Has Dave said, that could be the issue, i must be missing something..
I have a friend who likes to smoke a bit of wacky backy (and it genuinely is a friend, i dont even drink alcohol, let alone smoke weed). After a few years of buying dodgy stuff from dealers, he decided to grow his own. (Only 2 plants). He's using CFL lamps at the moment but wants to go to LED to save on electricty (light and ventilation).
He shown me on the forum that whats advertised as a 900w LED lamp actually uses near 400watts in electric