The best answer is not to dim, but to get a ballast that is switchable...say a 400-600-1000 or just a 600-1000= much better than dimming...just don't use a 400watt bulb on 600 or 1000
As for where the power went? it never got used...say you have a garden hose and it produces 5 gl a min...
Dude! DON'T DO IT!!! they arn't anywhere near ready yet you still have around 5-6 weeks to go yet...not only will you get a much larger harvest by waiting, but a better quality herb as well...just chill a bit.