It got down to eighteen degrees Fahrenheit last night. When I got home this morning, it was still in the low twenties.
I have the temperature in my bedroom set at 68, and the rest of the house at 66. All the units were in operation upon my arrival. My bedroom felt like it normally feels.
My biggest concern was the single 12K BTU unit on the living room wall that is responsible for heating the living room, kitchen, and the first part of the hallway. Roughly half of this space has no ceiling, just an insulation barrier, which has small gaps here and there. Also the floor repair is not complete, meaning that there are areas where cracks as wide as a quarter of an inch are open to the crawl space, with no insulation to stem the flow of cold air.
Even so, the temperature in the kitchen, which is around the corner from the unit was 61. Not terrible for a heat pump with no emergency heat option or furnace for backup. I don’t know how long it will last, but performance is acceptable. After the house is finished and the crawl space insulated, I predict that any reasonable temperature setpoint in this climate will be within its capabilities.