Dimming your household lights is a common practice. Many indoor growers look at dimming their grow lights as the same thing. But, this could not be further from the truth. Many growers dim their lights to reduce the amount of heat inside the grow room during various stages of plant growth. Dimming HID grow lights can be done but understand this will change the quality of the light coming from the grow lamp.
Below are examples of what happens to a lamp’s spectral distribution when the lamp is dimmed. You can see how the spectrum changes; it shrinks and portions of it may actually disappear. This change in spectral energy will have a negative effect on the quality of your plant growth. We understand the need to dim your grow lights. But understand you can get better quality plant growth from a 600W lamp running at 100% than you can from a 1000W lamp running at 75%.
NOTE: We never recommend dimming a metal halide grow lamp. The chemistry in a metal halide arc tube will change dramatically and could cause a lamp failure. You will notice a dimmed metal halide grow lamp will look green. If you see this, it is best to turn the system off and begin troubleshooting.