He isn't just bringing a 2gal jug of hot water with him... he'll be running 2gal of hot water through the heat exchanger while keeping it hot, thereby warming the entire car... which WILL hold its heat for a while.
Funny, i realize the robertson is used outside of canada, and I've been rewiring my whole house, so i see that it is the standard with electrical, but it was invented by a canadian and is used mostly here in canada. Read the wiki page
