The model which simulates nation-wide energy consumption of the residential sector by considering the diversity of household and building types is developed. Since the energy consumption for each household and building category is simulated by the dynamic energy use simulation based on schedule of occupant’s activities and a heating and cooling load calculation model, this model can evaluate various kinds of energy saving policies with considerable accuracy. In addition, average energy efficiency of major home electric appliances used in residential sector and share of housing insulation levels of whole existing houses in each year is predicted by ‘stock model’. In this paper, energy consumption and CO₂ emission by Japanese residential sector until 2025 is predicted. At the BAU case, CO₂ emission will be reduced by 7% from 1990 level. Some additional mitigation measures such as energy efficiency standard for home electric appliances, thermal insulation code, reduction of stand-by power, high efficiency water heaters, energy efficient behavior of occupants, and dissemination of PV are evaluated.

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Expanding energy resources for electric power plants from fossil energies to cost competitive renewable ones are required for reducing GHG emissions and for coping with the soaring in imported fossil energies prices. Importing natural energy resources as storable and transportable hydrogen transformed from wind power electricity may be preferable, if a large quantity of windmills are constructed in the favored oversea regions, such as Patagonia, where steady and strong wind is blowing over wide area and its electricity cost becomes low. Three kinds of electricity generating systems, based on domestic land windmills, domestic offshore windmills and that composed of electric power plant utilizing imported hydrogen, as mentioned above, are designed and the electricity costs of net power flows from such three systems are derived by estimating construction and running costs for the elements of such systems from open references. The result shows that the electricity cost derived from oversea wind power is comparable with that from domestic land wind power, if the future improvements of energy conversion efficiencies of electrolysis and hydrogen liquefaction are considered, though the construction cost for the oversea wind power system is more than twice of that of the domestic land wind power system.

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