Comment by sumea

If by Nordics you mean Norway, Sweden and Finland, then the most correct way to say would be that ground source heat pumps for redidential heating are (very) common in Sweden and Finland, especially in newer and larger buildings. Norway is somewhat different in energy and climate perspective than its eastern neighbours.

The biggest reason to not install ground source heat pump is high installation cost. This means that it makes more sense for larger residential buildings. Also If you have district heating available then this might be more economical in the long run.