It gets trickier, though, if the added demand all comes from one neighbourhood, or at the same time of day.
Electricity demand is low late at night, and often dips around noon on weekdays. But the power grid tends to heave a bit in the evening as people arrive home from work and turn on lights, ovens and TVs.
And what if an entire street of residents bought electric cars and plugged them in to charge at the same time?

I honestly consider this a good problem to have, and easily solvable at that considering we can be using batteries to store our power that can be charged at anytime and then use the battery storage to charge a car as needed. That and a ton of advancements in the next 4-5 years will change things drastically, we always think linear, but what we should be thinking is exponential. Five years of advancements today is what 50 years of advancements was 50 years ago.