if you want max yield from 16 plants in one harvest than i suggest 9000watts HPS in a 20'x20' room with 12 foot ceilings and a dedicated cooling system.be prepared to spend 1000's of dollars on equipment/supplies/electricity. expect a harvest of at least 16 pounds and be prepared for criminals with guns to kick your door in and take it all away. seriously.... PLEASE start smaller per Rusty's advice as it sounds like you have little experience at growing indoors.