  As of May 2022, the coronavirus disease 2019 (COVID-19) still has a severe
global impact on people's lives. Previous studies have reported that COVID-19
decreased the electricity demand in early 2020. However, our study found that
the electricity demand increased in summer and winter even when the infection
was widespread. The fact that the event has continued over two years suggests
that it is essential to introduce the method which can estimate the impact of
the event for long period considering seasonal fluctuations. We employed the
Bayesian structural time-series model to estimate the causal impact of COVID-19
on electricity demand in Japan. The results indicate that behavioral
restrictions due to COVID-19 decreased the daily electricity demand (-5.1% in
weekdays, -6.1% in holidays) in April and May 2020 as indicated by previous
studies. However, even in 2020, the results show that the demand increases in
the hot summer and cold winter (the increasing rate is +14% in the period from
1st August to 15th September 2020, and +7.6% from 16th December 2020 to 15th
January 2021). This study shows that the significant decrease in electricity
demand for the business sector exceeded the increase in demand for the
household sector in April and May 2020; however, the increase in demand for the
households exceeded the decrease in demand for the business in hot summer and
cold winter periods. Our result also implies that it is possible to run out of
electricity when people's behavior changes even if they are less active.
