## 5 Conclusions  
The analysis conducted reveals a challenging decision regarding the application of a heat pump system operating in either a monovalent configuration with an electric heater or in a bivalent configuration with a gas boiler. On the one hand, considering the financial aspect, the solution with a gas boiler seems to be more favorable, being cheaper to operate. However, with the use of PV panels, the investment return in a dedicated PV installation is achieved in 6-7 years, but there still remains an annual fee for gas fuel, which is not the case with an electric heater installation. The electric heater solution also offers savings throughout the assumed 15-year lifespan of the installation, amounting to nearly \(\upxi\)3000 more in favor of the EH installation. This is a significant aspect of the issue. On the other hand, an equally important ecological aspect is the release of CO\({}_{2}\) emissions into the atmosphere, which is more favorable with the gas boiler installation, averaging a reduction of between 21.5 and 29.6% when there is no additional PV installation. With the implementation of PV panels, there is a reduction in emissions by approximately 88.3% for the AHP + GB installation powered by a coal-fired power plant, and by 79.1% for a natural gas-fired power plant. In the case of the AHP + EH installation, the use of PV panels results in a 100% reduction in CO\({}_{2}\) emissions, bringing them down to zero annually. Taking into account that the total lifespan of the installation is approximately 15 years, we can estimate the total CO\({}_{2}\) emissions that will occur in the analyzed cases with the use of PV installations. Since the monovalent AHP + EH installation relies entirely on electricity, achieving a 100% reduction in CO\({}_{2}\) emissions allows for the elimination of 756 kg CO\({}_{2}\) from the environment over the 15-year period when powered by electricity produced in a coal-fired power plant. Similarly, for a gas-fired power plant, the avoidable emissions amount to 381 kg of CO\({}_{2}\). This solution fully supports the goals of the 2030 Agenda, which is aimed at reducing greenhouse gas emissions into the atmosphere. In general, the main conclusions from the analysis presented above can be condensed into:  
1. Financial aspects: * The gas boiler solution is cheaper to operate; * PV panel investment return in 6-7 years; * Electric heater (EH) installation has no annual gas fuel fee; \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & & \multicolumn{2}{c}{**AHP + EH**} & \multicolumn{2}{c}{**AHP + GB**} \\ \hline \multirow{2}{*}{**Year**} & **PV Installation** & **Yearly Cost** & **Cash Flow** & **PV Installation** & **Yearly Cost** & **Cash Flow** \\  & **Cost** & **without PV** & **Cash Flow** & **Cost** & **with PV** & **Cash Flow** \\ \hline \multicolumn{5}{c}{**Euro**} & **Euro/a** & **Euro/a** & **Euro** & **Euro/a** & **Euro/a** \\ \hline
1 & 14,800 & 2947 & \(-\)17,747 & 9500 & 2321 & \(-\)11,821 \\ \hline
2 & 0 & 2947 & \(-\)14,800 & 0 & 2321 & \(-\)9500 \\ \hline
3 & 0 & 2947 & \(-\)11,853 & 0 & 2321 & \(-\)7179 \\ \hline
4 & 0 & 2947 & \(-\)8905 & 0 & 2321 & \(-\)4859 \\ \hline
5 & 0 & 2947 & \(-\)5958 & 0 & 2321 & \(-\)2538 \\ \hline
6 & 0 & 2947 & \(-\)3010 & 0 & 2321 & \(-\)218 \\ \hline
7 & 0 & 2947 & \(-\)63 & 0 & 2321 & 2103 \\ \hline
8 & 0 & 2947 & 2884 & 0 & 2321 & 4424 \\ \hline
9 & 0 & 2947 & 5832 & 0 & 2321 & 6744 \\ \hline
10 & 0 & 2947 & 8779 & 0 & 2321 & 9065 \\ \hline
11 & 0 & 2947 & 11,727 & 0 & 2321 & 11,385 \\ \hline
12 & 0 & 2947 & 14,674 & 0 & 2321 & 13,706 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Comparison of cash flows in a system with PV panels. * EH installation saves nearly \(\xi\)3000 more over a 15-year lifespan. * Ecological aspects:
* Gas boiler installation reduces CO2 emissions by 21.5-29.6% without PV panels;
* PV panels reduce CO2 emissions by 88.3% (coal-fired power) and 79.1% (natural gas-fired power) for AHP + EH.