Ironically it is going to be easiest for places with the cleanest power (hydro, nuclear, geothermal, wind) because clean power tends to be non-burstable while fossil fuels are.

So in places like France or Ontario what will happen is that the cars will automatically charge when rates are low (at night) and may even help the grid by acting as remote batteries. For example, you could keep your car at a 70% minimum charge as a configuration then allow the power grid to pull from you as needed. This would passively reduce your overall power bill as you're selling at peak demand and buying at peak supply.