I'm surprised; I've never left the house with anything running that uses significant power and/or water, aside from the fridge and the hot water heater. When I was using laundromats a lot, I would occasionally put a load in and then scoot off to fetch the mail or something, and always get back before it was done; but that exception is because it's a public place with someone watching.
Though on one occasion I ran into a laundromat machine that wasn't filling with water, which meant waiting it out and re-running the cycle in another machine. Had I gone out while that was going on, I would have come back to slightly damp clothes with bits of detergent in them and wondered what had happened.
