I have a new home heated with a heat pump. I have been told that heat pumps do not heat very well at low temps. Mine has been doing real well until last night when the temperature got down to 4 degrees F. The heater maintained the temperature at 68 but seldom shut off all night long. It is a 5 ton unit heating a custom built home of 2200 sf. The insulation is excellent in ceiling and walls. All windows are Anderson insulated windows. Very good windows.

Is this normal for the pump to run this way? Is there something I am failing to do for the heater to be more efficient.

Thanks

As the outdoor to indoor delta gets greater (aka lift increase) your BTU output from the HP will drop. So, yes, it will have to run longer to produce the same BTUs per hour.

At 4F OD temp I would expect some kind of aux/backup (furnace, heat strips) to be assisting.