I bet it makes the bulb last longer too?20/4 ONLY to save a bit on the bill. For the last 10 years my light only went off a few times a year when I had to replace the bulb or move the light. Otherwise 24/0. 600hps
Everyone who can especially with autos should try 24/0 unless temps are an issue and you'll see the difference in grow speed vs 6 whole hours less per day.