# A Complete and High-Resolution Estimate of Sardinia's Rootrop Photovoltaic Potential
## 5 Discussion  
Our procedure estimated a yearly production of 239 kWh per m\({}^{2}\), i.e., a photovoltaic potential of 22 TWh distributed over a rooftop area of about 92 km\({}^{2}\). The JRC [7] estimates, for the region of Sardinia, a production of 4.68 TWh, but over an area of just 31.96 km\({}^{2}\), corresponding to an average of 146.41 kWh per m\({}^{2}\). It is not explicit in the text, but it would appear that they used a panel efficiency of 10% instead of 18.2% (as in our case). Using the 18.2% efficiency (5.5 m\({}^{2}\)/kWp instead of 10), results in an annual production of 266.19 kWh/m\({}^{2}\). The JRC estimate was, thus, higher than ours, although this can be explained by their characterization of the modules with optimal aspect (due south) and slope (20\({}^{\circ}\)) and not, as in our case, with the actual tilt and orientation of the rooftops. The JRC estimate, moreover, is based on much coarser analysis that does not take into account the actual location of the buildings or the orientation of the rooftops. Sardinia's electricity production in 2019 (pre-COVID-19) was 13.14 TWh, with photovoltaic systems accounting for only 8.8% (1.15 TWh), while total consumption was 8.47 TWh [50]. As for the domestic and tertiary sectors, consumption in 2019 amounted to 4.43 TWh. The photovoltaic potential of Sardinia is therefore capable of easily covering domestic and tertiary sector consumption, and that in the industrial and agricultural sectors. Consumption and potential per province are detailed in Table 2. The smaller available surface area per inhabitant and the higher concentration of tertiary sector enterprises render the province of the metropolitan city of Cagliari the most energy-intensive with respect to its photovoltaic potential. This is despite the fact that the installation of modules on just one third of the total rooftop surface could meet the energy needs of all households and services. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Province** & **Energy Demand** & **PV Potential** &
\begin{tabular}{c} **\% of Rooftop** \\ **Surface** \\ \end{tabular} \\ \hline Cagliari & 1248 GWh & 3.80 TWh & 32.84\% \\ \hline Nuoro & 482 GWh & 2.95 TWh & 16.34\% \\ \hline Oristano & 374 GWh & 3.15 TWh & 11.87\% \\ \hline Sassari & 1514 GWh & 6.65 TWh & 22.77\% \\ \hline Sud Sardegna & 810 GWh & 5.49 TWh & 14.75\% \\ \hline Sardinia & 4.43 TWh & 22.04 TWh & 20.10\% \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Electricity consumption in the domestic and services sectors, and photovoltaic potential for the 5 provinces of Sardinia. The percentage indicates the fraction of eligible rooftops that, if equipped with a photovoltaic system and accumulators, would cover the needs of the domestic and services sectors. Figure 11: Average annual energy production per m\({}^{2}\) based on the orientation and inclination of photovoltaic panels in Sardinia. The distribution of the estimated values for the levelized cost of electricity is shown in Figure 12, where 50% of installations had an LCOE below 14.76 EuroCent/kWh, and 50% of installations had an LCOE between 13.94 and 16.10 EuroCent/kWh. Figure 13 shows the total energy from rooftop PV as a function of the corresponding levelized cost of electricity, and shows that almost all of the available roof area could be exploited for an LCOE of 17.5 EuroCent/kWh. In Italy, electricity prices in 2022 soared above 30 EuroCent per kWh, making photovoltaic system installation worthwhile even in the least productive locations [51]. Assuming  
Figure 12: Distribution of the levelized cost of electricity for all the rooftop surfaces in Sardinia. Figure 13: Cumulative sum of energy for all the rooftop surfaces in Sardinia as a function of the levelized cost of electricity. a return to the situation prior to COVID and to quieter geopolitical circumstances, the average energy price from 2010 to 2019 was 9.45 EuroCent/kWh, well below our LCOE values.