I sure would like to know the answer to that too. I'd like to maybe drop down to 600 watt bulbs (from 1000W) in the middle of summer here as it gets way too hot. I'll just grow less but i'm sure the room would run a lot cooler than it did last summer. I just don't want to get more ballasts. I don't mind buying a few extra bulbs if this would work. If nobody knows, maybe a call to salvania or one of the big lighting companys would be in order. I'm sure they must have people that sit there all day and answer questions like that. I would call tomorrow if I had phone access where I work. I could use my cell phone but its too noisy. Anyone else would be appreciated.