Depends on how you grow as much as anyting else.

A 1000w light they say is good to cover 4' x 4' area but I say it is only really good for a 3' x 3' area. How you grow with in that area is up to you. If you have clones then you and do a SOG grow or a SCROG grow but if it's from seed then that does not work.

4 works and even 6 will work but pushing it. They would all need to be turned everyday anyway if you grow from seed.