The energy required to heat and to cool an apartment varies according to the aspect and situations of the rooms in the apartment, the mode of air-conditioning (all day or intermittent) and the geographical location of the building it is situated in. A year-round computer simulation has been carried out using hourly meteorological information throughout 1975 in each of seven districts — Sapporo, Akita, Tokyo, Nagoya, Osaka, Kagoshima and Naha. The capacity requirements of the equipment, and the total energy requirement for year-round air-conditioning for a room situated in the centre of the south side, middle floor of a building in Tokyo was calculated as the planning guide, varying the situations and directions. The research continued with the study of air-conditioning load ratios for each district, measured by the degree-day and calorie-day index, so that year-round air-conditioning loads in other districts could be easily obtained.