Some source suggests hibernate should not use any power, since it copies the memory to the disk and is powered off.
However, from Microsoft's document, they said "Hibernate uses less power than sleep".
And I noticed something called "hybrid sleep", which windows keeps the RAM being powered, also copy it to the disk. So you can qucikly restore from RAM, or restore from disk if the battery is emptied.
I would be super disappointed if I was expecting my laptop to hold the battery after several days of hibernation but find out this hybrid thing used all the juice in the battery and nothing left.