Here's a good read:

http://boards.cannabis.com/indoor-gr...-progress.html

Quote Originally Posted by rhizome
Daily smoker? Husband/wife/roommate of a daily smoker? You'll want at least a 400w HPS for flower, and a 600 if you share a lot.

Multi-Smokestack household? A 600HPS will probabley keep up, but three Marley-types will want to go to 1 k. If you see yourself scaling up to small commercial, go for the 600- they scale up nicer, IMHO.
I'd say maybe 2 x 600w...(???) Compared to the 1000w, they are easier to cool, much lower electricity bills (from light and fans), and if you get everything else right, they will grow a lot of flame budz. :jointsmile: