# Cost-Benefit Analysis of Small-Scale Rooftop PV Systems: The Case of Dragotin, Croatia
## 2 Materials and Methods
### Insulation and Electricity Produced from PV Systems  
Data on insolation and electricity production required for cost-effectiveness analysis were taken from the report prepared using Solargis Prospect [24] for the Dragotin location according to the given parameters. These data are shown in Table 5, taking into account losses in the system. Losses in the PV system that occur during energy conversion are difficult to quantify accurately, but it is important to take them into account when designing and installing the system. The most important losses to be considered are according to [33; 34]:  
1. Losses in the inverter;
2. Ohmic losses that occur as a result of resistance to current flow from the AC side of the inverter and in the cables;  
Figure 5: Hourly load curve. \begin{table}
\begin{tabular}{c c c c c c c c c c c c} \hline \hline
**Hours** & **January** & **February** & **March** & **April** & **May** & **June** & **July** & **August** & **September** & **October** & **November** & **December** \\ \hline
0–1 & 0 & 0 & 0 & 0 & 0 & 0 & 0 & 0 & 0 & 0 & 0 & 0 \\
1–2 & 0 & 0 & 0 & 0 & 0 & 0 & 0 & 0 & 0 & 0 & 0 \\
2–3 & 0 & 0 & 0 & 0 & 0 & 0 & 0 & 0 & 0 & 0 & 0 \\
3–4 & 0 & 0 & 0 & 0 & 0 & 0 & 0 & 0 & 0 & 0 & 0 \\
4–5 & 0 & 0 & 1 & 14 & 31 & 18 & 0 & 0 & 0 & 0 & 0 \\
5–6 & 0 & 0 & 1 & 48 & 159 & 188 & 15  
3 Losses due to dust or snow on the surface of the PV module;
4 Losses of auxiliary devices. For a given PV system and object location, theoretical losses are defined and shown in Figure 6.  
The average daily production and consumption of electricity for each month is calculated based on the measured hourly electricity consumption and hourly electricity production (according to Table 5). The profile with 1-h time steps is most often applied [35; 36]. Figure 7 shows an example of the electricity consumption and production profile for the month of January. The choice of the measurement time interval has an impact on the appearance of the electricity consumption profile, i.e., on the results of the analysis. Steps of 5 min, 15 min, and 1 h are mentioned in the literature. The longer the time step, the higher the amounts for (SC) and (SS). The difference between (SC) for a step of 5 min and 1 h on an annual basis can be 3.2%, while daily it can be more than 5% [4]. Accordingly, for our case of selecting a time step of 1 h, it can be assumed that the error in the analysis results does not exceed 5%. In general, production and consumption profiles rarely match, leading to a low \(SS\) or \(SC\) value. In the case of excess electricity (production greater than consumption), unused  
Figure 6: Theoretical losses in a given PV system [24]. Figure 7: Average hourly profile of electricity consumption and production for July. electricity can be injected into the electricity grid or dissipated, resulting in low \(SC\). In case of insufficient production of electricity from the PV system, energy is taken from the electricity grid, which leads to low \(SS\). Maximizing \(SC\) along with \(SS\) is the goal of the user. In Croatia, self-production is associated with renewable production and high-efficiency cogeneration for facilities with a capacity of \(<\)500 kW. The Renewable Energy Act obliges suppliers to purchase surplus electricity injected into the grid. In doing so, prosumers can have one of the following two statuses:  
_Self-supply plant user:_ a final customer of electricity of the household category who has a self-supply plant from renewable energy sources or high-efficiency cogeneration connected within his installations, whose surplus energy within the billing period can be taken over by a supplier or market participant with a contract, provided that within the calendar year, the amount of electricity that he delivered to the grid is less than or equal to the electricity taken from the grid.