It's non-zero, but not much.
Unless you have some fairly esoteric needs (i.e., keeping the device on a single page for a large amount of time (think sheet music)), and provided you use it regularly, the defaults should be pretty sane (i.e., auto-suspend after a while (like, 15 or 30 min of inactivity), and auto-poweroff never).
If you do need to keep your device inactive for a while (say, in storage for > 2 weeks), then you might consider powering it off.
Other than that, you might have been restarting a holy war on the subject of sleep vs. poweroff
.