture designer and certified nursery technician in Ohio and a certified nursery professional in New York, where he got his start in growing.

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