## 3 Results and Discussion
### Load and Electricity Generation in July 2024  
Figure 4 shows the observed (historical) net power load and the net electricity generation by energy source in July 2024. The electricity demand is represented by the black curve, which shows significant daily fluctuations, with a smaller morning peak, lower demand during working hours, bigger peak in the evening hours, and lower demand at night. Throughout the week, demand is higher during weekdays (Monday-Friday) but lower during weekends (Saturday-Sunday). In July 2024, the weekend days were 6-7, 13-14, 20-21, and 27-28 July. Croatia experienced the heatwave over a two-week period, from 8-21 July, when the power load increased considerably due to higher electricity consumption for air conditioning and cooling. The maximum peak load and the overall historical record occurred at 19:30 on 17 July 2024, and was equal to 3381 MW.  
From Figure 4, it can be seen that nuclear energy (red band) provides a stable and constant output, acting as baseload energy source. Croatia uses half of the electricity from the jointly owned nuclear power plant at Krsko, wh  
Figure 4: Observed load and net electricity generation by sources in July 2024, Croatia.  
696 MW. The coal-fired power plant (dark gray band) provides additional base generation and started operating on July 7 after a prolonged overhaul. Hydro run-of-river (dark-blue band) contributes additional baseload but is influenced by water availability. Hydro reservoir (blue band) and combined cycle gas turbine (CCGT) power plants (orange band) offer higher levels of flexibility and are used as baseload and peak generation units.  
In the summer months, water availability is reduced, and hydro reservoir units are mostly used to mitigate the peak load in the evening hours, after production from solar PV ceases. The category of hydro reservoir includes production from the largest pumped hydro storage power plant in Croatia (RHE Velebit, +276 MW/\(-\)240 MW). Onshore wind (light-blue band) shows an intermittent contribution, dependent on wind availability. During the heatwave of July 8-21, production from onshore wind is reduced relative to the first and last weeks of July 2024. Biomass and other renewables (green and olive bands) contribute with a smaller but steady production profile, approximately 115 MW in total, improving the energy mix diversity. The solar PV category (yellow band) is expected to grow fast in the next years, thanks to simplified permitting procedures and faster grid connections. The gap between power load and electricity generation indicates the import-export electricity balance. At 19:30 h on July 17, a maximum instantaneous electricity import share of 35% was recorded (1185 MW out of 3381 MW). Croatia imported electricity from Slovenia and Hungary, which acted primarily as transit countries, while the necessary electricity was mostly generated in countries with large solar PV capacities further north (e.g., Austria and Germany). Renewable energy sources supplied 39.2% (1324 MW) of the demand. The remaining 872 MW (25.8%) was produced in non-renewable energy sources.  
Figure 5 shows the observed hourly load profile and net electricity generation for the average day in July 2024. Domestic net electricity generation was consistently lower than the power load and the necessary demand was met by import electricity. The peak load of the average day in July 2024 occurred in the evening hours, between 19:00 and 21:00 h, with values close to 2900 MW. Net electricity generation from domestic power plants was between 1500 and 2000 MW. However, up to 1000 MW of the power load had to be imported, most of it during daytime and evening hours.  
Figure 5: Observed hourly load and generation for the average July 2024 day in Croatia.