400+ HP and 0-60 in 2.9 sec is impressive, but I would much rather have less HP, 0-60 in 7 to 8 sec if I could get more range. Is this overdesign??
It's not like high powered (bigger) ICE that you will always consume much more energy no matter how you drive or even at idle. A highe output electrical motor will not consume more energy than a smaller one unless when you drive it hard. The model S P100D actually has about the same mpge as the Leaf at cruising speed. That's one of great advantages of electrical vehicle and Tesla took advantage of it. As bad as they already are an ICE car this big and powerful would get you low teens if not single digit mpg.
In other words put a tiny little motor will not get you any higher range. What matters most is aerodynamic which is the reason why Tesla put a lot of effort in that area.
Well, 7-8 seconds is really slow. Hope Tesla never makes a slow car. Doubt there is much range to gain on that:).
Welcome to the wonderful world of electrical engines! Their efficiencies are above 95% over a very wide range of RPM's and torque. Not so with ICE. To get a powerful car, you need a big engine and that engine will have its highest efficiency at a very narrow range of RPM and torque which makes it very inefficient for "normal" driving. Even then it will be around 25% thermal efficiency at best. And if you get out of that narrow range, the efficiency drops fast and gets to 0% at idle. This is one of the reasons trucks drive the way they do: their engine has its sweet spot for driving a fixed 65 m/h on a flat road. But that makes their engine terribly underdesigned for everything else like acceleration or going up a hill. This is also one the reasons a hybrid gets better fuel efficiency: their ICE engine is underdesigned for the weight of the car but is perfect for highway and city cruising. And when you need more acceleration, the electrical engine kicks in.
With pure electrical cars, you can give them a larger motor with all the fun of a great driving experience but without the loss of efficiency.