Mitsubishis can work down to -13F/-25C and have a COP of 2.08: * https://mylinkdrive.com/viewPdf?srcUrl=http://enter.mehvac.com.s3.amazonaws.com/DAMRoot/Origin

Mitsubishis can work down to -13F/-25C and have a COP of 2.08: * https://mylinkdrive.com/viewPdf?srcUrl=http://enter.mehvac.com.s3.amazonaws.com/DAMRoot/Original/10006%5CM_SUBMITTAL_MSZ-FS12NA_MUZ-FS12NA_en.pdf https://mylinkdrive.com/viewPdf?srcUrl=http://enter.mehvac.c... If you live in US IECC Climate Zone 4 or above look for a cold climate air-source heat pump (ccASHP): * https://neep.org/heating-electrification/ccashp-specification-product-list https://neep.org/heating-electrification/ccashp-specificatio... * https://ashp.neep.org/#!/ https://ashp.neep.org/#!/ You can also get things installed in a dual fuel arrangement where you still have a gas furnace that kicks in if it does ever get 'too cold'.