[sokoloff]

Even at 17°F OAT, a modern heat pump can be over 2.5 CoP and deliver 90% of its rated capacity. [1]

Even on a day with the low in the teens, the high was probably 10-15° higher. Look at the hourly bin data for your location, not just the daily/monthly lows.

The key with a heat pump in a heating dominated climate (on top of insulation which is needed for any energy source) is sizing it right, creating the ducts right, setting the control strategy to not use H2 (emergency heat) too liberally, and not using deep setbacks that will flip you into H2.

Just as you are rightly skeptical of people who can’t comprehend not installing AC, you might be skeptical of drawing too strong and long conclusions from one heat pump install in a rental of unknown quality and where the incentives aren’t aligned to trade-off capital vs operating costs.

[1] https://www.pacificairconditioner.com/files/Hyper_Heat_for_r...