**3. Research Methods**

## *3.1. Determinants of the Selection of the Research Period*

As mentioned in Section 2, electricity consumption data were available for enterprises operating in the catering and hotel industry for the period from 1 January 2018 to 31 May 2021.

However, the authors were particularly interested in the impact of the COVID-19 pandemic on changing the characteristics of electricity consumption in the analyzed sectors of the economy.

The World Health Organization (WHO) on 14 January 2020 issued a warning against the spread of SARS-COV-2, and then, on 30 January 2020, assessed that the spread of the new pathogen poses a threat to public health of international scope. Ultimately, on 11 March, WHO declared SARS-CoV-2 to be a pandemic [49].

The unprecedented scale of subsequent restrictions imposed by governments as part of counteracting the development of the pandemic in subsequent waves of COVID-19, significantly restricting the freedom to perform previously routine everyday activities, has left its mark, especially on sectors related to people-to-people contacts. The forced change in the behavior of society, especially during the first wave in March and April 2020, from the energy point of view, caused problems in maintaining grid stability and adjusting the volume of energy production to unpredictably fluctuating demand. Thus, the black swan in the form of the new coronavirus pandemic has caused operational and financial difficulties for energy companies [50].

The restrictions regulated by legislation introduced during the pandemic waves, obviously influencing the freedom of everyday activities, influenced the amount of electricity demand in industries related to gastronomy, tourism or broadly understood entertainment (where there was a large concentration of people in closed spaces). However, the impact of behavioral changes in society in the face of growing negative moods is intuitively difficult to determine [51].

Therefore, for a detailed analysis, the time from 5 March 2020 to 31 May 2021 was assumed as a disturbed pandemic period. This is the period starting from the day following 4 March 2020, in which the first case of SARS-COV2 infection was diagnosed in Poland—the so-called "patient zero" [49]. This date was adopted as the limit of the change in the public awareness of the nature of the problem from global to national, which could have caused a spontaneous change in behavior, regardless of the restrictions introduced later.

On the other hand, the reference point was the same period in the previous years, that is, the interval from 5 March 2018 to 31 May 2019.
