"Can I borrow some electricity" is a bit of a tongue on a cheek expression to ask people you are visiting to let you charge e.g. your phone. It's usually expected, and even offered by the hosts of you are staying longer. Of course we have lived long enough already with the cell phones everybody knows how vital it is to keep them charged.
With the advent of electric cars the same thing will probably come as common as charging your phone with "borrowed" electricity. But for now it feels a bit weird. Nobody goes visiting friends at the distance and expect to get a refuel on gas. Sure the difference in price between refueling and charging is tenfold.
I was staying over at friends home and while the car should have had enough battery to get home as well as there being charging stations on the way I did ask whether it would be ok for me to borrow a little bit of their electricity. Obviously it was fine with them. Even if the car takes substantially more energy to charge it's still a matter of few euros at max. Unfortunately I can't properly return what I borrowed until they too get an electric car and visit us.