## 5 Conclusions  
The focus of this study is on state-of-the-art research on ZEBs and energy efficiency towards sustainability. In order to give deeper insights into research gaps and needs, a bibliometric review method was utilized. The ZEB and energy efficiency pattern for sustainability in the twenty-first century was found to be highly comparable with the twentieth. Furthermore, _Energy and Buildings_ has contributed the most to ZEBs and energy efficiency towards sustainability. Moreover, in research articles on ZEBs and energy efficiency, the USA has the greatest influence. In terms of theory, this research is unique in the following ways; (a) a thorough literature review on bibliometrically advanced research on ZEBs and energy efficiency towards sustainability is presented; (b) the research focuses on ZEBs and energy efficiency contexts, including new techniques, emerging trends, and future directions; (c) the research offers guidance as to how to address the deficiencies in additional research definition. This study has limits despite its contributions. Firstly, the data was extracted from a Scopus database. Further data can gathered for quantitative and qualitative assessments by merging data from multiple databases (e.g., Google Scholar. Web of Science, and so on). Second, this research was confined exclusively to journal publications only. The foregoing \begin{table}
\begin{tabular}{c c c c c c c c c c c c c c} \hline \hline \multirow{4}{*}{**PV System Variant**} & \multirow{4}{*}{\
\begin{tabular}{c} **Electrical** \\ **Energy** \\ **Consumption** \\ \end{tabular} } & \multicolumn{4}{c}{**Current**} & \multicolumn{4}{c}{**Transmission**} & \multirow{4}{*}{
\begin{tabular}{c} **Required** \\ **Amount of** \\ **Grid, with a** \\ **Energy** \\ \end{tabular} } \\  & & **Consumption** & & & **Energy** & & **20\% Allowance** & & **20\% Allowance** & & **Production** \\  & & & & & & & & & & & & \\ \hline Variant I & 3059 & 918 & 2570 & 3488 & 7524 & 3488 & 7524 & 3488 & 7524 & \\ Variant II & 6600 & 1980 & 1980 & 5544 & 7524 & 348 & 7524 & \\ \hline \hline \end{tabular}
\end{table} 
Table 6: The required amount of electrical energy production in analyzed variants. \begin{table}
\begin{tabular}{c c c c c c c c c c c c c c} \hline \hline \multirow{2}{*}{\
\begin{tabular}{c} **Data/PV** \\ **System Variant** \\ \end{tabular} } & \multicolumn{8}{c}{**Month**} & \multirow{2}{*}{**Units**} \\  & & & & & & & & & & & & & & & \\ \cline{2-13}  & **I** & **II** & **III** & **IV** & **V** & **VI** & **VII** & **VIII** & **IX** & **X** & **XI** & **XII** & **Annual** & **Units** \\ \hline \multicolumn{13}{c}{**Unit Value of Solar Radiation Energy \(I_{sol}\)**} \\ \hline
\begin{tabular}{c} Meteorological \\ data, S, 15\({}^{\circ}\) \\ (roof slope) \\ \end{tabular} & 24.240 & 31.894 & 64.207 & 97.280 & 139.912 & 143.628 & 140.486 & 119.367 & 90.563 & 44.202 & 21.919 & 16.900 & 934.595 & kWh/m\({}^{2}\) \\ \hline \multicolumn{13}{c}{Electrical energy production of the PV system \(E_{PV}\)} \\ \hline Variant I & 93.2 & 122.6 & 246.9 & 374.1 & 538.0 & 552.3 & 540.2 & 459.0 & 348.2 & 170.0 & 84.3 & 65.0 & 3594 & kWh \\ \hline Variant II & 195.7 & 257.5 & 518.5 & 785.5 & 1129.8 & 1159.8 & 1134.4 & 963.9 & 731.3 & 356.9 & 177.0 & 136.5 & 7547 & \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Electrical energy production of the PV system \(E_{PV}\)restrictions present wonderful opportunities for further research, yet when evaluating the outcomes of the research they should be taken into consideration. Nevertheless, in future studies, data from different sources and characteristics may be employed to overcome limits in literary impact assessments, coherence, and links. The monitoring of energy consumption by buildings allows the verification of calculation assumptions by the actual thermal quality of buildings in specific climatic conditions. The obtained results can be a very important source of information for the analysis of the possibility of erecting a building with low energy demands in areas of temperate continental climate.