This paper focused on the impact of lifestyle changes in response to the novel coronavirus infection (COVID-19) on the electricity demand of 1398 detached houses during Apr. 2020–Sep. 2020. The rate of increase in power consumption excluding space cooling was the largest in April with an average of 19% for all households. The reason of this increase was analyzed with questionnaire survey. 87 households with room air conditioners consumed more space cooling power in August than usual at an increase of 23%. Power consumption of the centralized air conditioner was less affected than that of the room air conditioner.