MH grow lights are another variation of HID which use a mixture of different metal salts in the arc tube to create blue, green and yellow light, with a little bit of red. They look bluish-white to humans.
Intensity of Metal Halide vs. LED Grow Lights
MH lights are not quite as intense as equal-wattage HPS lights, but they are still much brighter than fluorescent and induction lights. 1W and many 3W LEDs are not as intense as MH lights, but 5W and some lensed 3W LEDs match or beat metal halide lights for intensity.
Spectrum of Metal Halide vs. LED Grow Lights
MH lights produce a fair amount of the blue light, but little of the red light plants crave. They tend to work well for plants in vegetative growth stages, but don’t perform as well for flowering or fruiting plants. Over 50% of the light created by metal halide bulbs is in green and yellow colors, which plants aren’t efficient at using.
Metal halide does produce some UV light, which helps increase the quality of plants grown under it.
LED grow lights with plant-optimized spectrums including UV can provide all the benefits of the blue and UV light metal halide fixtures create, as well as the red light needed for good flowering and fruiting that MH bulbs lack.
Lifespan of Metal Halide vs. LED Grow Lights
MH lights don’t have a very long useful life and need to be replaced about twice as often, every 3 months to 1 year maximum. Properly-designed, well-cooled LED grow lights will last 5 to 40+ times as long!
Because MH bulbs contain toxic mercury, they cause environmental contamination whenever they are disposed of at the end of their life.
Efficiency of Metal Halide vs. LED Grow Lights
MH lights are more efficient at creating light than fluorescent and induction lights, but are less efficient than HPS and much less efficient than LEDs. When factoring in the spectral efficiency LED grow lights can offer, metal halides are significantly less efficient.