Germany is to temporarily halt the phasing-out of two nuclear power plants in an effort to shore up energy security after Russia cut supplies of gas to Europe’s largest economy. The economy minister, Robert Habeck, announced on Monday that the power plants, Neckarwestheim in Baden Württemberg and Isar 2 in Bavaria, are to be kept running longer than planned in order to be used as an emergency reserve until the middle of next year. Habeck said that after a stress test carried out with four grid operators, considered worst-case scenarios, they had come to the conclusion that “hourly crisis-like situations in the electricity supply system during winter 22/23, while very unlikely, cannot be fully ruled out”. He insisted that Germany had “very high supply security” and that the two nuclear plants should remain “on standby until mid-April 2023, in order, if necessary, to provide an additional contribution to the electricity grid in southern Germany”. The nuclear power plants would be available for operation, and fully staffed, but only on standby and would not produce electricity unless it was deemed necessary. He insisted that Germany would continue to stick by its plans – regulated by law – to withdraw from nuclear power. The plants were due to be mothballed by the end of December, the last of Germany’s nuclear power plants to cease working, after a dramatic 2011 decision by Angela Merkel, the then chancellor, in reaction to the Fukushima nuclear accident in Japan. The extraordinary upending of energy markets since Russia’s invasion of Ukraine in February has however led to a dramatic rethink. Power bills across the continent have been soaring in light of dwindling supplies, putting households and businesses under extreme pressure as winter approaches. The sense of urgency increased when Russia failed to turn on the fifth and last functioning turbine on the Nord Stream 1 pipeline which had carried gas from Russia via the Baltic Sea to Germany. Moscow cited faults on the line, which it said were linked to the sanctions imposed on it. Discussions on extending the lifetime of the plants have triggered a heated debate in Germany, where nuclear power has been a source of controversy for decades. An announcement by Habeck, a leading figure in the anti-nuclear Green party, on restarting the plants would once have been unthinkable, but the party has come under increasing pressure, especially from its coalition partner, the pro-business FDP, to pause the phase-out. Many in the FDP hope that today’s announcement may lead to a complete rethink on the phase-out policy, arguing that nuclear power would help Germany achieve its zero-carbon emission goals sooner, as well as helping to secure long-term energy security. The Green party has rejected this position. “In the winter, our towns and cities will in part be darker because of the fact we have to save electricity. In this situation we should not forgo safer and climate-friendly ways of producing electricity such as nuclear power. This requires more than just extending their operation,” said finance minister Christian Lindner, who is head of the FDP. Already Germany had been forced to restart mothballed coal-fired power plants, considered the most environmentally damaging source of fuel, which Habeck has stressed was a temporary and painful but necessary measure. So far polls show that the majority of Germans are understanding of the need to at least temporarily revert to nuclear power, given the urgency of the situation, even if they don’t like it. Habeck has also been trying to fill Germany’s gas storage facilities, using supplies from Belgium, Norway and the Netherlands. Despite Russia’s total switch-off, storage levels stood at just under 86% on Monday. Dmitry Peskov, the Kremlin spokesperson, said on Monday that the failure to resume supplies from Nord Stream 1 after the impromptu maintenance work was owing to “problems with pumping gas [that] arose due to sanctions that were imposed against our country”. Extending the lifetime of the plants is, though, not expected to boost Germany’s energy supplies by much. Habeck has said they make up just 2% of Germany’s electricity output. He had repeatedly ruled out resurrecting the plants, while chancellor Olaf Scholz had said it “could make sense”. Scholz unveiled a new series of inflation relief measures on Sunday, amounting to 65bn euros and encompassing everything from a rise in child support to assistance in housing benefit to cover high energy bills. Groups and political parties of the far left and far right have pledged an autumn of protests against higher living costs, the first of which is due to kick off in the eastern city of Leipzig on Monday evening.