you're wasting more electricity by shutting it off.
The ibook uses less power than a digital clock when asleep, which is far less than the gulps of power required to shut down and reboot the computer once. Plus saves time. Waking from sleep is a lot faster than booting.
MacBook Pro - M2, Ventura 13.6 Safari Tech Prev 17.0 Safari 16.6 Firefox 116.0.2 iPhone 7 Version 15.8