France could face power cuts on Monday because of cold weather and delays to the restart of nuclear power after repair work, which will lead to demand outstripping supply, analysts said.
It has been expected that nuclear power supply would reach about 40 gigawatts this week, but operator EDF's delay in restarting reactors meant it rose to only about 35GW, leaving France more reliant on imports and gas-fired production.
As a cold spell grips north-western Europe this weekend and next week, Refinitiv analyst Nathalie Gerl said the situation could be "much more critical" but that there were plans to curb demand, especially for big industrial users.
There was still a risk of a shortfall on Monday, Ms Gerl said.
"If we remain at 35GW, next week, Monday could become quite tight," she said.
"We expect the demand at otherwise seasonally normal levels, but 35GW of nuclear would be too low to meet a possible demand peak at 73GW."
The EDF schedule shows 3GW of nuclear power returning to the grid next week, putting total capacity at 38 GW for the first cold spell of the peak demand winter season.
Grid operator RTE said on Thursday evening that there was no risk to security of supply on Monday, even with the cold weather and low nuclear availability.
RTE said earlier that France might face "some days" this winter when there was too little electricity supply.
What is driving energy markets - Business Extra podcast
What is driving energy markets - Business Extra
Vincent Balouet, chief executive of crisis management advisory Maitrise des Crises, told Reuters that operators, as a first step, could lower voltage on the grid by between 1 and 3 per cent, a difference households would barely notice.
Other measures, which the government has said are already in place to ensure enough power for critical factors such as hospitals and traffic lights, include asking major industrial demand centres to be ready to temporarily cut use in return for financial compensation.
