That's true for petrol engines, though. The price fluctuates, though not generally wildly, and I know -for example- that it will cost me $25-$30 to fill up my

That's true for petrol engines, though. The price fluctuates, though not generally wildly, and I know -for example- that it will cost me $25-$30 to fill up my car. I imagine the fluctuations of the electrical grid are no different and likely more stable. It would make sense to charge more during the day when there's a higher load on the grid anyways, and considering the price of Teslas, I am confident the owners can afford it.