If you are talking about pure electrical cost, the average cost per kwh in the US is about 12 cents according to NPR.

An average Nissan Leaf battery is about 24kwh (although some cars have much smaller or larger batteries). So if you assume an average Leaf is totally empty, and charging to completely full, that would be a little less than $3 of electricity for roughly 84 miles of range.

To charge a car quickly takes a lot of electricity. But to trickle charge a car takes very little electricity. You can charge cars on as little as 120 volts at 8 amps -- that's less electricity than the average plug-in space heater.

A small parking lot could easily handle 20+ cars simultaneously charging overnight, with just a single standard US household circuit. (100 - 150 amps).

That's interesting, thanks.

But why didn't you consider other costs, such as equipment installation and maintenance?

And what about the grid? Can the grid sustain the equivalent amount of energy that the nation's cars burn every day in gasoline?

It costs $1 to put 8kW (30miles) into a car, and takes about an hour (for a level 2 charger) so the cost of electricity is less than the land value (unsubsidized meter rate) of the parking space itself, in any urban area.

Why didn't you consider other costs, such as equipment, installation, maintenance, etc? Why did you reduce the value to the parking meter rate?