While it’s hard to avoid using electric heaters (space heaters, kerosene heaters, and kotatsu) while at home in the winter, you can reduce your overnight electric use by using a hot water bottle to stay warm in bed. Sold at home-goods stores, the Japanese 湯たんぽ (yutanpo) are hot water bottles made of durable hard plastic and come with a soft cover.
I have an あったかカラフル湯たんぽ (attaka karafuru yutanpo; Warm Colorful Hot Water Bottle) brand water bottle. This water bottle holds 600 ml of hot water (3 Japanese cups); is available in a variety of bright colors; and comes with a delightfully fuzzy washable polyester cover for about 1000 yen. (MSRP is 1200 yen, but I’ve seen them for less.)
To use, just fill up the bottle with hot water from your kettle. Boiling water won’t melt the plastic, and the thick plastic and cloth cover will protect your skin. Pop it between your blankets and your futon before you go to bed and it’ll keep the bed warm all night.
Although you have to use electricity or gas to boil the water, you’ll be using less than running an electric blanket or space heater all night. Also, you can use the still-warm water to wash up in the morning, which means not wasting water if your tap is slow to heat. (Assuming you have a hot water tap in the bathroom.) Definitely win-win.
Leah Zoller is a first-year CIR in Anamizu and doesn’t run her heaters overnight.