Though it’s worth noting that that first 2 ton rated unit is putting out 0.5 tons (6k BTU/hr) at that temp and rating.
That’s not going to be particularly helpful for a structure that needed 24k BTU/hr during warmer temps, meaning the owner of the unit is likely mixing in a lot of 1.0 BTUs to meet the heat loss at -13°F.
> Though it’s worth noting that that first 2 ton rated unit is putting out 0.5 tons (6k BTU/hr) at that temp and rating.
I just did a quick search for "all" units and sorted the result list/table by COP@5F. If one was actually shopping/designing a solution then a more nuanced search criteria would be used.
Further, you'd probably want to do a (US ACCA) Manual J calculation to first determine how much energy is needed (j = joules)
* https://ashp.neep.org/#!/product/156605/7/25000/95/7500/0///...
An LG unit with 2.4 at -4F/-20C:
* https://ashp.neep.org/#!/product/29688/7/25000/95/7500/0///0
Searchable database of cold climate air source heat pumps (ccASHPs):
* https://ashp.neep.org/#!/product_list/