DON'T DO IT!
I mean... never use 100% of the power you have available to sing. It will turn into "pushed" sound instead of what I like to call "pulled" sound.
Instead of "pushing", imagine pulling your voice, by the word, from above and behind you. If you sing as hard as you can, you will tense muscles and tendons in your neck, shoulders, jaw and tongue- oh, yes- and your larynx! This will limit your vocal range, will make it very hard and effortful to reach for upper notes, will fatigue your voice, and will sound strained, thin and brittle.
Instead, back off the pressure and you will find yourself with more vocal range, tone and pitch control. You'll be able to blend your registers much better. Your voice will less likely suffer from strain and fatigue.
That's because when you back off a bit, you'll be better able to keep your throat open, giving the vibrations from your larynx an open path to the resonation zones in your face, sinuses, nose, throat and trachea. You'll be able to blend your vocal registers so you are not screaming chest voice and then changing to weak head voice.
Here's the bottom line: Vocal volume should come from more resonation, not more pressure through your vocal cords!!!
IMPORTANT: As you back off the power, you should (and can) add PASSION! Meaning, with less strain in your face, neck and shoulders, you can articulate the words and emotions of your song even stronger.
Whether live performance or in the studio: Back off the pressure + add passion, and you'll find that less is truly more!