France may face "some days" this winter when insufficient electricity supply could mean power cuts, the head of French energy regulator RTE said, as the government briefed local authorities on how to manage any possible outages.
"The situation entails risks, but one must not think power cuts are inevitable," Xavier Piechaczyk told France Info radio.
Mr Piechaczyk stuck with the watchdog's last supply forecast, which had highlighted risks of shortages in January.
"Today we have 35 gigawatt of available nuclear power as of December 1, the aim is to reach between 40 and 41 on January 1 and to end the month at around 43, compared to a total capacity of 61."
Mr Piechaczyk said the forecast was modelled on EDF's nuclear maintenance schedule, with some additional delays already anticipated.
EDF has faced an unprecedented number of outages at its fleet of nuclear reactors, reducing nuclear output to a 30-year low just as Europe scrambles to replace Russian gas supplies, which Moscow cut off in retaliation for European Union sanctions imposed over its invasion of Ukraine.
In RTE's scenario, there is a risk of "some days this winter" when the country's electricity monitoring application Ecowatt will display a red signal, Mr Piechaczyk said. This would trigger a need to load users partially off the power grid.
Ecowatt is an app designed to allow consumers and businesses to monitor the power situation in real time so they can reduce consumption and avoid power cuts if the watchdog gives a warning signal.
Mr Piechaczyk acknowledged that so far not enough people use the app. "We have 470,000 thousand subscribers to the SMS alerts and our app was downloaded around 300,000 times. That's not enough, we have to do more advertising," he said.
Analysts told Reuters that cold weather could lead to initial power shortages as early as Monday.
"If we remain at 35 GW, Monday next week could become quite tight - we expect demand at otherwise seasonally normal levels, but 35 GW of nuclear would be too low to meet a possible demand peak at 73 GW," Refinitiv analyst Nathalie Gerl said.
However, Frederic Lefort, head of business and administrative clients at Engie, one of the main power suppliers, told an event on Thursday that "we don't expect any red alert until the end of 2022".
The French government has sent binding instructions to regional government officials, seen by Reuters, which provide details on how to prioritise power allocation. It also urges them to meet with local authorities and businesses to make sure all emergency power generators are working.
