I never used a hot water bottle before I came to England. My mother had a plug-in electrical heating pad for when we were sick. I'm sure that hot water bottles must exist somewhere in the US, but when I was recently describing one to my American friend, she got the wrong end of the stick and thought that it was meant to be drank from, like a thermos.
Today is freezing cold despite the sunshine, so I may get one last use out of my hottie before spring arrives. My husband's mother sometimes warm the beds for her family with hot water bottles in winter, and there's something very comforting about it. Heat the kettle, fill up the rubber bottle, 'burp it', then slip the fuzzy cover on. It is a nice, cheap, immediate source of heat. Especially useful when we lived in a place that was heated by only a small coal fireplace and some electrical heaters (summer was freezing - we moved out before winter came).
The cover, which is furry and doglike, was bought for me by my husband when I was jonesing for a dog. Now that we have a dog, we sometimes leave him with the hot water bottle if he seems cold. 
