Slovenia cuts Krsko output to 80%, pushing southeast Europe's nuclear curbs to 42% of capacity
Drought-driven reactor shutdowns across the Danube basin have nearly doubled Hungarian hub spot prices, leaving the region's supply margin thin.
Slovenia's 700 MW Krsko nuclear plant reduced reactor output to 80% from Thursday night (2026-07-30), operator Nek confirmed on Wednesday (2026-08-05), lifting curbs on southeast Europe's nuclear generating capacity to 42% from 40%.5 The reduction strips roughly 140 MW from a grid already stretched by a Danube drought that has forced widespread reactor shutdowns across the region.
The European Commission said on Tuesday (2026-08-04) it is closely monitoring risks to southeast Europe's power supplies and is ready to call an emergency meeting if conditions deteriorate further.4 That readiness signals regulators view the outage window as more than a routine summer derate.
The price response has been sharp. Spot power on the benchmark Hungarian hub nearly doubled to EUR 186.90/MWh on Monday (2026-08-03) compared with pre-disruption levels, according to Montel, as 40% of the region's nuclear capacity went offline before the Krsko reduction added to the total.4 Nuclear typically anchors baseload supply across southeast Europe, and with it curtailed, gas-fired generation sets the marginal clearing price.
European gas markets moved in sympathy. ICE Endex TTF front-month settled at EUR 55.74/MWh on Thursday (2026-08-06), up 6.78%, while German power gained 5.15% to EUR 131.16/MWh in the same session. [live prices] A sustained move in ICE Endex TTF front-month raises the switching level at which gas displaces coal in European generation, and with nuclear supply constrained across the southeast, the cost of keeping the system balanced rises further.
The Danube drought is squeezing the system from two directions. Low river levels constrain reactor cooling water intake, forcing deratings, but they also disrupt river-borne coal and fuel deliveries that several Balkan utilities rely on for thermal backup.4 The Commission's spokeswoman gave no threshold at which an emergency meeting would be triggered, leaving markets to price the uncertainty themselves.
One factor that would normally soften a supply shock is demand. European gas consumption has run about 10% below year-earlier levels, according to data cited in Economist reporting, which removes some pressure from the continental system.2 But the outage is geographically concentrated in a region with limited westward interconnection, and neighbouring grids cannot easily back-fill the missing nuclear megawatts even where spare gas capacity exists.
National price-cap policies complicate the demand response. France has capped gas prices at last year's level and electricity just 4% higher, while Italy, which generates 40% of its electricity from gas, has cut taxes on both fuels.2 Those measures blunt the conservation signal at the consumer level and sit uneasily alongside the EU's injunction that member states cut gas consumption by 15% across the board.2 As southeast Europe scrambles for replacement power, the gap between state-capped retail prices and the physical reality of wholesale markets widens.
Over a longer horizon, the region's utilities are working to reduce a different vulnerability. Finland's Fortum, Czechia's CEZ, Hungary's MVM Paks and Slovakia's Slovenske Elektrarne have signed an agreement with France's Framatome to develop a fully European fuel for VVER-type reactors, built on a 100% European design and supply chain including Framatome's assembly plants in France and Germany.1 The project addresses geopolitical supply risk. It does nothing for the megawatts missing from the grid now.
July's heat wave already forced a series of reactor deratings across France and the Balkans, and Montel reported the southeast European reductions are the sharpest yet this summer.3 If Danube flows stay low into late August, the 42% outage figure will rise further, and the Hungarian hub will continue setting the region's clearing price — at levels the market has not had to pay before from a drought-driven shortfall of this duration.4