here is my quick analysis.
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US electrical capacity, one million megawatts.
average load factor is 50%, so I guess that nightime load
factor is 20% or so.
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average electric car gets 4 miles per kilowatt-hour.
suppose average daily-drive is 40 miles, and charge time
is ten hours, demand is 1 kilowatt per car.
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100 million times 1 kilowatt, is 100 thousand megawatts,
or 10 percent of the capacity.
Nighttime load is more like 60% of what is spinning, not 20%.
Here are a couple of typical load profiles found online.
http://esm.versar.com/pprp/factbook/stateneed.htm
http://www.dpe.gov.za/images/Eskom_4.gif
Many power-intensive industries actually ramp up operations at night to take advantage of lower power costs. This tends to flatten the demand curve.
The other big fallacy is that there is no easy way, in most utilities, to ensure charging only happens at night during off-peak times. This is a HUGE issue for utilities. When you start affecting system peaks, even just a little, there is an enormously expensive capital cost for additional generation, transmission, and distribution.
This would have to be overcome for your scenario to be workable.
It’s also worth mentioning that an EV that runs at your level of power consumption is a much less capable vehicle than what most people are used to currently, especially in this country. So there would be a huge acceptance issue, and/or the power requirements would go up dramatically, perhaps as much as 2X.
Like most things, the devil is in the details. I’m not saying it’s not do-able, but it’s not as easy a thing as you seem to be assuming.
