That's a COP of 2.8. You have to check the efficiency graph and your mean winter temperatures, because I suspect it operates fully resistive at below -10°C or s

That's a COP of 2.8. You have to check the efficiency graph and your mean winter temperatures, because I suspect it operates fully resistive at below -10°C or so. I also noted underwhelming performance and increased faulty compressor incidence for air source heat pumps with the external unit mounted on Northern walls (in the Northern hemisphere). I suspect it doesn't get sunshine and the defreezing resistive element is operating a lot, driving up energy costs.