Are you quite sure it is hibernating, not in Standby or Sleep? Both of these consume power, the latter to keep the RAM active.
Hibernate is supposed to be the lowest power drain, where the contents of RAM are written out to disk (hiberfil.sys), and the PC powered off.
That's generic Windows / laptop behaviour, I don't know the eee devices, so I can't say how well they implement power save modes, but it does sound a bit low to me.
SD