There was another thread about this somewhere...
The consensus was - yeah, it drains more then 1A with cell + wifi + cpu maxed + display. How much that drains your device depends on the charger in use, battery, etc.
Suggestions:
1) start with a full battery
2) turn off display when using
3) plug it into something! The OEM charger is 1A, most USB charges are only .5A
You *should* be able to get close to break even on a 1A charger... something like 300-400ma drain, which on an OEM battery is about 4-5 hours
(that would be 2-3 hours on a .5A USB port, or 1-1.5 hours on battery
)