I have bougth 2 heat pumps this year and will propably buy the 3rd later this year. As some of you know I live in finland where its really cold in winter. I still did not want to spent big bucks to nordic climate heat pumps. I bougth best I could afford ones Panasonic KIT CS-FZ35WKE. It worked well on temps when it was maximum of -10 celsius but it started to freeze the outer unit slowly but steadily. I knew that it will happen and I have to install a heating cable to the outer unit, Which I did a 35w 2 meter long cable.
That boosted little bit the performance and it now worked well to around -15 celsius, but if it get colder than that inside temps started to drop. Well my house is pretty big which is one reason. I measured outer unit temperatures and noticed that the stock insulation in the pipes and connectors were not good. I added more insulation materials on the outer unit walls in made double insulation to coolant pipes.
After those mods the impact to heating was big. Not inner unit max temps get +10 celsius hotter and its able to keep inside temps on +20 celsius to aroung -20 celsius. Pump did not newer shut down even at -35celsius but it did not make any heat either at those temps so more work is ahead.