One of the big differences between Japan and the United States is central heat. In short, the Japanese don’t have it. Instead of heating their buildings, they heat their bodies.
Here’s an interesting account of an American taking a Japanese approach to staying warm in the winter: “Micro heaters cut 87% off my electric heat bill“
Our family just converted this year from heating oil to solar hot water and electric heat. We’ve taken some other steps to reduce our energy use, but despite living in Japan for a year, we still haven’t mastered the art of personal space heating. I’m looking forward to trying some new ideas to stay more comfortable using a lot less energy.