Energy Savings Potential of the Summer Time Concept in Different Regions of Japan from the Perspective of Household Lighting

Summer Time is a convention in which clocks are uniformly set one hour or more ahead of standard time to provide more daylight in the evenings during late spring, summer, and early fall. The main purpose of Summer Time is to make better use of daylight so that it more closely corresponds to our normal daily activities and thus saves energy. Japan is currently not observing Summer Time. This study thus investigated the feasibility of the energy saving potential of Summer Time/Double Summer Time from the perspective of household lighting in Japan and the optimum implementation period. The study found that both the Summer Time and Double Summer Time could reduce household lighting energy consumption, while the magnitude of energy saving potential of Double Summer Time is higher compared to Summer Time. It was also indicated that April-September is the optimum implementation period of Summer Time/Double Summer Time in Japan, from the perspective of household lighting. In terms of geographical location, under Double Summer Time, the household lighting energy saving ratio of the northern Japan regions is higher compared to the southern region. However, under Summer Time, the energy saving ratio of the southern Japan region is significantly higher.