The EU has the following target in place for the sharing of electricity:

The EU has set an interconnection target of at least 15% by 2030 to encourage EU countries to interconnect their installed electricity production capacity. This means that each country should have in place electricity cables that allow at least 15% of the electricity produced on its territory to be transported across its borders to neighbouring countries.

The main reasons to do this is that it is good for renewables and it is good for overall resilience. The UK, for example, has one of the largest offshore wind markets in the world. But if it's having a bad wind year, interconnections allow it to import the electricity it may need -- perhaps from Norway, which is Europe's biggest producer of hydropower.

Here is what that looked like in 2021 (via the FT):

Of course, this works really well when there's enough electricity to go around and everyone is cooperating. The question this winter is whether that changes at all.