Sometimes also called Light Emitting Ceramic (LEC), these are a variation of metal halide (MH) lights which use a ceramic arc tube. This allows higher temperatures and better stability, which creates a more-even coverage of the light spectrum than regular MH lights. Because the ceramic tube can get over 1700 degrees Fahrenheit (920 degrees Celsius) it is difficult to make CMH lights in high wattage versions, so the largest bulbs typically run 300-400 watts.
Intensity of CDM / CMH vs. LED Grow Lights
Like all HID lights, ceramic metal halide lights are fairly bright and are certainly more intense than 1W or un-lensed 3W LEDs. 5W and some lensed 3W LEDs can be at least as intense as CMH.
Spectrum of Ceramic Metal Halide vs. LED Grow Lights
CMH lights have the best overall plant-growing spectrum of any HID light, with blue and red and even some UV light. However, almost 40% of the light they create is green and yellow light plants cannot use efficiently. LEDs allow grow lights to be fine-tuned spectrally to more efficiently grow plants.
Lifespan of CMH vs. LED Grow Lights
Ceramic metal halide lights have a longer lifespan than normal MH lights, but still need to be replaced every 6-12 months. As with all HID grow lights, they contain mercury which poses a health risk and contaminates the environment when they are disposed of.
LED grow lights last many times longer and contain no toxic mercury!
Efficiency of CMH vs. LED Grow Lights
Ceramic metal halide lights aren’t as efficient at creating light as HPS, but they are more efficient at creating the colors of light plants want, making them more efficient grow lights than high pressure sodium. LEDs are more efficient at creating light than CMH, and when properly designed, LED grow lights are still much more efficient at growing plants than ceramic metal halide.