This paper presents a study of the impact of urban warming upon energy consumption forair-conditioning in the home, using a numerical simulation model. The results are as follows. 1) In citiesother than Sapporo and Sendai, about 50% of the total hours of occupancy were ventilation hours, andabout 20% to 40% were cooling hours. As a result, the total energy consumption for cooling wascomparatively large. 2) In these other cities, cooling hours increased in the summer as the outdoortemperature rose. In particular, when the temperature rose by 3C, air-conditioning time increasednonlinearly in response. However, the increase in energy consumption for cooling was broadly linear. 3)In Sapporo, a temperature rise of 5C was accompanied by 7 cooling days, whereas a 6C rise broughtabout 14 cooling days.