600w ballest

will a 600w ballest with a 400w bulb still use 600w of power
cheers

no and you will blow the system...

Not, but I hear if it's a certain type of ballast it will support both 600 and 400. Same with some 1000 watt ballasts, you can use 1000, 600, or 400 watt.
Just check what kind of ballast you have and do some research.

Edit:
And even if you put a 400 watt bulb in a 600 watt ballast, it will still only be a 400 watt bulb, the ballast isn't going to push it to 600.

it can work for a short time, but ultimately it will blow the bulb