In 1965,the national average for Japan's residential energy consumption per household was 21.3 GJ/household/year. By 1999,it had increased 2.2-fold to 47.0 GJ/household/year, showing an average annual growth rate 2.4% over the past 34 years. This means that trends in residential energy consumption in Japan run counter to the trends in other developed countries, where their residential energy consumption is almost stable or decreasing. The main reason for this is that Japanese living standards have been and still is logging behind those of developed nations. Other factors, which explain differences in household energy use, are climatic conditions, traditional lifestyles, relative energy prices, differences in building stock and so on. These differences affect mainly space heating energy consumption. Space heating method in Japan differs from that of developed nations. Analysis on energy consumption structure and its diversified factors is sine qua non when arguing the energy conservation measures. In addition to this, the measures to curtail the stand-by electricity recently focused should be taken. A significant amount of electricity is wasted while appliances are in the stand-by mode. This waste should make us reconsider our notions of convenience, and comfort. The forecast by the econometrics model reveals that the residential useful energy consumption per household will slightly increase in spite of decreasing number of household and increasing insulation level of house stock.