well my 80m2 apartment is fully heated to about 22.5C with an air heat pump drawing about 600W with an outside temperature of 0C. So take from that what you will about efficiency.
That's no particular feat, you can heat a forge to 1200C with enough insulation and just 600W. Also, this is just considering a limited referential, ie. the one impacting the most your wallet. If you consider a bigger referential, your efficiency will drop below 1 for sure. Not to mention that your system will leak refrigerant (it's really not a matter of "if" but "when"), which is likely to have greenhouse effects.