No Central AC or Heat
The vast majority of Japanese homes, even those of wealthy people, are not equipped with central heat or air conditioning. Some of the rooms will have wall mounted combo AC heater units, but those units only affect the room that they're in. This is just a cultural difference between the west and Japan. If the Japanese TV commercials can be believed, central A/C and heat is available in Japan, but I have yet to see it actually being implemented in any of the homes that I have visited.
Almost every Japanese home will have one or more portable kerosene heaters (one of mine can be seen in the photo to the right) for use during the winter months. Despite what it may seem, these heaters are not the same as your great grandmother's kerosene heater. These are advanced units with digital readouts and several built in safety mechanisms. Kerosene can be purchased at many Japanese gas stations.