

Air conditioners are heat pumps.
Air-to-Air heatpumps (i.e. AC) are trivial to install in apartments (drill one inch hole in wall, mount compressor on one side and head unit on other, done,) and make for very efficient heating in winter just as much as they can be used for cooling in summer.





Don’t include Romania in this - we already have AC. The weather currently getting everyone in north-west Europe highly exercised is a mild summer day in Romania. I assume this is also true of Bulgaria.