IN Brief:
- Croatian wind and solar generation fell 54.3% in the week to 20 September while electricity demand declined 9.76%.
- Hydropower output increased 34.28%, but net electricity imports still rose 4.20%.
- Interconnection, hydro availability, and flexible generation remain central to covering abrupt changes in Croatia's domestic generation mix.
Croatia imported more electricity in the week to 20 September even as national demand fell, after a steep reduction in wind and solar output outweighed a substantial increase in hydropower generation.
Variable renewable generation fell 54.3% week on week, while hydropower output increased 34.28%. Net electricity imports nevertheless rose 4.20%, despite electricity demand declining 9.76% to 325.54GWh. Croatia’s average weekly electricity price moved by far less, edging down 0.35% over the period.
The figures show how quickly a national power balance can change when domestic generation moves faster than consumption. Lower demand reduced the amount of electricity that had to be supplied overall, but the decline in wind and solar production was substantially larger, leaving more of the remaining requirement to be met by hydro, thermal generation, and imports.
Croatian Transmission System Operator (HOPS) operates a transmission system connected with neighbouring countries and the synchronous network of continental Europe. HOPS also describes Croatia as a transit system within the SLO-HR-BIH control block alongside Slovenia and Bosnia and Herzegovina.
Those connections give Croatia access to neighbouring generation when its domestic production profile changes, although weekly import totals do not identify which resource supplied each individual hour. Physical flows and commercial schedules vary according to transmission availability, market prices, outages, generation costs, and conditions across neighbouring systems.
Hydropower provided a substantial offset during the week, but a 34.28% increase was not enough to reverse the movement towards higher imports. Hydro is inherently flexible compared with weather-dependent generation, yet operators cannot treat stored water as an unlimited reserve. Reservoir levels, inflows, environmental requirements, expected future prices, and plant availability all influence when water is converted into electricity.
The result was a supply mix in which imported electricity became more important even though consumption was falling. That combination is less unusual than it first appears: a system can require more imports during a period of weaker demand when domestic generation falls by a greater amount or when imported electricity is economically preferable to available local production.
Croatia’s small change in average weekly electricity price also illustrates the limits of using one price figure to describe system conditions. Hourly prices can vary widely within a week as renewable output, consumption, imports, and dispatchable generation move against one another. A relatively stable weekly average can therefore sit alongside a substantial change in the physical generation mix.
Renewable generation already plays a major role in the Croatian system. EU electricity data for the second quarter of 2026 showed Croatia recording one of the highest renewable shares of net electricity generation in the bloc, supported heavily by hydropower. The quarterly data are not directly comparable with a single September week, but they underline the influence that changes in hydro, wind, and solar availability can have on Croatia’s trading position.
The wider Southeast European network is designed to absorb differences between national generation portfolios, but the ability to do so depends on available cross-border capacity. A neighbouring market may have lower-cost generation available without being able to deliver it fully if transmission capacity is constrained, undergoing maintenance, or already committed to other flows.
ACER’s 2026 assessment of Southeast Europe identified both limited cross-border capacity and shortages of flexible resources as contributors to previous periods of regional price stress. The regulator called for better use of existing transmission infrastructure, faster network investment, stronger regional coordination, and greater participation from storage, demand response, and other flexible assets.
Croatia’s weekly figures are less dramatic than the price spikes examined by ACER, but the operating principle is similar. A large reduction in variable renewable output has to be absorbed somewhere in the system, whether through hydro, thermal plant, storage, demand flexibility, or imported electricity. The available mix changes hour by hour rather than according to a fixed hierarchy.
Autumn will alter that balance again. Solar production becomes more seasonal, wind conditions can strengthen or weaken sharply, hydro availability depends on rainfall and reservoir management, and electricity consumption will begin to move towards its winter profile. Croatia’s transmission connections give the system several options when domestic generation changes, but the week to 20 September showed how quickly those connections can become more important even while total demand is falling.
