As for efficiency, in the worst case, a coal-fired power plant is about 1.75 times as efficient as aninternal combustion engine in extracting the energy from its fuel. It is estimated that around 6% of the power they generate is lost to such things as voltage drop. An electric car such as the Tesla isaround 90% efficient in transforming that electrical energy into forward motion.
So even with the Lord Voldemort of electrical generators, an electric car has a huge advantage (about 50% better) over atypical internal combustion engine, which struggles to squeeze out 20% of the energy from a gallon of fuel, blowing the rest out the exhaust as noise.
If the energy comes from a renewable resource(say solar powered recharging stations for exchangeable batteries), the advantage just multiplies.
The issue for electrics is that most people can't get out of the habit of thinking that they needone car to do everything. So while a battery-powered electric is a viable solution for a commuter car, it can't get them from LA to San Francisco on a single "tank" of electrons.
A Tesla (a carthat goes from 0-60 in under 4 seconds and leaves a $400,000 Lamborghini sucking air in a high gear roll-on) can make a round trip from Santa Monica to Santa Barbara on a charge, but that's about thelimit. If they could get recharge times into the range it takes to fill a gas tank, they'd have it solved.
Unless there are battery exchange stations as common as gas stations, the problem will beamps.
Recharge times have been improved to as little as 10 minutes for lithium iron phosphate laptop batteries through a process discovered at MIT.
When that technology reaches commercial...