If you want to take long trips on electricity, it can cost ~$3000 in batteries to add extra capacity, in case you want to add that into the equation. Adding extra batteries adds extra weight, which reduces your gas mileage. However, if you run mostly on batteries, you can reduce the weight of gas (10 gallons of gas weighs ~60 pounds).

Send comments to kwhmpg (at) paperlined.org. I'm pretty sure the math is correct though.