France remained Europe’s biggest net exporter of power as the continent’s energy crunch unfolded, even as its nuclear reactors curbed output and domestic heating demand surged at the end of 2021.

While France’s exports to its neighbors remained high during the third quarter, the picture was more variable in the fourth, analyst EnAppSys said in a report. The country became a major importer as electrical heating demand pushed up prices over November and December, incentivizing inward flows.

“This cold December for France came alongside high demand, low wind and hydro generation, followed by a series of nuclear maintenance outages toward the end of the year,” Jean-Paul Harreman, EnAppSys director, said in an emailed statement. Those outages “contributed to the lowest nuclear availability levels in recent history.”

Since December, EDF has cut the forecast for French nuclear output twice, which may further limit exports in the coming years. It will also increase exposure to a high gas and coal price for neighboring countries dependent on fossil fuels.

Despite the winter reverse, France still exported 21.5 terrawatt-hours of power in the second half, with Sweden and Norway the next biggest exporters. For French power, Italy and Britain were the major destinations; those countries were also the largest net importers of power overall during the second half.

The U.K. increased its imports capacity with a new cable to Norway, but still drew substantial imports from France, the Netherlands, and Belgium, with capacity constraints limiting Norwegian flows.

Overall exports from the Nordic region were also hampered by some of the coldest seasonal temperatures in 50 years during November and December, which boosted domestic demand, according to the report.