Hot water bottles are known as "Yutanpo" in Japan and have long been used as bed heaters. Come winter or cold nights in general, they provide an inexpensive alternative heat source for those who can't afford it or don't want to turn on the central heating. Yutanpo is excellent for keeping beds warm and warming feet in the office or while working at home.

Compared to western rubber hot water bottles, Yutanpo can keep you warm for up to 12 hours without the rubbery smell. Just like rubber hot water bottles, they must be wrapped in a cloth or cover to prevent direct contact with your skin.

Turning down the heat a few degrees at night and using a Yutanpo instead will be easier on your wallet. And the environment.