*4.3. Pre-Pandemic Period*

To facilitate the interpretation and readability of the matrix, the functionality of the "pairs.panels" function ("psych" RStudio library) was used, which differentiates the font size of the given values of correlation coefficients depending on their size. For absolute values close to 1 (full correlation), the font has a target size, and for values tending to zero (no correlation) the font is fading out.

When analyzing the results included in the Pearson and Spearman correlation matrices in the pre-pandemic period (Figures 13 and 14) and the values of correlation coefficients collected in tabular form (Tables 3 and 4), it should be stated that the highest degree of similarity (relationships) is shown by the restaurants marked R1 and R5, for which the r-Pearson correlation coefficient was 0.82, which should be interpreted as the existence of a strong linear correlation. Spearman's rho coefficient was slightly lower, that is, 0.78. Similarly, the cases of R1, R2, R4, R5 and R6 showed a strong almost linear relationship, as the values of both statistics here are over 0.7. Hotels H2 and H4 and cafes C1 and C3 show a slightly lower value, but which can already be interpreted as the average strength of correlation. In the linear Pearson correlation to the power demand profile in the National Power System, only the C2 café case showed a value above 0.5 (average correlation), although most enterprises achieved values above 0.4 (moderate correlation). It is worth noting, however, that Spearman's rho-statistic showed the existence of a much stronger non-linear relationship in the case of C3 cafes with the Spearman correlation coefficient at the level of 0.69 and 0.55 for the R3 restaurant.

With regard to the insolation conditions, and thus the productivity of a potential PV installation, the highest value of non-linear correlation at the level of 0.65 was achieved by the case of the C3 café. The H3 hotel recorded a slightly worse result (0.60).

**Table 3.** The values of correlation coefficients between hourly electricity consumption and load of Power System. Description of colors: Green = positive. Red = negative. Ascending order: from light (near zero) to dark (near 1) color.


Source: own study.

**Table 4.** The values of the correlation coefficients between hourly electricity consumption and horizontal insolation. Description of colors: Green = positive. Red = negative. Ascending order: from light (near zero) to dark (near 1) color.


Source: own study.
