How do you determine how much sleep you need each night? Some nights I am energized with 7 while others 8 1/2 and on and on. It just isn’t consistent

Try the different amounts of sleep yourself, and see how you feel. If you still feel tired after 8 hours of sleep, it could be that your quality of sleep isn’t as good as you want it to be. One thing which helps with this, is balanced nutrition.
Sincerely and respectfully,
Selmaan A Ali