We’d need a huge number of new power plants
If all 245 million cars were electric and driven an average of 20,000 km per year, we’d need 1,078 TwH (980 TWh or 980,000,000 MWh plus 10% more to account for battery self-discharge) requiring 4,325 Twh of US electricity production (in 2013 the total generation of electricity in the United States was 4,058 Twh). This doesn’t include transmission losses and the likelihood batteries won’t live up to their full life span from heat, cold, and rising cost of rare earth metals. And in 2014, 39% of electricity came from coal.
Do electric cars really save much energy? NO.
4.4 MWh electricity needed per electric car per year
The PRIMARY energy needed to make this electricity:
60% efficiency loss of generation process (average for US coal and natural gas generation)
10% Electricity transmission losses
12.2 MWh of primary energy required per car
44,000 Megajoules of energy per electric car per year (3,600 MJ-1 MWh)
2.2 Megajoules per car per year per km driven
15.9 km/liter for electric car when the primary energy, coal or gas used to generate electricity, is expressed in gasoline equivalents (35 MJ = 1 L)
37.4 Primary energy requirement of electric car, expressed in miles per gallon.
Implication: The primary energy required to power electric cars is not that different from high mpg gasoline cars, which exist already. Depending on how electricity is generated, there could be some emissions benefits (but not if coal is the primary source of electricity, as it is now, and will be even more so in the future as fracking suddenly peaks and natural gas production drops off a cliff). Some benefits could also be obtained through a high mileage fleet, perhaps less of an undertaking than switching to electric cars.
J.P. Morgan. November 21, 2011. The quixotic search for energy solutions. Eye on the Market.