Electric companies usually price electricity in kilowatthours, with an
average kilowatthour costing about 12 cents.
While this sounds fairly cheap, they could do even better by pricing
in joules. At 12 cents per kilowatthour, a joule costs about 0.0000033
pennies. That’s about 300,000 joules per penny or 30 million joules
Of course, this won’t change the actual price of electricity (or the
fact that my air conditioner burns $300 worth of electricity every
July), but it might be a cute advertising gimmick.