Europe has spent decades shutting down coal-fired plants to combat global warming. Now the ones still left are experiencing an unexpected windfall.

Soaring natural gas prices have transformed the economics of coal plants just as cold weather pushes up demand and fading solar output leaves Europe needing more conventional generation. In Germany, one measure of profitability for generating electricity from lignite has surged to €64 per megawatt-hour this month from virtually zero a year ago, according to Energy Aspects Ltd.

“Coal-fired power plants are benefiting significantly from tight European power markets, with all available capacity running,” said Michael Schrettle, an analyst at industry consultant Volue AS.

The development exposes an uncomfortable reality for Europe’s lawmakers and the energy transition. As countries shut coal plants, those that remain become more valuable whenever conventional generation is needed to back up intermittent wind and solar, giving operators less of an incentive to close them.

Europe’s remaining plants are mainly located in Germany and Poland, which accounted for more than 74% of the European Union’s power output from the fuel last year, according to Ember. Germany has about a dozen large coal-fired units operating in the commercial electricity market. Some other plants have been withdrawn from the market, but kept in the nation’s grid reserve.

The remaining capacity is owned by a small number of operators, with RWE AG and Lausitz Energie Kraftwerke AG together accounting for the majority of large-scale coal capacity. In Poland, Polska Grupa Energetyczna S.A. is the largest owner.

Germany is particularly exposed as it shut its last nuclear reactors and plans to phase out coal while relying increasingly on renewable power. But new gas plants intended to provide backup are yet to be built, leaving the country’s existing coal fleet crucial when renewable generation is low.

Profits could increase further as winter sets in. The clean dark spread for lignite is expected to rise even further to €70.50 per megawatt-hour from next month through March, according to Energy Aspects.

Hard-coal plants are also back in the money, with the spread averaging €37.30 per megawatt-hour in October compared with a negative €11.60 a year earlier.

“The spreads are expected to stay high through March,” said Sabrina Kernbichler, analyst at Energy Aspects.

One potential drag for hard-coal plants is the cost of getting fuel to them. Water levels on key rivers such as the Rhine have remained low for months, pushing up transport costs, and some operators have warned they may have to curb output as a result.

Most coal generators sell much of their power ahead of the winter, limiting their exposure to current prices. But any remaining unhedged volumes could result in a higher profit because of the currently elevated clean dark spreads, said Peter Crampton, an analyst at Barclays Plc.

For now, those margins, are giving operators every incentive to maximize output. German coal-fired power generation in October is averaging 14% higher than in the same month a year earlier, while gas generation is down by around 20%, according to Entso-E data. A similar development can be seen in Poland, according to data from the Fraunhofer Institute.

“Since coal produces roughly twice the carbon dioxide per megawatt-hour of an efficient gas plant, that could increase power-sector emissions this autumn and winter,” said Patricio Alvarez, an analyst at Bloomberg Intelligence.