## 4 Discussion
### Price of Components and Fuel  
In the calculation of costs, three price parameters are involved--that of the photovoltaic modules, that of the batteries, and that of the fuel to make up for the deficit in solar generation. These three prices tend to change in the short to medium term, so it is interesting to study how the optimal system varies with them.  
First, the system is analyzed with the variation in the price of PV modules, which have suffered a significant price decrease in the last decade (Figure 19).  
As seen in Figure 19, the optimal storage capacity is not affected by the price of the modules. As expected, the optimal installed power increases as the price decreases. From these data, a better conclusion can be drawn from Figure 20.  
The reliability of the system increases with the decrease in the price of the panels, for which reason, having a very oversized installation power to charge the battery enough to  
Figure 19: Variation of power and optimal capacity with the price of PV modules.  
Figure 20: Variation of power and optimal capacity with the price of the modules.  
fully supply the periods of lower generation and eliminate the cost of fuel consumption is prioritized.  
Analyzing the evolution of the system and setting all the parameters except the price of battery storage, a similar effect is observed (Figure 21).  
Installed power remains practically constant, decreasing slightly as storage capacity increases. Meanwhile, storage capacity skyrockets for low storage prices, increasing supply reliability (Figure 22).  
In this case, the difference is even more exaggerated, since an equal percentage variation in the price of the batteries is much more significant than in the case of PV modules, making the need for a secondary generator practically zero when the price is cheaper. Given current prices (approx. 0.5 EUR/W for PV modules and 0.6 EUR/Wh for batteries), a USD 0.1 decrease in batteries would produce approximately a 1.5% increase in reliability and a EUR 200 decrease in cost system, while the same variation in PV modules would produce only a 0.2% improvement in reliability and less than EUR 50 decrease in cost, concluding that the price of energy storage is much more significant in the system.  
Finally, the same analysis is conducted for the price of fuel, which generally fluctuates more frequently than component prices (Figure 23).  
Figure 21: Variation of the power and optimal capacity with the price of the batteries.  
Figure 22: Variation of the reliability and cost of the system with the price of the batteries.  
It can be seen in Figure 23 how a price increase gives rise to an identical reaction in the two main components of the system, increasing installed power and storage capacity, with the consequent increase in supply reliability and annual cost (Figure 24).  
Inevitably, an increase in the cost of fuel has an equal reflection on the total cost of the installation. The cost of increasing the power and capacity of the system without fuel is less than the increase in the cost of fuel to cover the hours of solar supply failure, but it also translates into an increase in the total cost. Regardless of this study, if macroeconomic effects are considered, an increase in the price of fuel may cause an increase in the price of the rest of the products, modifying the trend curves previously seen.