CMH vs Double Ended Grow Lights
One question that seems to be coming up over and over is, "Which light is better: a CMH light or a double ended light?" Both lights fall under the category of high-intensity discharge (HID) light, but that's about where the comparisons stop. Each type of light offers different advantages and disadvantages to your grow, and we'll be going each so you get a better idea of what works best in your indoor garden.

What's an HID Grow Light?

Several oranges cut in half
Before we dive into CMH and Double Ended grow lights, let's talk about the type of grow lights these are: High-Intensity Discharge lights. No matter the material used to give you light (gasses, metal halides, or sodium), HID's use an electrical arc tube to heat elements inside your bulb. The materials and how hot they're allowed to get will determine what color and brightness of light you see when your lights are on. Whether you're working with a ceramic base or wired bases like DE's, if it uses elements and an electric arc to produce light it's more than likely an HID. Knowing that these are all HID's, anyone looking at either of these lights (or even single ended lights) should know that there's going to be heat generated by these lights. That means you're going to be battling high temperatures and humidity even more than you would with T5 fluorescent lights and LED grow lights.
We haven't scared you off from HID's, have we? Trust us, we love all HID's, but for growers getting into this for the first time, it's a good idea to think of heat accumulation. "Will I have enough room and/or equipment to keep my growing area at a good temperature? Will I need to move into a tent from my closet?" All of that heat will need help getting out of that space, too, so that means more fans and equipment running to combat heat. Still with us? Good, because even though it might get a little tricky eventually, growing using HID's is tried and true. Even better, DE's and CMH's will give you a much higher light output than their single-ended counterparts. Now that you know what you'll be getting yourself in to, it's time to start putting these lights to the test for your grow room.

Double Ended Grow Lights

Double ended grow light
Double Ended grow lights
are just like the HPS and MH bulbs you know and love, only they're much brighter than their single-ended counterparts. If you check out these bulbs you'll see that they're much skinnier than standard HID's and they don't screw into a socket. Due to the structure of the bulb, it doesn't have to be as large to house the arc tube and its elements, thus it will get the same amount of light and more simple because of its design.
Fan and plants in a grow tent
Single-ended bulbs
have a long, metal wire frame that goes from the base to the end of the bulb. That metal frame houses the arc tube that contains the material needed to give you light, from metal halides to sodium. All of the framework a single ended bulb will often hinder the spread and intensity of your bulb. The framework of DE bulbs is much simpler and allows for more light down on to your plants. Instead of your bulb being lit from the socket of your reflector, there are wires on each end of the bulb that slide right into the fittings of the reflector (sort of like a T5 grow bulb). This allows for three things: 1) The bulb doesn't have any metal blocking the arc tube, thus all the light it gives off is unhindered 2) The bulb will fire faster and receive put out more light because it receives energy from not just one end, but two 3) The light you get will be spread more evenly across your canopy than other lights.

CMH Grow Lights

Grow tent with plants and a hanging grow light
Ceramic Metal Halide (CMH) grow lights
work sort of like regular MH light does: the arc tube is heated, the metal halides and gasses are heated to give you light. The difference between a regular MH bulb and a CMH bulb, however, is what the arc tube is made out of. Instead of using quartz like other HID’s, these bulbs use a ceramic arc tube that can reach higher temperatures to heat gasses to that nice even light spectrum plants love.
CMH grow light bulb
Growers are moving to CMH’s because of their power per watt. With the ability to reach high temperatures, a 315w CMH light is known to outperform a 400w bulb and even some 600w’s. Double that with a 630w and you’re getting almost as much power as you would with a 1000w MH light. You’ll not only save money lighting your garden with less power, but you’ll also reduce a lot of the heat you were getting with higher wattage HID’s. The most impressive feature a CMH light has is the spectrum of light they give off. While other MH lights give off a more of a blue-ish hue, CMH’s tend to give off a spectrum closer to that of the sun. Their spectrum rates anywhere from 90-92 on the color rendering index, which means the light your plants are getting is closer to the spectrum of the sun (which has a CRI of 100). All that spectrum means you’re also getting a good amount of UV and IR in there compared to standard HID’s. Ceramic lighting isn’t just staying with MH’s. There are CHPS’s coming out that will give you a flowering spectrum closer to the sun, too. So while they maybe a little more expensive than standard grow lights, they’re definitely worth the extra cost.

Which Grow Light is Best for Your Grow Room

Plants and hanging lights in a grow room
Double ended grow lights and CMH’s are good at pumping out lots of power to your plants. So much so that it can be pretty tricky to figure out which one is best for your garden. That’s why we say when it comes to choosing between these two, take these factors into account:
  1. Coverage- CMH’s have few reflector designs, and all of them seem to have a limited spread of light. DE’s on the other hand, have a wide variety of reflectors to give you as little or as much spread as you want. If you want a larger coverage area, consider going with DE’s.
  2. Heat- Replacing your single ended HID’s with DE’s can raise the heat and humidity in your grow room, whereas replacing them with CMH’s is going to help reduce heat and humidity. If heat is an issue in your garden, CMH’s will help bring temps down
  3. Spectrum- CMH’s are great at giving you that high CRI spectrum, but they may need a little help finishing off plants in the flowering stage. DE’s have the same spectrum as normal HID’s just more intense. You may need a supplemental light with CMH’s, so if you’re used to swapping out bulbs instead of using supplemental lighting, consider going with DE’s
  4. Price- They’re both more expensive than regular HID’s, so when it comes to the price debate we’ve got to go with the heat reduction: CMH’s are more expensive than DE’s, but CMH’s don’t generate as much heat as DE’s. If you want to save money initially go with DE’s; but if you want to save money on heat reduction later go with CMH’s



LED’s are certainly a great option when it comes to grow lights and they have come a long way in terms of being able to compete with DE and CMH lights.

Lee Riddering

Neither. LED beats them both.


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Devin Martinez

Great question, Jon! It really depends on what the ballast you purchase is capable of and what it’s compatible with. The Yield Lab line of 600w and 1000w ballasts, for example, are cable of being used on single ended and double ended grow lights. Other ballasts, like a few made from Quantum, are made specifically for double ended or single ended grow lights. So my suggestion is looking up the make and model of the ballast you have and see if it can be used for both DE and single ended lights (if you can’t find it, Hydro Farm should be able to let you know).

Jon Auble

I just bought a hydro farm DE ballast by mistake- will it run a standard he’s bilb?

Devin Martinez

“Hello Michael.

We would love to help you with that! If you were looking to run the <a href="""" target=""_blank"" rel=""noopener nofollow"">600w Double Ended Kit with two wall mounted fans you would be good to go. Although the Double Ended Kits run hotter than your normal kits it would be enough for the 600w kits with 2 output fans."


I have read a few of the articles on your blog , and I like how you talk about which lights are better for someone like me something so detailed like this helps me decide on what i would like to purchase. Thank you for helping me decide today i will be a loyal customer due to the knowledge i learn from this.

Michael L Thompson

If I use a 600 watt DE kits in a bedroom with just two wall mounted fans will it get hot or will the heat dissipate?

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