Have a heat pump that was grafted into our central air in Montana. We absolutely adore it. It doesn't work every day of the year - winters can get bitterly cold

Have a heat pump that was grafted into our central air in Montana. We absolutely adore it. It doesn't work every day of the year - winters can get bitterly cold. But it works for somewhere around 320 days out of the year. We kept our gas heater as backup, and it rarely kicks in.