# Assessment of Batteries' Contribution for Optimal Self-Sufficiency in Large Building Complexes
## 4 Discussion  
As it is shown in the current analysis, the average cost of electric energy is approximately 0.2 EUR/kWh in a representative group of hotels in the case of substantial PV with batteries' installation. In particular, comparing these results for each hotel to a benchmark value of electricity supply from grid at 0.15 EUR/kWh, it becomes evident that only Hotel 4 will achieve a profit over the course of 10 years, without any financial support scheme or subsidy. However, it is important to highlight that this investment not only enhances the hotels' energy self-sufficiency and potential for long-term cost reduction but also necessitates a significant initial capital investment. Furthermore, these types of investment offer a strong and robust energy source, enhancing the necessary resilience and mitigating the unwanted energy prices' volatility. Given that both the Greek and European tourism sector is a major energy consumer within the national and European economy, and a significant contributor to the country's and EU's GDP, there exist opportunities for fostering innovation and sustainable investments. These investments should primarily target buildings and facilities, which account for the bulk of energy consumption. Respectively, Crete, a highly popular tourist destination in Greece, experiences seasonal visitation patterns during the energy-intensive summer months. Among the most energy-demanding sectors in the tourism industry is the hospitality sector, where energy needs encompass heating, cooling, lighting, and hot water supply, all reliant on thermal and electrical energy. Electrical energy, in particular, plays a crucial role in powering essential systems and services in hotels, rendering them highly vulnerable to fluctuations in energy prices that can significantly affect operational costs. This paper presents an analysis of the 2022 annual energy consumption of five hotels located on the island of Crete and introduces an algorithm aimed at minimizing capital expenditures (CAPEX), while ensuring a sufficient level of self-sufficiency. To conclude, the hotels should assess their optimal solutions, taking into consideration their special needs and future perspectives, as a sustainable strategy against possible future energy crises and relative price instability that will influence their economic profitability. In parallel, an adequate financial support scheme or subsidy, which will keep the average cost of locally produced electricity significantly lower than 200 EUR/MWh, which is the average electricity price in the current energy market, will boost the energy transition of this specific sector. Regarding the region of Crete, a different type of local subsidy scheme could be implemented in order to minimize the CAPEX required for this kind of investment. Conceptualization, E.K. and M.N. ; methodology, E.K. and M.N. ; validation, M.N., M.M., S.Y. and A.K. ; formal analysis, M.N., M.M. and A.K. ; investigation, M.N., M.M. and A.K. ; resources, M.N., M.M. and A.K. ; writing--original draft preparation, M.N., M.M. and A.K. ; writing--review and editing, M.N., M.M. and S.Y. ; visualization, A.K. ; supervision, E.K. ; project administration, E.K. All authors have read and agreed to the published version of the manuscript. This research received no external funding. The data presented in this study are available on request from the corresponding author. The data are not publicly available due to private ownership. \begin{table}
\begin{tabular}{c c c c} \hline \hline  & **Annual Demand (kWh)** & **CAPEX (EUR)** & **EUR/kWh** \\ \hline Hotel 1 & 5,394,446.90 & 12,150,000 & 0.22 \\ \hline Hotel 2 & 904,832.08 & 1,772,500 & 0.19 \\ \hline Hotel 3 & 973,294.25 & 2,300,000 & 0.23 \\ \hline Hotel 4 & 2,142,032.80 & 2,400,250 & 0.11 \\ \hline Hotel 5 & 3,827,135.55 & 9,500,000 & 0.25 \\ \hline Average: & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Optimal investment analyzed for a payback period of a decade.