I'm not an expert on the topic, but I imagine that a heat pump that can handle -20F is also much more energy efficient when the temp is 0F (in comparison to a h

I'm not an expert on the topic, but I imagine that a heat pump that can handle -20F is also much more energy efficient when the temp is 0F (in comparison to a heat pump that was rated only for -5F, operating at 0F).