The only things that should use any power when in hibernation are the most basic motherboard functions - basically, little more than supplying enough power for the PC to monitor the power button so you can turn it on - though there could possibly be other small things such as wake-on-LAN that remain on during hibernation, though it doesn't seem very likely, but you could check those in your BIOS. In short, when a computer is in hibernation, it should be just the same as if you did a normal shutdown instead of hibernation.