Essentially dirty methods of producing electricity and converting that electricity back into mechanical energy are less efficient than gasoline engines. So yes - we do need electric cars and it's great companies are making them but that won't have a significant impact until the industrial-scale energy problems are addressed.
Small gasoline engines are pretty damned inefficient, and I think it's only reasonable to compare full lifecycle costs of our energy sources. For coal, that includes mining. For gasoline, that includes refining (and military defense of oil?). For all, it includes transportation, etc.
It's not obvious to me that gasoline is more efficient than electric. (Nor is it obvious to me that the converse is true, either.)
In countries that have electricity coming from fossil fuels, it's inherently less efficient. In countries like Norway where everything mostly comes from hydro power, this is completely different.
http://www.eia.gov/electricity/annual/html/epa_08_02.html
That's slightly better than the typical maximum efficiency of an internal combustion gasoline engine (and way better than the average, including idling and other inefficient operating conditions).
Electric cars suffer from two additional conversions, each of which adds inefficiency, but it's not obvious to me that this overcomes the efficiency benefit from having a central power plant using fossil fuels more efficiently than in the auto. To me, it seems close enough that it takes actual analysis to determine the winner.
They are also definitely cleaner for local environments - it is easier to regulate emissions from a couple dozen central powerplants then millions of individual engines.
"Inherently" less efficient? As in, "electric cars are inherently less efficient that gasoline cars in fossil-fuel countries?" What a claim! And untrue! Unless you meant "electric cars in fossil-fuel regions are less efficient than electric cars in nuclear regions" then sure. But that's obvious.
Even in India, which has the worst carbon emissions coming from coal in the world, electric cars are about on par with gasoline ICEs. In India, it costs about 350 grams of CO2 emissions per kilometer of EV travel. That's roughly equivalent to a 25-30 MPG gasoline vehicle when you look at well-to-wheel for both.
In every other country in the world, coal emissions are better, which means that categorically electric vehicles are better for emissions than gasoline vehicles, even if the power source is coal.
Source: was a hybrid vehicle powertrain engineer.
In America; and really, most of the wealthy bits of the world, this is purely a political choice. fission is a real answer that we can use right now, one that pretty provably kills fewer people than coal. But coal kills people very slowly in a way that isn't very dramatic, while when a nuclear problem gets that bad, it's very scary and dramatic.
We burn coal for the same reason that we heavily regulate airlines, while we let just about any yahoo drive just about any car, no matter how unsafe.
But, the point about electric cars is just that if the left actually starts to believe in global warming like they say they do, and actually decides to solve the problem, like they say they want to, rather than just opposing cheap energy on the principle of "you shouldn't waste things" (e.g. "I can afford less mature energy sources, so why shouldn't you?") - the technology of fission is there, and building more nuclear power plants is only half the solution, the other half is converting our transportation network to run on electricity rather than oil.
I mean, yeah. For now? electric cars are largely signs of wealth that rich people can buy. But the point is that having the technology out there, working with it, improving it, gets us more ready for the day that we do decide to get serious about our energy problems.
Only on very new generation plants (for coal national average is cited as 32% - it may be slightly higher now)[1]. A 2016 Toyota Prius is advertised as being at 40%[2]. I remember reading a 70% ballpark for Tesla's but it might have gotten better (I can't seem to find the article now).
[1] https://www.fas.org/sgp/crs/misc/R43343.pdf
[2] http://gas2.org/2015/05/27/2016-toyota-prius-engine-achieves...
I'm not sure how much oil needs to be burned to produce 6 kWh, but since a GGE is 33.4 kWh, I'd assume it's at least 1/6th of a gallon. Gasoline emissions need to account for the oil burned to produce that heat and all energy consumed in the gasoline's storage and distribution.
Coal power emits about two pounds of CO2 per kWh according to this page: http://www.eia.gov/tools/faqs/faq.cfm?id=74&t=11
2lbs/kWh * 0.3kWh/mile = 0.6lbs of CO2 per mile. However, that's before transmission losses and inefficiency in the charger and battery. Transmission is about 94% efficient (from http://www.eia.gov/tools/faqs/faq.cfm?id=105&t=3), charging is about 92% efficient, and the battery is about 90% efficient. That's about 78% efficiency in total, so divide that 0.6lbs by 0.78 to get 0.77lbs of CO2 per mile.
Burning gallon of gasoline emits about 20 pounds of CO2. Dividing by 0.77lbs of CO2 per mile gives us an equivalent of 26MPG, approximately.
Not spectacular, but not bad. The Model S is a big and powerful car, and similar gas cars have similar or worse efficiency. You'd be better off driving a Prius in this contrived situation, but then the "no real-world grid is 100% coal" thing comes in. For example, my local grid is about one-third coal, one-third natural gas, one-third nuclear. That cuts CO2 in about half compared to 100% coal, so now it's more like 52MPG. And coal's share is constantly sliding downwards, so over the lifetime of the car that number will improve.
I don't know as much about other emissions, but I'm confident the coal version will easily be better there. Big power plants are easier to run cleanly (they're easier to monitor, they don't care about weight nor much about space, and there's a single stationary point to install scrubbers, filters, and whatever else) and they tend to be far away from people.
Edit: I forgot to mention losses in the system from before the act of combustion. For a proper accounting, you need to account for emissions for the whole chain, from getting the stuff out of the ground to moving the car. Coal is much more efficient at getting out of the ground and into the combustion chamber, since it's already in burnable form, and then gets shipped in huge bulk by freight train. Efficiency losses there are single-digit percentages. Gasoline needs to be refined which alone takes something like 15% of the energy in the gasoline, plus transportation involves lots of small quantities being trucked all over the place. Total losses are about 20%.
I also want to say that I'm not really defending coal here, and I'd be quite happy if we could just stop burning it entirely. But the reality is that it's there, and it sucks, but even sucking as much as it does, it's still better than burning gas in hundreds of millions of little motors.
Source: I was a hybrid vehicle powertrain engineer.