## 5 Results of the Analysis  
The technical-economic comparison of the proposed solutions was made over a study period equal to a lifetime of 20 years for both proposed solutions, based on the calculation of economic performance indicators with updated values: the net present value (NPV), the internal rate of return (IRR), and the payback period (PP) [11,12]. The considerations and hypotheses mentioned in the previous paragraphs were taken into account. The components of the income and expenditure flows related to the analysed solutions are presented in Table 2.  
The values of the economic performance indicators calculated for the analysed solutions, in the \"University Politehnica of Bucharest (UPB) Investment option\", are summarized in Table 3.  
The optimal solution is one in which the following occurs:  
* Virtual receipts of annual costs related to \"virtual sales\" of the entire amount of heat produced by the implementation of the proposed scheme are considered as income. * The price of the \"sold\" heat is considered equal to the price in the UPB invoice. * The value of the investment is equal to the quota provided by the UPB budget. The summary of the results of the technical-economic analysis is presented in Table 4, while in Figure 2, the evolution curve of the payback period for all analysed scenarios is shown. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{
\begin{tabular}{c} **Economic** \\ **Performance** \\ **Indicator** \\ \end{tabular} } & \multicolumn{2}{c}{**Scenario 1**} & \multicolumn{2}{c}{**Scenario 2**} & \multicolumn{2}{c}{**Scenario 3**} \\ \cline{2-7}  & **UPB** & **Total** & **UPB** & **Total** & **UPB** & **Total** \\  & **Investment Share** & **Investment** & **Investment Share** & **Investment** & **Investment Share** & **Investment** \\ \hline \hline
**NPV [EUR]** & \(55\),\(482\) & \(-172\),\(265\) & \(140\),\(877\) & \(-86\),\(870\) & \(96\),\(857\) & \(-130\),\(890\) \\ \hline
**PP [years]** & \(7.80\) & \(>\)lifetime & \(4\) & \(>\)lifetime & \(5.2\) & \(>\)lifetime \\ \hline
**GPP [years]** & \(6.58\) & \(35.37\) & \(3.66\) & \(19.71\) & \(4.75\) & \(25.54\) \\ \hline
**IRR [\%]** & \(14.13\%\) & \(-5.57\%\) & \(27.07\%\) & \(0.14\%\) & \(20.56\%\) & \(-2.22\%\) \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Technical-economic analysis results. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{
\begin{tabular}{c} **Scenario 1** \\ **Type of Cost [EUR]** \\ **Type of Cost [EUR]** \\ **Investment Share** \\ \end{tabular} } & \multicolumn{2}{c}{**Scenario 1**} & \multicolumn{2}{c}{**Scenario 2**} & \multicolumn{2}{c}{**Scenario 3**} \\ \cline{2-7}  & **UPB** & **Total** & **UPB** & **Total** & **UPB** & **Total** \\  & **Investment Share** & **Investment** & **Investment Share** & **Investment Share** & **Investment** \\ \hline
**Total investment [EUR]** & \(52\),\(000\) & \(279\),\(747\) & \(52\),\(000\) & \(279\),\(747\) & \(52\),\(000\) & \(279\),\(747\) \\ \hline
**Specific investment [EUR/AWI]** & \(812.5\) & \(4371\) & \(812.5\) & \(4371\) & \(812.5\) & \(4371\) \\ \hline
**Total annual expenses [EUR/year]** & \(-5992\) & \(-5992\) & \(5609\) & \(5609\) & \(765\) & \(765\) \\ \hline
**Specific expenses [EUR/AW year]** & \(93.7\) & \(93.7\) & \(87.7\) & \(87.7\) & \(12\) & \(12\) \\ \hline
**Sales receipts [EUR/year]** & \(1916\) & \(1916\) & \(19\),\(801\) & \(19\),\(801\) & \(11\),\(718\) & \(11\),\(718\) \\ \hline
**Annual revenue [EUR/year]** & \(7909\) & \(7909\) & \(14\),\(192\) & \(14\),\(192\) & \(10\),\(953\) & \(10\),\(953\) \\ \hline \hline \end{tabular} Note: Negative values indicate cost savings.  
\end{table} 
Table 2: Income and expenditure flows for the analysed scenarios.