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That means they are only a battery capacity factor of 2-4 away from range parity.

If you only care about range, then my 6-cylinder 2007 RAV4 has an estimated 300 miles average range, and the beefiest Tesla Model X has a 289 mile average range, so we're already roughly at parity as far as I'm concerned.

BTW, the efficiency numbers for gasoline engines get even worse when you factor in the supply chain. For every gallon of gasoline refined, it takes about 6 kWh of power to refine, plus a lot of fossil fuel power to extract and transport. That same amount of energy input would get an electric car almost half as far as the gallon of gasoline would, even before you factor in the energy in the gasoline. So your overall efficiency is likely to be more on the order of 20%.

Of course, you're moving around more weight with the EV, because they don't get lighter as they discharge, and their specific power (energy per unit weight) is only about 1/50th that of gasoline. When full, that 14-gallon tank of gasoline weighs ~87 pounds plus whatever the plastic tank weighs (15-20 pounds, typically). So assuming you get it near empty every time, it weighs on average about 44 pounds plus 15-ish. Let's call that 60 pounds.

The Tesla pack weighs 1200 pounds. And the rest of the Model X weighs about 500 pounds more than the RAV4 in question, for a total difference of a whopping 1700 pounds. If the ICE-based car weighs only 68% as much as the electric, then instead of being ~5x as efficient, the EVs are only ~3.4x as efficient. Of course, this discounts the efficiency/inefficiency of producing electricity, but that's hard to quantify.

And what of it?

Coal fired plants are typically around 33% efficient - meaning that one third of the energy they release as heat is converted into mechanical (and hence into electrical - that conversion is nearly 100% efficient) energy. In comparison, an internal combustion engine - as used in a petrol-driven vehicle - gets around 20% efficiency. That gives a bit of room for electric cars to potentially emit less carbon dioxide than a petrol driven vehicle, even allowing for the greater carbon efficiency of hydrocarbons compared with coal.

Here's a nice little chart, showing you the carbon dioxide emitted per kWh of electricity produced. Let's take lignite: 2.17 pounds (about 1kg) of carbon dioxide for each kWh produced.

Now. The Tesla Model S has a range of 557km (90 kWh), 480km (75 kWh) or 400km (60 kWh). Let's take the 557km option (which gives the worst case figure). That's 6.189km per kWh, or about 162 grams of carbon dioxide of emissions - using worst case carbon generation - per km travelled.

One specific model that is sometimes cited as equivalent to the Model S is the Mercedes S-class. This, based upon Mercedes' own figures, has CO2 emissions ranging from 118g to 239g carbon dioxide per km. So best case, with a diesel S-class vehicle, you're about one third better than the Model S; worst case (5+ litre petrol engine), you're 50% worse. And this is assuming that the owner of the Model S isn't paying a premium for renewable energy, and/or doesn't have solar panels on the roof, and that the electricity generation in the area is all coal-based.

But. Another factor to consider as well is the cost of transporting the fuel: trucks have to carry that fuel (diesel, petrol, etc.) to the station, and you have to drive to the station to refuel. An electric car? The infrastructure is already in place; there is negligible marginal cost in getting the power from the plant to the car. Also the energy required to refine crude oil into usable fuel is not insignificant - the equivalent of 6 kWh of electricity is lost for each gallon of gasoline refined. That effectively adds 6 kWh per km to the S-class diesel, automatically putting it in the "worse than the Model S" class!

Then, too, converting a centralised power plant from coal to something greener (gas, geothermal, nuclear) is a lot easier than converting millions of privately owned vehicles.

In other words: even allowing for greater use of coal fired plants, electric cars are still a net carbon dioxide win, thanks to greater efficiency in the energy generation and transportation process (end to end).

If you're going to compare end-to-end CO2 emissions - which is fair enough - you also need to account for the energy required to refine petroleum, and to transport it to the service station (where the car is filled up). A quick Google search suggests that one gallon of gasoline requires the equivalent of around 6 kWh of energy to be produced. If failing to take that into account means that ICEs are about as efficient as electric cars powered by coal-fired electricity, then electric cars represent a net win from the carbon dioxide and energy usage perspective.

It gets more complicated if you look at the energy required to produce the vehicle, of course, but over the expected lifespan of a vehicle (10 years or more), I'd say that electric vehicles are most likely a net win, even if the electricity is produced by coal-fired plants.

thirdly, it takes about 6KW at the refinery to make a gallon of gas, and most electric vehicles can go further on 6KW than a gasoline powered car can go on a gallon of gas. So getting rid of the middleman conversion to gasoline actually reduces energy consumption. http://gatewayev.org/how-much-...

It takes 6 kWh of energy just to REFINE one gallon of gasoline from oil. A reasonably efficient EV can go 15 to 20 miles on that amount of electricity alone. And that's before you ship the gasoline to the station, pump it into the car and burn it.

The vast majority of EV charging occurs between midnight and 4am, when there is ample capacity, esp from wind, so EVs actually use the cleanest part of the grid.
Which in California is quite clean to start with: most of its electricity is coming from carbon-neutral sources (hydro, nuclear, geothermal, wind...); only 7% was coal in 2010 and getting lower.

Another sobering thought: the energy spent refining gasoline alone (6kW*h / gallon) for a 20-some mpg vehicle would be enough to propel an EV the same distance.

For a true apples-to-apples comparison, we should include the considerable CO2 emissions that come with refining and shipping petrol.

Indeed.
In the US, according to the DOE, refining 1 gallon of gas uses about 6 kW*h. This is enough to propel your typical EV (e.g. Nissan Leaf or Mitsubishi i-MiEV) some 30+ km (20 mi), significantly more if you hypermile.
So there you have it: an efficient EV can travel the same distance as a gas-guzzler on just the energy needed to refine gasoline.

The amount of electricity required to travel a certain distance with an EV is roughly the same as the amount of electricity used to refine the gas for a regular vehicle that travels the same distance. According to DOE: http://gatewayev.org/how-much-electricity-is-used-refine-a-gallon-of-gasoline

Fascinating link.

Alas, it's carefully overlooking a few key details.

One of which is that the energy of crude oil is in no way related to the electricity required to refine said crude oil.

What they're actually making a guesstimate to is the amount of electricity that could have been generated INSTEAD of making the gasoline.

And they're overestimating that by assuming that the making of electricity is 100% efficient.

Which it's not, in case you were curious.

The amount of electricity required to travel a certain distance with an EV is roughly the same as the amount of electricity used to refine the gas for a regular vehicle that travels the same distance. According to DOE:
http://gatewayev.org/how-much-electricity-is-used-refine-a-gallon-of-gasoline