Gen 1 doesn't have a heat pump. AC only. Heat pumps have to work pretty hard when there is a significant temperature delta.I had my Gen 1 R1T early ass VIN LE in for some service and was given a brand new Gen 2 TriMax loaner (thank you very much Rivian!). I even pealed the plastic off the screen. Anyhow, the heat pump on it was so insanely loud I couldn't believe it. My gen 1 is whisper quiet in comparison. Maybe this one was a buy back, but if all of them sound that way, I'm not upgrading for some time. That was the first Gen 2 I have driven, just fyi... The dynamic glass was pretty cool though.
I'm not an expert, but I'm still assuming the monthly electricity cost is significantly higher relative to gas in those temp ranges.There are home heat pumps that are effective even below 0 degrees F - Cooper and Hunter sell such units.
That assumes you have natural gas. Quite a few areas have very expensive heating oil so a cold weather heat pump saves a lot of money.Seems to me like these automotive heat pumps, similar to those for home heating, are effective and efficient down to maybe 40degF and beyond that are overworked, loud, and maybe not completely effective on their own in single digit or lower temps. If your State borders Canada, you probably don't want a sole electric heat pump for all your heating in your home because the electricity cost would be double your gas bill. And you probably want a Gen 1 R1.