If you have a dimmable 600/750/1000 watt MH / HPS, when do you change wattage?

Does it matter if heat is not an issue?

I have the Vivosun dimmable ballast that switches from 600 to 750 to 1000 watts and takes a metal halide and HPS bulb.

After I ran the 6" inline fan that kicks on due to temperature into the attic there were no heat issues, it’s winter, but I have 55 F to 79 F temperature range per day.

This is my first grow with this light, so I used the MH at 600 at first, then did 600 HPS, 750 HPS and then 1000 HPS. I think I just wasn’t sure about light intensity burn.

So could I have started with 1000 watts or is that going overboard? Electric bill wise doesn’t matter, it only changed by $20-$30/month.

Graph below is my current grow, the photo below is from today.



Im no help but that is a good question ima tag along

1 Like

Guess no one knows. I did 600 for vegetative, then 750 when I started flowering, then up to 1000 about 3 weeks into flowering. No light burn happened, ducting into the attic causes no heat issues as long as the light is 16"+ from the tallest part of any plant.

1 Like

wow. that’s some hot watts. Great looking girls!


First time using this light, and it’s the best looking grow I’ve ever had after about 10 grows total. Hopefully it works out in the end.


Congrats. you must be doing it right.

As long as you have the co2 in the room, 1000 watts is good. I ran mine at 75% and produced some nice plants for years, but I had heat issues.