Electric flight in the history of flight has never been “impossible.” Anyone who told you it was impossible didn’t have the capacity/desire to think in terms of fundamentals beyond existing rules of thumb. (“Existing technology” is a nice weasel term, but we’ve had electric flight of various types demonstrated decades ago.)

30% is not high. It might convince you to do some drag reduction on your aircraft to compensate. Most small general aviation aircraft are terribly aerodynamically inefficient even compared to state of the art aircraft 50 years ago. 30% is barely relevant for the short intracity trips in this article.