It may seem something of a departure from the usual iDB content, but just bare with us for a second.
According to Bill Colton, a VP at ExxonMobil, just one gallon of the company's gas has the power to charge an iPhone once per day for a whopping twenty years. That's a lot of charges.
While it is highly unlikely that Apple's next iPhone charger will come with a tank instead of a plug, Colton's point is well received – there's a fair bit of power in that thar gasoline...