For modern heat pumps (e.g. Daikin Altherma) the COP at -2c will be around 2.8-3. They operate down to -25c in heat pump mode, then automatically switch over to

For modern heat pumps (e.g. Daikin Altherma) the COP at -2c will be around 2.8-3. They operate down to -25c in heat pump mode, then automatically switch over to resistive heating. I live in Lithuania (-20c and lower during winter is not uncommon) and almost all new houses have them. You can no longer use gas for heating in new builds. 3kW of solar generates more than enough power (with net metering) to run a heat pump over the course of a year for the average size house (150m2)