## 5 Results and Discussion
### Discussion  
Overall, from the results obtained, it is clear that, with the present costs of battery storage, it is implausible to make a profit only by increasing self-consumption.  
However, it is clear that, in the long run, with the expected drop in storage prices, there is an enormous potential for investments in PV-BESS on Madeira Island. For example, with BESS prices around 250 \(\upxi\)/kWh, many combinations are already profitable. This result is well aligned with other works, which suggest that, if the price of storage drops and the buying electricity increases, the payback time will be reduced and profitability reached in many cases [2, 4, 18, 20, 22].  
Furthermore, the low number of cycles is also an indicator that degradation will be mostly calendric. Therefore, even if storage devices do not see an accentuated drop in the cost of acquisition, an extended calendar life would also contribute to making PV-BESS profitable in the long run.  
\begin{table}
\begin{tabular}{c c c c c c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**ID**} & \multirow{2}{*}{**C**} & \multirow{2}{*}{**Savings**} & \multicolumn{6}{c}{**Greedy \(\upxi\) PC G-TOU Taifif**} \\  & & & \multicolumn{3}{c}{**Balance Per I invested (\%)**} & \multicolumn{3}{c}{**Payback Time (Vears)**} & \multicolumn{3}{c}{**Savings**} & \multicolumn{3}{c}{**Balance Per I invested (\%)**} & \multicolumn{3}{c}{**Psayback Time (Vears)**} \\  & & & \multicolumn{3}{c}{**\(\upxi\)/kWh**} & \multicolumn{3}{c}{Present –50\% -75\% } & \multicolumn{3}{c}{Present –50\% -75\% } & \multicolumn{3}{c}{Present –50\% -75\% } & \multicolumn{3}{c}{Present –50\% -75\% } & \multicolumn{3}{c}{Present –50\% -75\% } & \multicolumn{3}{c}{Present –50\% -75\% } & \multicolumn{3}{c}{Present –55\% -75\% } \\ \hline  & A1 & 276 & 115 & 81.6 & -32.2 & -24.4 & 54.3 & 27.2 & 13.6 & 992 & 247 & 60.8 & -21.1 & **57.9** & 25.3 & 12.7 & **6.3** \\ A & A2 & - & - & - & - & - & - & -  
The obtained results also highlight a significant trade-off between the size of storage, control strategy, and profitability. In fact, higher profits happen in the 2-TOU tariff with the smallest storage combo available. This, however, leads to the lowest rates of SC and, in turn, higher levels of renewable energy curtailment. On the other hand, using the greedy strategy, the SC rates will increase with the storage capacity. However, due to the highest initial investment, the profitability drops considerably.  
Ultimately, with the tariffs and legislation currently in place on Madeira Island, there is a perverse incentive towards favoring the curtailment of solar PV production over increasing the levels of SC. This result is also aligned with the literature, where it is suggested that the profitability of battery energy storage systems is highly sensitive to the underlying regulation frameworks, which makes investing in storage potentially risky in the long run [2, 15].  
Ultimately, our work suggests that new legislation and price mechanisms must be employed on Madeira Island, such that self-consumption is not just the more sustainable option, but also the most profitable one. For example, a net-metering tariff for excess production would avoid curtailment while still enabling the consumer to select the most profitable control strategy. Another possibility would be a dynamic feed-in tariff for injecting from storage to the grid. This would allow larger storage devices to complete at least one cycle per day, therefore adding to the profitability even in the absence of a sufficiently large solar PV installation.