The U.S. Department of Energy has just released an interesting online tool that allows you to see what the amount of electricity necessary to drive an average electric car as far as a gallon of gasoline would cost where you live. They call this the 'eGallon', and the U.S. average is $1.14. It goes as low as $0.83 in North-Dakota and as high as $3.69 in Hawaii where electricity is most expensive (but then, if you live there you should get some solar panels!).
It doesn't tell the whole story...As you can see in the chart above, the cost of electricity is a lot more stable than the cost of gasoline. That predictability is a real benefit (especially if there's a war in the Middle-East or something like that), but there are others. In a lot of places, you have time-of-use electricity rates, and areas that don't have dynamic pricing yet will almost certainly get it over time (it simply makes sense -- it costs more to produce electricity at peak time than in the middle of the night). Plug-in vehicles are mostly charged at night when time-of-use rates can be way lower than they are during the day and during peak time. In some places, they go down by 50%. This means that the Department of Energy's eGallon prices are too high in many places right now, and almost everywhere over time.
On top of that, free ways to charge are popping up all over. For example, Tesla's Supercharger network is free to use for Tesla customers. That should put pressure on other plug-in makers to create their own free networks, or to at least provide access to third party networks when you buy one of their plug-ins. There are also workplaces and stores that give free access to charging stations, a perk that should become more common in the future.
So while the average eGallon price of $1.14 might technically be correct based on average electricity prices and EV energy-efficiency, that doesn't mean that it's what you would pay. If you have time-of-use electricity rates and charge at night and sometimes charge at free stations, your real-world cost could be significantly lower.
A few words on the economics of electric carsThis has been bugging me for years. For some reason, most auto journalists can't seem to stop boiling everything EV-related down to "How much does it cost compared to a gasoline-powered car? Will you save money?". Don't get me wrong, it's a valid question to ask and it's good to have the info available. But it's just one element out of many, and it shouldn't overshadow everything else...
When it comes to picking a vehicle, most people won't go straight for the cheapest, most bare-bone model they can find. The ultimate goal is not to "save money". They'll spend more on certain brands, or on accessories and performance options (fancy wheels, comfy seats, bigger stereos, sunroofs, bigger engines, etc). Some of these choices bring performance or comfort improvements, others are purely about aesthetics, and some are harder to pinpoint... Bottom line, there are all kinds of reasons for picking one vehicle over another, and these can certainly include environmental reasons, technological ones (early adopters wanting to be first to ride this wave), or psychological ones (on top of the other benefits, many find it more pleasurable to drive plug-in vehicles than gas ones).
I wish the auto press - mostly composed of gearheads dreaming of Bugatti Veyrons - would stop with the double standard of judging plug-ins only on whether or not they'll save you money, because after it's been repeated thousands of times, the general public starts to think like that too. It's okay to pay more to not burn gasoline. That's a real benefit worth paying for (more than fancy wheels, in my opinion), and it would be worth even more if we put a reasonable price on carbon emissions.