An old XKCD what if: https://what-if.xkcd.com/128/
> What in my pocket actually contains more energy, my Zippo or my smartphone? What would be the best way of getting the energy from one to the other? And since I am already feeling like Bilbo in this one, is there anything else in my pocket that would have unexpected amounts of stored energy?
Which in part had:
> A container of butane the size of a phone battery could, in principle, power the phone about 13 times longer than the battery itself could. The obvious question, then, is "why doesn't my phone run on propane?"
...
Also http://www.jefflewis.net/blog/2012/01/how_much_gas_to_charge...
And while that's based on a study from Exon (no longer accessible)... but the math part is math no matter who does the math.
> So, the claim that there's enough energy in a gallon of gas to charge an iPhone every day for 20 years seems pretty reasonable (in reality, when you look at the efficiencies, you won't be able to put all that energy into charging the phone).
> An iPhone may not be huge, but 20 years is a pretty long time. It really just goes to show how much energy gasoline contains, and why it's so useful for powering vehicles.