How do you get electric costing $10?
First, Tesla gets 250 MPC for the 85 KWH pack. Assuming that you fully charge it, it will be around 100KWH to do so (efficiency losts).
So, here in America, nighttime electric costs is around .06 / kwh. As such, this is less than $6 to go 250 Miles.
Now, gas costs 2/gal today but will go up. However, that means that you pay $25/for the 250 miles. However, note that it does not include oil, gas car maintenance, etc. So, that is minor, however, over 2 years, and at least 25,000 miles, the electricity will be 600, while the gas will be 2500. Starts to add up and that was with gas at 2/gas. Within a year, we will be back to 3 or 4. At that point, gas for the 2 years, will be 3800-5000, which is quite the uptick vs. the 600.
Finally, coal is currently 36% of America's electricity. Due to W's mercury regulations, coal will be below 33, probably 30% by 2018. Now, add on the push to drop emissions, esp. CO2, and I think that we will see coal be less than 25% of America's electricity by 2020.