Croatian power traded below zero for 257 hours last year, and the regulator reads it as a case for batteries
HERA's annual report: negative-price hours on CROPEX rose from 196 in 2024 to 257 in 2025, mostly in spring and on sunny Sundays. HERA calls it an important signal for battery storage and notes strong investor interest in connecting storage.
On a sunny spring Sunday, a Croatian factory that is shut for the weekend has panels pushing power into a grid that does not want it. In those hours, the exchange price can drop below zero.
Balkan Green Energy News reported on 23 July 2026 from the annual report of HERA, the energy regulator. Hours with negative prices on CROPEX, the Croatian power exchange, rose from 196 in 2024 to 257 in 2025, about 30% more. They cluster in spring and on sunny Sundays, when solar output is high and demand is low.
HERA gives the causes: surplus output from seasonal sources, and older incentive schemes that take everything fed into the grid. Parts of the current framework already suspend the market premium for new contracts when prices go negative. HERA calls the trend an important signal for building storage, especially batteries, and notes strong investor interest in 2025 and 2026 in connecting storage to the transmission and distribution grids.
Power Trading News Europe added the scale on 27 July: 257 hours is about 2.9% of the year, close to 10.7 full days. It also points out that the bigger revenue hit for solar comes from the many hours priced low but still above zero.
Analogy: it is a farmers' market at closing time on a hot day. Everyone has too many tomatoes at once, and some stallholders pay you to take a crate. By evening, nobody has any left to sell.
Good: an official regulator count, year on year, with an official reason. A buyer weighing a battery beside a roof array can cite HERA, not a vendor slide.
Bad: these are exchange hours, not your retail bill. Most businesses buy on a supplier contract, so a negative hour on CROPEX does not automatically turn into a credit on the invoice.
Ugly: 257 hours is under 3% of the year. A battery case built only on negative hours is thin. The cheap-but-positive midday hours and the expensive evening ones matter more, and they are not in this count.
Source: Balkan Green Energy News, 23 Jul 2026 - number of hours with negative electricity prices rises 30% in Croatia; Power Trading News Europe, 27 Jul 2026 - Croatia's 257 negative-price hours.