The car use analogy is very poor. Car use is a metered activity, like prepaid cell phone minutes. Your primary expenses are x miles per $3.50+ gallon of gas and car upkeep. If you can't keep your tank filled or your car in proper operating condition, you won't be putting on unlimited miles. Filling your tank and doing preventative maintenance is prepaying to use your car.
Just leave the gas out of the picture and it'll make sense. Or that's just represented in your energy bill. Also the car maintenance: sometimes you need to replace your router, modem, computer. Same thing.