If half of American commuters switched to EVs, the daily energy demand on the grid would only increase by 10-15%. The difference between peak load and average load is close to 30%, so we could handle that new EV load with the existing generation capacity. We just need market solutions to incentivize owners to charge during off peak hours, which most utilities already have via time-of-use rates and EV-specific plans.
To be more clear: the US grid with its existing generation capacity could certainly handle 41% of consumers switching to EVs. We would simply not ramp down as many power plants at night as we do now [1].
However, that would result in this additional marginal demand being satisfied mostly by fossil fuel plants: natural gas and coal, which currently ramp up and down on a daily basis. What is more likely to occur is that the new marginal demand caused by EVs will be satisfied by new capacity from solar and wind farms. Areas with good solar capacity (CA, FL, the southwest) will incentivize EVs to charge during the day, and areas with more consistent wind capacity (the midwest) will incentivize charging at night. Coal plants will increasingly close for economic reasons, while existing natural gas plants will continue to run at lower capacity factors.
Depending on how electricity and carbon markets are structured, and how the costs of different generation technologies and fuels change in the future, there's a good chance that the US grid of the future will look like how I described, and that people will pay less of their income on energy services, and that the air in cities and homes will be cleaner, and that people around the world will be less at risk from the effects of climate change.
