I do have a mini-split AC which can also provide heat. It is OK for autumn and spring but it is a no match for a radiator heating when it's really cold outside

I do have a mini-split AC which can also provide heat. It is OK for autumn and spring but it is a no match for a radiator heating when it's really cold outside in the winter. Yes, of course I can run the lines through the whole apartment but this is a much costlier proposition.