Enea Idled Units at Poland's Second-Biggest Power Plant Because a River Ran Low. It Is Building €1.53 Billion of New Gas Capacity on the Same Riverbank

On 6 August 2026, Enea idled generation units at two of Poland's largest coal-fired stations, Kozienice and Połaniec, because the Vistula had dropped too low to cool them. Tauron and Energa, running in the same heat, on the same grid, reported no interruption at all. Tauron's explanation was one sentence long: its plants use closed-loop cooling.

That sentence is the story. Two fleets, one weather event, opposite outcomes, and the difference is a capital decision taken decades ago that no lender, no rating agency and no capacity auction has ever scored.

One river, two cooling architectures

Kozienice is Poland's second-largest power station at roughly 4,016 MW of installed capacity, behind only Bełchatów. It and Połaniec draw cooling water straight from the river and return it warmer. This is once-through cooling, also called open-loop, and it is the cheapest way to reject heat ever built: no towers, no fan load, best-in-class heat rate. It works about 350 days a year.

Closed-loop plants recirculate water through cooling towers and give up efficiency every hour of their lives to do it. On an ordinary day that reads as a permanent tax. On 6 August, according to Polska Agencja Prasowa reporting carried by CEEnergyNews, it was the difference between selling into an emergency capacity window and watching one. Poland's transmission operator PSE declared exactly that window to hold the system together, and the energy ministry asked households and companies to cut consumption between 19:00 and 23:00 until 31 August.

The €1.53 billion sitting on the same bank

Here is the part that should make lenders sit up. In December 2025 Enea Elkogaz closed approximately PLN 6.45 billion (€1.53 billion) of project finance from a consortium led by Bank Gospodarstwa Krajowego, with PKO Bank Polski and Bank Pekao alongside and a KUKE guarantee. Enea called it the largest project finance deal in the history of conventional Polish power generation. The money builds two GE Vernova H-class combined-cycle units of 668 MWe each, 1,336 MWe in total, at Kozienice, with commissioning scheduled for 31 March and 30 June 2029.

Those units will sit on the riverbank that just failed. A combined-cycle unit rejects less heat per MWh than a coal unit, so the exposure is smaller. It is not zero, and it is not visible in anybody's base case.

Romania ran the same test on nuclear

Five days later, on 11 August, Romania's Ministry of Energy confirmed that Cernavodă was preparing Unit 2 for a controlled shutdown because Danube levels had fallen near the cooling pump suction area. The replacement plan tells you what cover costs: regional imports, the Rovinari 4 coal unit pulled out of reserve at the Oltenia Energy Complex, and Hidroelectrica topping up "within the limits of available water resources", which is a hydro producer being asked to cover a water shortage. Romania had already declared a 30-day state of alert on 6 August. Hungary's Paks plant hit the same Danube constraint in late July.

A European panel reviewed grid resilience on 12 August and found no short-term adequacy risk. That finding is correct and beside the point. The system held. The individual asset owners did not all get paid.

The cooling spread

Merchant thermal generation is underwritten on fuel spreads, carbon and capacity payments. Availability enters the model as a percentage, 92 or 94, with outages assumed random. Cooling-constrained outages are not random. They cluster on the hottest, lowest-flow, highest-price days of the year, which means they arrive exactly when the plant's option value peaks and when its correlation with the rest of the portfolio is at its worst.

Run that through a real price curve and the closed-loop efficiency penalty starts to look like an insurance premium rather than a design mistake. Tauron pays it every hour and collected on 6 August. Enea does not pay it and did not collect. Nobody publishes that spread, because nobody discloses cooling architecture as a financial variable.

What to fix before the next heatwave

The engineering answer is known and unpriced. Converting a once-through plant to hybrid or closed-loop cooling means towers, pumps, a permanent heat-rate penalty and a long outage. That is capex boards approve after a bad summer, which means the queue for tower suppliers, air-cooled condenser vendors and mechanical contractors starts forming now, across a thin European supply chain.

For sponsors the more urgent task is documentation. Every thermal asset inside a project finance structure should answer four questions on one page: what is the cooling architecture, which river or abstraction licence does it depend on, what flow or temperature threshold triggers derating, and how many hours has it lost to that threshold in each of the last ten summers. Most cannot answer the fourth. For system operators and regulators the same data settles a bigger question: whether a capacity market is buying megawatts, or buying megawatts that leave on the hottest evening of the year. Poland, Romania and Hungary paid for that answer in real time this month. The next round of thermal financing should charge for it up front.