Danube drought strips Hungary of 1,760 MW

The Danube dropped so low last week that Hungary lost nearly all its nuclear power, Romania is days from losing its last working reactor, and governments across the region are telling factories to stop so that households can keep the lights on.

How a river switches off a reactor

Nuclear plants use river water to carry away waste heat, the cold side of the system that converts nuclear energy into electricity. When the river drops, pumps can't draw enough water. When it runs warm or slow, discharged water pushes downstream temperatures past legal limits. During a drought, both problems hit at once.

At Paks, Hungary's only nuclear station and normally a 2,000 MW source, the shutdown came in stages. State energy company MVM began cutting output when the Danube fell past -106 cm at the plant gauge (MVM Paks). By 2 August, only one of eight turbogenerators was still running at roughly 240 MW (Portfolio, Telex). AP reported a full shutdown (AP). Either way, Hungary lost the vast majority of its nuclear baseload (the steady output that runs around the clock) in days.

Romania's situation is tighter. At Cernavoda, Unit 1 was already offline. Unit 2 stayed connected, but the supply basin sat at 2.02 metres, just 12 centimetres above the level where pumps stop (Ziua de Constanta). A side channel near the Bala canal was pulling roughly 85% of Danube flow away from the plant's cooling intake. The military used controlled explosions to redirect water back toward the plant (Radio Constanta), buying an estimated four to five more days (Agerpres).

Solar covers midday, not the evening

Romania's daytime numbers look manageable. On 3 August the country generated 6,009 MW against 5,212 MW of demand, with solar covering more than 45% (Agerpres). After sunset, solar vanishes while air conditioning keeps running. By the evening of 31 July, Romania was producing 5,239 MW, consuming 7,177 MW, and importing 1,938 MW to fill the gap (Radio Timisoara). That evening shortfall is where lost nuclear power actually bites.

Europe links national power markets through interconnectors, the high-voltage cables that move electricity from cheaper to pricier zones. When Hungary and Romania both needed replacement power at the same evening hours, the cables became the scarce resource. Slovenia's grid operator ELES limited cross-border capacity on the Austrian border for 3 August (ELES). Wholesale prices surged past €150/MWh, with evening peaks near €270/MWh, far above typical summer rates (Serbia Energy).

Factories absorb the hit so households don't

Both governments chose the same order: industry first. Hungary's emergency decree empowered grid operator MAVIR to cut or disconnect large industrial and commercial users, with households protected until last (HVG). Prime Minister Péter Magyar said large consumers had committed more than 630 MW of voluntary reductions by 3 August (Telex). That helps, but Paks normally provides 2,000 MW; voluntary cuts alone cannot close the gap.

In Romania, carmakers Dacia and Ford voluntarily halted production until 19 August, freeing about 200 MW (Agerpres). Nuclearelectrica, which runs Cernavoda, warned customers it may not be able to fulfil delivery contracts (ZF).

Household bills are shielded for now by fixed contracts. That protection is real, but it works only because factories, cross-border imports and the grid are absorbing the shock. Every megawatt of curtailed production means delayed cars, disrupted supply chains and losses that show up later. The system held through the weekend. If rivers stay low, the question is whether voluntary savings become mandatory rationing, and whether replacement power at €270/MWh stays affordable enough for governments to keep shielding households at industry's expense.