There are a number of ways to determine the cost of a car. Electric cars are a bit different and some care will make the unusual more comfortable.
First there is the MSRP or sticker price. For the Nissan Leaf you can find this on the company website and it is $32,780.(1)
Then there are incentives offered by many individual states in the US. Here is a listing: 2
Next you might have to install a home charging unit. For the Leaf this is has to be installed by an electrician and the cost is listed as around $2000 plus tax and license fees: http://www.facebook.com/nissanleaf?sk=app_10339498918 For some EV this may be cheaper. The charger is not really part of the cost of the vehicle anymore than installing solar panels or building a garage might be but it is part of the of a car.
In every case you pay for the battery when you buy the car, but this cost can be backed out and calculated as an operating cost based upon the warranty period.
Lets say you purchased the Leaf in NJ. There you could have a 32,780 sticker price. At the end of the year you would get $7500 back on your taxes. There is some discussion in congress about making this a direct grant instead. The cost becomes $25,280 In NJ you get a further $4000 state tax incentive and there is a sales tax waiver on the vehicle. We can deduct the $4000 to make the cost of the vehicle $21, 280 and note that if we had to pay the 7% sales tax on the original price of the vehicle this would amount to $2294.60 (more than the cost of the charger.)
The battery for the Leaf can be estimated to cost around $9000. http://electric-vehicles-cars-bikes.blogspot.com/2010/05/nissan-say-leaf-ev-battery-pack-cost.html It has a 100,000 mile or 8 year warranty. This amounts to $ .09 per mile. But if we are going to use this as an operating cost then the cost of the vehicle becomes (21,280 - 9000) $12,280.
The EPA sticker will give us an estimated mileage. http://www.autoblog.com/2010/11/22/nissan-leaf-snags-99-mpg-rating-on-official-epa-sticker/ The important numbers on this sticker are the full charge range of 73 miles and the KW-hrs / 100 miles. The second number then gives us a rate of .34 KW-hr / mile. We can then go to a chart of US electric rates (3) to find that although the national average is $ .112 the average rate in NJ is $ .167 / KW-hr. You can determine this also with your electric bill. The fuel cost / mile then becomes ( .34 x .167 ) $ .057 / mile and when we add this to the battery amortization we get (.057 + .09 ) $ .147 / mile for a total operating cost for an essentially $12,000 car.
How does this compare to a Honda Fit with a gas engine? The base vehicle is around $15,100 - $19,240.(4) It gets 27/33/30 mileage. The average price for gasoline in NJ is $ 3.597 (5) The combined mileage would then cost about ( 3.597 / 30 ) $12 / mile for a car that costs a minimum of [($15,100 - $12,280) + (15,100 x .07) price diff plus tax on the Honda] $3877 more than the EV. You would have to travel ( $3877 / .027 ) 143,592 miles for the cost of the gas car to be as cheap as the electric. And this assumes that gas prices will not rise during that time relative to electric costs.
The Volt is a hybrid. Its operation as an electric vehicle and economy is highly dependent upon the driver plugging it in. In gas only mode it only gets around 36 mpg. This fall there will be other Electric vehicles available. Slightly cheaper will be the Mitsubishi I Miev at a MSRP of $27,990 http://www.plugincars.com/mitsubishi-i-miev While there are many online EV magazines, for specific issues google is a good place to start a search.