While we're considering the possibility that oil could decline further, I'd like to share something on the infrastructural cost of gasoline. Acxording to the EIA (
Factors Affecting Gasoline Prices - Energy Explained, Your Guide To Understanding Energy - Energy Information Administration) in 2013 the average retail price of gasoline in the US was $3.51/gallon. 68% of this was due to the price of crude oil which obviously varies with the oil market. However, refining, retailing and taxes accounted for 9%, 11% and 12% respectively, and these costs do not substantially vary with the price of oil. These are the infrastructural costs of gasoline that consumers pay for the convince of filling up at the gas station of their choice. This infrastructure cost is about $1.12/gal. So even if crude where were free and delivered to refineries at no cost, the retail price of gasoline would still be about $1.12/gal.
Given a price of electricity at $.12/kWh, average EV efficiency of 3.5 mile/kWh and average gas vehicle efficiency 22.5 mpg, EVs reach fuel cost parity with gasoline at about $0.77/gal.
Thus, EV parity gas prices are well below the infrastructural cost of gasoline. EVs will always be cheaper to power than gas vehicles no matter how low the price of oil may go.
As a handy little model for gas prices, it is convenient to remember that there are 42 gallons to the barrel. So roughly we get:
Gas ~ 1.12 + Crude/42
So even with oil as low as $10/bbl, gas will be about $1.36/gal.
So the average family is spending about $500 to $600 per year per vehicle just for the convenience of gasoline infrastructure. EV infrastructure is much lower, so in the long run EV infrastructure wins regardless the price of oil.