## 4 Discussion and Conclusions  
The creation of energy communities is a new trend in the energy sector and leads to the creation of decentralized energy networks. Such independent units are consequently more resistant to power supply failures. This situation is also confirmed by several recent studies [1, 5, 12, 14, 15, 16, 20]. The presented community is located in the city of Zilina in Slovakia, part of the EU. As it was presented, in the community, there are houses in their original condition, houses partially reconstructed, and there are also new houses. The simulation of such a larger number of buildings can be performed in several ways, as shown by studies [30, 32, 34]. It is also possible to use the sampling method, whereby the buildings in the city are replaced by some representative sample, as presented in the study [35]. Finally, for this study, the method described in [36] was used, where the authors describe the possibilities of building renovation and possible savings. To simulate the energy community, three reference buildings were selected based on the survey, for which the energy consumption was simulated. The simulation pointed to a considerably high heat demand. This high price showed the necessity of restoring family homes in this community. Therefore, in the second step, the impact of retrofit measures was simulated. The known initial state and state after retrofit made it possible to calculate the expected energy savings for heating for each house in the respective energy class. The simulation results showed a reduction in energy consumption similar to studies presented in [36]. The reduction of heat demand will also enable the installation of a renewable energy source and a heat pump for heating. According to study [37], the use of RES is associated with several limitations, while it is appropriate if the energy is consumed directly at the place of production. For this reason, two alternatives of the installed power of photovoltaic panels were simulated. The subsequent simulation of the use of solar energy pointed to the reduction of dependence on the supply of energy from external sources and the coverage of a significant part of energy consumption. Such a procedure would make it possible to significantly reduce CO\({}_{2}\) emissions, which is consistent with studies [38, 39]. Even the smaller installed power of the photovoltaic system is sufficient to cover the energy needs of most houses after the restoration of the houses, which would have a direct impact on the return of the system [40, 41]. The different installed power options for individual houses are ultimately an advantage of the created community, as the surplus energy produced in one house is consumed in another house from the community while not burdening the transmission lines. The creation of such small communities can be very beneficial and represents a possible next development in energy supply with regard to efficient and environmentally acceptable operation [42]. Creating such communities would also lead to a reduction in overall fuel consumption, which would ultimately contribute to the creation of fully renewable energy systems [43]. As simulation showed, in the case of Slovakia, a country with a lower number of sunny days, even smaller photovoltaic installations can cover a significant part of energy demand. During winter months, there is still a need to purchase energy or use long-term energy storage systems. Conceptualization, P.D. and R.N. ; writing, review and editing, P.D. and B.Z. ; All authors have read and agreed to the published version of the manuscript. This research is supported by the project \"Use of hydrogen as ingredients in gas for heat and electricity production\", UNIZA 2021. This research is supported by the project KEGA--032 ZU-4/2022, \"Implementation of knowledge about modern ways of reducing the burden on the environment in the energetic use of solid fuels and waste into the pedagogical process\" and by DAAD Germany academic fund--Nr. 91873299. Not applicable.