Bigger Battery = Bigger Size and More Weight.
It's really that simple.
The 11" air could have had a 7-hour battery too, but it would be .5lbs heavier and another .5" thicker.
The Asus 1005PE has an Atom Processor that uses 1/2 the power of the ULV Core2Duo in the 11" Air. (5.5W vs. 10W).
It also weighs as much as the 13" air, while being 3" smaller in screen size.
It also comes down to walking around with this for 8 hours:
Or this for 5 hours:
It's really that simple.
The 11" air could have had a 7-hour battery too, but it would be .5lbs heavier and another .5" thicker.
The Asus 1005PE has an Atom Processor that uses 1/2 the power of the ULV Core2Duo in the 11" Air. (5.5W vs. 10W).
It also weighs as much as the 13" air, while being 3" smaller in screen size.
It also comes down to walking around with this for 8 hours:
Or this for 5 hours: