## 3 Results
### Economic Optimum Systems of the Five Cases
#### 3.1.3. Costs (NPCs) of the Economic Optimum Systems  
Table 10 shows the costs, in terms of NPC, of the optimal PV systems for the five case studies. The total cost of the system is the sum of the costs of the battery, the PV generator, and others (including ancillary items and financial costs). The latter are not shown in the table, since they hardly varied and are not significant in this study. Table 11 shows the costs of the optimal hybrid systems. It includes one more column with those of diesel generation (diesel genset, O&M and fuel). A comparison of Tables 6, 7, 10 and 11 shows that in PV systems the battery capacity was greater than in hybrid systems, with a greater weight in the NPC of the system. Figure 9 shows the NPCs of the optimal systems, both PV (a) and hybrids (b). They are ordered in terms of their extra costs in PV systems when using a Li-ion battery compared to using a lead-acid battery. Thus, in the pig farm, the NPC of the system had the greatest increase, being more profitable to use a lead-acid battery. On the contrary, in the second home, the NPC of the system had the greatest decrease, being more profitable to use a Li-ion battery. This order is maintained in the graph of hybrid systems (b), although the case of irrigation pumping would actually go from being the second to the third. This is related to the fact that by far the largest reduction of Li-ion battery size was achieved in the hybrid system of the irrigation pumping. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Case** & **Battery Type** & \begin{tabular}{c} **System** \\ **NPC (f)** \\ \end{tabular} & \
\begin{tabular}{c} **Battery** \\ **NPC (f)** \\ \end{tabular} &
\begin{tabular}{c} **PV Generator** \\ **NPC (f)** \\ \end{tabular} \\ \hline \multirow{2}{*}{Winery} & Lead-acid 1  & 656,293 & 232,418 & 331,488 \\  & Li-ion & 707,095 & 248,228 & 358,794 \\ \hline \multirow{2}{*}{Irrigation pumping} & Lead-acid 1  & 590,150 & 302,244 & 199,378 \\  & Li-ion & 673,719 & 208,677 & 366,824 \\ \hline \multirow{2}{*}{Pig farm} & Lead-acid 1  & 1,223,833 & 587,058 & 502,147 \\  & Li-ion & 1,487,218 & 643,730 & 680,034 \\ \hline \multirow{2}{*}{Single-family home} & Lead-acid 1  & 68,077 & 34,681 & 24,704 \\  & Li-ion & 69,679 & 40,589 & 19,484 \\ \hline \multirow{2}{*}{Second home} & Lead-acid & 36,670 & 18,241 & 11,854 \\  & Li-ion 1  & 30,687 & 10,926 & 13,059 \\ \hline \hline \end{tabular}
\end{table} 
Table 10: NPCs of the economic optimum PV systems. Figure 8: Differences in cycled energy and excess energy in the economic optimum systems with Li-ion in relation to lead-acid battery: (**a**) PV systems; (**b**) hybrid systems. All these NPC costs of the systems are the result of the combination of differences in battery and generation costs, which contribute to the NPC of the system as a whole. In summary, from the point of view of cost, again the five cases showed different behaviors by changing the type of battery. On the one hand, Li-ion battery systems used lower capacity batteries that also had a longer lifetime, as shown in the previous section. Thus, as shown in Figure 9a for the PV systems, the NPCs resulting from these batteries was close to or even lesser than that of lead-acid, with differences between \(-40\%\) to \(+17\%\). On the other hand, the costs (NPC) of PV generators increased (\(+8\%\) to \(+84\%\)) due to their higher power, except in the case of single-family home, whose PV power and NPC decreased (\(-21\%\)), as already seen. Finally, only in the case of the second house, the absolute optimal PV system included a Li-ion battery, due to the combination of the largest reduction in the battery NPC and a small increase in the PV generator NPC. In the same way that in PV systems, in hybrid systems Li-ion batteries had lower capacity and longer lifetime, obtaining NPC differences from \(+9.9\%\) to \(-83\%\). As for the generation, since the size of the PV generators is maintained in three cases or decreased in two cases, with NPC differences from \(0\%\) to \(-11\%\).