Quote Originally Posted by Nochowderforyou
I'm not too sure about a 400W bulb, but if you're going to be running that much light, you will need some sort of fan or cooling system as they do get very hot.

I just run a small 150hps here, and it costs me maybe $10 extra a month. So with a 400hps with some fans, about $40 extra a month, maybe less. Not a huge noticeable diff., so it's nothing to worry over.
You could easily compensate for a 150watt light. That's only 2-3 normal light bulbs depending on what watt you use for your regular lamps etc...All you have to do is conserve. 150 watt light shouldn't raise your light bill at all if you things right.