On 2012-12-31, Orval Fairbairn wrote:
Since you are carrying ALL the energy needed to run, the weight climbs
out of sight (15:1 air:fuel ratio + storage medium).

On a point of pedantry, the mix is not 15:1 oxidiser to fuel. 79% of
the air takes no part in the reaction, so it's more like a 3:1
ratio. Also, petrol (gasoline) engines are at best 30% efficient
at turning the energy released by the fuel into motion (before even
getting to the drive train), electric traction motors are on the order
of 90% efficient at turning electical energy into motion.

While there's a big gap between what battery storage can do (which does
make it impractical for a typical GA aircraft), the gap isn't nearly
as big as you think it is for road vehicles.