Business Insider published an interview today with Tesla founder Elon Musk in which Musk makes a striking claim: “You have enough electricity to power all the cars in the country if you stop refining gasoline,” he asserts. “You take an average of 5 kilowatt hours to refine [one gallon of] gasoline, something like the [Tesla] Model S can go 20 miles on 5 kilowatt hours.”
The math behind the claim is simple. Refinery efficiency is about 90 percent and the energy content of a gallon of gasoline is about 132,000 Btu. Put that together and you have about 13,000 Btu of energy cost per gallon of gasoline produced, which is equivalent in energy terms to 4 kilowatt hours. (The 6 kilowatt hour claim is based on outdated efficiency figures.)
But this is flawed in two big ways. The first is that most of the energy used by refineries doesn’t come from electricity; only about 15 percent of it does. That cuts the electricity-used figure down to about 0.6 kilowatt hours. The second is that conversion of fuel to electricity is pretty inefficient. A process loss of energy equivalent to 0.6 kilowatt hours translates to an actual electricity loss of around 0.2 kilowatt hours.
This is consistent with refinery data. The Department of Energy estimates that refiners used 47 TWh of electricity in 2001 to produce refined products from 5.3 billion barrels of oil. Assuming that you get 42 gallons of refined products from each barrel of oil, this works out to about 0.2 kilowatt hours of electricity used for each gallon of gasoline produced.