Well, to begin with, you are off by a factor of 3 on useable energy, and perhaps by a factor of 2 on the energy density of best batteries of today (Wikipedia st

Well, to begin with, you are off by a factor of 3 on useable energy, and perhaps by a factor of 2 on the energy density of best batteries of today (Wikipedia stated 0.95 MJ/KG for best Li batteries), so achievable range should be ~380 km to begin with. I'll also note that the fuel tank itself has weight (though I do not know how much it is). Next, the Stationair is a really old airplane, the basic design is over 50 years old. If we take the 2004-ish Cessna 400 instead, which has a 60% greater maximum range than the Stationair... perhaps we can claim that 500km+ is achievable, without calling upon radical new designs or further technology improvements. And an airplane with ~500 km range is pretty sensible. (frankly, long trips in small planes are a bit of a trial, though probably less so in a smooth and quiet electric plane). OTOH, you do need to consider reserve range, that does not work in favour of electrically powered aircraft. But the effect might be limited to having to add some battery capacity, sacrificing some performance along the way. In conclusion... It does not even matter if the first commercially available electric airplane matches the petrol airplane on range. It would be nice to have a useable range, but ~500 km is enough for many applications. The electric airplane does not need to dominate the market from the start... just enter it.