Germany rejected on Wednesday moves to retain one nuclear power station as a backup to avert blackouts during the risky decade ahead when the country abandons all nuclear energy.
The Federal Networks Agency, which was commissioned in June to draw up a supply plan, confirmed the immediate closure of eight out of Germany's 17 nuclear electricity plants as decided by the German parliament.
There had been calls to put one of the eight closed stations on standby this winter as power use peaks, with its fuel loaded and staff on duty, because the only other alternative was to use elderly, polluting and more expensive fossil fuel-burning plants.
Economists have warned that Germany is cutting it close with the nuclear plant closures, since it will take years to build enough wind turbines and gas-fired and coal-fired plants to replace them.
"We won't have to reactivate a nuclear power plant," said Matthias Kurth, president of the Networks Agency, while adding that power supply in Germany would be "very tight" for several years.
His agency has designated a series of gas and coal plants in Germany and Austria to provide 2,084 megawatts of reserve power this winter.
Kurth said German consumers and industry must expect to pay higher power charges from keeping those sites in a standby state.
"But we have to be willing to pay for security," he said.
Germany aims to close all its nuclear plants by 2022. Surveys since the Fukushima nuclear disaster in March in Japan show most Germans want to be rid of nuclear power as soon as possible.