Power prices across Southeast Europe moved from scarcity levels close to €200/MWh in midweek to zero and negative values during Sunday’s solar peak, while evening prices still rose above €225/MWh. The shift highlighted constraints affecting flexibility and transmission capacity during the same weekly cycle.
SEEPEX day-ahead baseload swings in Serbia
Serbia’s SEEPEX market recorded a reversal over the week, rising to €184.92/MWh on Sept. 3 before falling to €60.19/MWh on Sept. 6. The change coincided with firmer renewable output and lower weekend demand replacing nuclear-driven scarcity during daytime hours.
The same week also showed that Hungary and Romania did not follow Serbia’s pattern at the same pace. Prices in those markets were near €197/MWh at the midweek peak, with evening hours above €275/MWh, indicating continued tightness after sunset.
Aug. 31 to Sept. 6: regional tightening then oversupply
The period from Aug. 31 to Sept. 6 illustrated a change in Central and Southeast European power-market structure. Firm-generation constraints, nuclear outages and higher weekday demand tightened prices through the first half of the week.
As renewable output increased and weekend consumption fell, prices dropped sharply across the region. SEEPEX day-ahead baseload increased from €132.21/MWh on Aug. 31 to €166.25/MWh on Sept. 1, €173/MWh on Sept. 2 and €184.92/MWh on Sept. 3.
Prices then declined to €149.76/MWh on Sept. 4, €114.47/MWh on Sept. 5 and €60.19/MWh on Sunday, representing a roughly two-thirds fall from Thursday’s peak.
Nuclear loss and imports raise evening pressure
Hungary and Romania were considerably tighter during the middle of the week, with delivery for Sept. 3 clearing at around €196.57/MWh in Hungary and €196.82/MWh in Romania. Bulgaria, Greece, Croatia and Slovenia were clustered mostly between €190/MWh and €193/MWh for that delivery.
Romania’s continued loss of nuclear generation was cited as a factor behind the tighter conditions. With Cernavodă unavailable, the system relied more heavily on imports, fossil-fuel generation, hydro and renewables, increasing pressure on neighbouring Hungary and Bulgaria.
The impact was particularly visible during evening hours, when Hungarian power reached about €276.5/MWh during the Sept. 1 evening peak and Romania climbed to around €283/MWh.
Geographical fragmentation: Germany cheaper as flows rise
A second feature of the week was widening geographical fragmentation between markets. Germany became significantly cheaper than Central SEE markets even as west-to-east electricity flows increased.
For Sept. 3 delivery, German day-ahead baseload fell to around €133.62/MWh, leaving Hungary almost €63/MWh higher at roughly €196.57/MWh. The divergence widened further on the next day when Germany dropped to about €88.95/MWh, while Hungary remained at about €179.78/MWh, creating a spread of almost €91/MWh.
The persistence of that premium was linked to transmission congestion rather than an overall shortage of electricity.
Sunday solar peak: negative prices alongside high evenings
Toward the end of the week, rising solar production and lower weekend demand reversed pricing patterns again. Hungary, Romania, Slovenia and Croatia recorded negative prices during Sunday’s solar period, while Bulgaria and Greece traded around zero for several consecutive daylight hours.
In Hungary, electricity fell to around -€1.5/MWh near 13:00 before rising to roughly €227.7/MWh at 20:00. Romania followed a similar pattern, falling to around -€1/MWh, then climbing back toward about €228/MWh in the evening.
The pattern indicated that solar-driven oversupply was becoming increasingly regional rather than confined to a single market.
Divergent timing affects cross-border balancing after sunset
The ability of interconnectors to absorb surplus depends on whether neighbouring systems are also long at similar times; effectiveness falls when multiple countries experience strong renewable output simultaneously. After sunset, synchronisation reverses as countries compete for hydro, gas, nuclear output, storage and imports.
This timing shift affects how value is captured across assets with different flexibility characteristics compared with standalone solar output concentrated in low-price hours.
CW36 volatility keeps Serbia-Hungary spread unstable
The week also showed Serbia trading differently from the Central SEE core despite brief convergence toward Hungary during midweek tightening. As renewable availability increased again, the discount widened once more.
SSEEPEX fell from €184.92/MWh on Thursday to €60.19/MWh on Sunday while Hungary remained structurally firmer at higher levels through the period described for evening tightness.
The volatility indicated that the Serbia-Hungary spread can shift quickly with changes in domestic generation, imports, cross-border schedules and network constraints within a single weekly cycle.
A market showing both daytime surplus and post-sunset scarcity
Southeast Europe ended the week with both surplus conditions during daylight hours and scarcity conditions after sunset within the same market cycle described for CW36. Abundant renewable electricity coincided with insufficient flexibility and transmission capacity to move supply where it carried more value later in the day.