## 3 Material and Methods  
### Material  
The material of this study is a data set with a temporal granularity of 15 min and a size of 67,980 rows and 28 columns within the active COVID-19 period in Turkishye between 2 March 2020 and 1 June 2022. The electrical data were mainly acquired from a three-phase energy logger device in connection with the electricity meter belonging to Cukurova University Balcalh Hospital located in Adana, Turkiye in the Eastern Mediterranean as illustrated in Figure 1. Historical lagging hour (\(E_{h}\)), day (\(E_{d}\)), and week (\(E_{u}\)) variables were shifted variations of the actual electricity consumption that may be defined as the target variable (\(E\)) as well. In addition, the average of three-phase root-mean-square (rms) voltages (\(V_{rms}\)) and currents (\(I_{rms}\)) were also obtained from the logger device for investigating the slight variations and effects of power quality on the electricity demand forecasting. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Category** & **Symbol** & **Description** & **Unit** & **Description** & **Description** & **Description** \\ \hline Electrical & \(E_{h}\) & Lagging Hour & kWh & 315.78 & 641.13 & 747.14 & 2094.88 \\  & \(E_{d}\) & Lagging Day & kWh & 315.78 & 640.01 & 746.07 & 2094.88 \\  & \(E_{w}\) & Lagging Week & kWh & 315.78 & 633.35 & 742.35 & 2094.88 \\  & \(V_{rms}\) & Average Voltage & kV & 30.35 & 31.72 & 31.78 & 32.99 \\  & \(I_{rms}\) & Average Current & A & 25.01 & 46.93 & 54.84 & 158.01 \\ \hline  & \(T\) & Temperature & \({}^{\circ}\)C & \(-\)3.21 & 18.59 & 19.30 & 44.36 \\  & \(H\) & Relative Humidity & \% & 8.33 & 59.31 & 57.31 & 100.00 \\  & \(P\) & Pressure & hPa & 968.80 & 986.30 & 986.40 & 1004.60 \\  & \(W_{S}\) & Wind Speed & m/s & 0.01 & 2.56 & 2.84 & 12.32 \\ Meteorological & \(W_{D}\) & Wind Direction & \({}^{\circ}\) & 0.00 & 165.19 & 147.57 & 360.00 \\  & \(R\) & Rainfall & kg/m\({}^{2}\) & 0.00 & 0.00 & 0.01 & 1.99 \\  & \(S_{F}\) & Snowfall & kg/m\({}^{2}\) & 0.00 & 0.00 & 0.00 & 0.40 \\  & \(S_{D}\) & Snow Depth & m & 0.00 & 0.00 & 0.00 & 0.05 \\  & \(I_{SW}\) & Short-Wave Irradiation & Wh/m\({}^{2}\) & 0.00 & 1.01 & 55.90 & 261.82 \\ \hline  & \(\mathcal{C}_{n}\) & Daily New Cases & k & 0 & 9.21 & 18.82 & 111.16 \\  & \(\mathcal{C}_{c}\) & Cumulative Cases & M & 0 & 4.50 & 5.44 & 15.07 \\ \cline{2-6}  & \(\mathcal{R}_{0}\) & & & No Restriction & & 82.13\% \\  & \(\mathcal{R}_{c}\) & Restriction Status & & Curfew & & 6.66\% \\  & \(\mathcal{R}_{l}\) & & & Lockdown & & 8.75\% \\  & \(\mathcal{R}_{fl}\) & & & Full Lockdown & & 2.46\% \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Details of electrical, meteorological, and COVID-19 variables. The meteorological data were extracted from MERRA-2 (Modern-Era Retrospective Analysis for Research and Applications, Version 2) database of the NASA [47]. The geographical coordinates of the site latitude and longitude of the hospital were 37.056 (North) and 35.363 (East), respectively. A total of 9 meteorological variables may be summarized as temperature (\(T\)) and relative humidity (\(H\)) at 2 m above ground, pressure (\(P\)) at ground level, wind speed (\(W_{S}\)) and direction (\(W_{D}\)) at 10 m above ground, rainfall (\(R\)), snowfall (\(S_{F}\)), snow depth (\(S_{D}\)), and short-wave irradiation (\(I_{SW}\)) for incoming short-wave irradiation to the surface, respectively. The calendar data were created by wrangling date/time information in Portable Operating System Interface for Unix (POSIX) format taken from the logger device using Lubridate package [48]. Year (\(y\)), month of year (\(m_{y}\)), week of year (\(w_{y}\)), day of month (\(d_{m}\)), day of week (\(d_{w}\), 1 is Monday), hour of day (\(h_{d}\)), type of day (\(d_{l}\): 0 for working days and 1 for weekends and public holidays), and quarter of hour (\(q_{h}\)) variables were mutated to form calendar variables. The COVID-19 data were meticulously collected from the Turkish Ministries of Health and Interior and crosschecked with the WHO's statistics [49; 50; 51].