Suppose that technological issues have been solved, plug in electric cars are available on the market, and everybody charges his car when he gets home in the evening.
How much would it be your electric bill then?
On average, every electric car would cost about $1.25 per day.
Let's see why.
To get to this result, consider the amount of gasoline that US uses in one day: 380 millions of gallons (pretty impressive!).
As there are 254 millions of cars, it's about 1.5 gallon per car, per day.
Gasoline has an energy content of 121 MJoule per gallon.
Therefore each car use 181.5 MJ per day.
Suppose that internal combustion engine has an efficiency of 15%, while electric cars can go up to 60% (including losses in the charging/discharging of batteries). Therefore an electric car would need about 45 MJ per day.
That is 12.5 KWh per day.
At an average cost of electrical energy of 10 cents per KWh, we get $1.25 per day.