Some Mississippians believe that heat pumps can't work properly with the often radical weather conditions in the state, but Graham said those rumors simply aren't true. The system works properly in areas where the average winter temperature is 25 degrees or above. In Mississippi, our average temperature in the winter is well above that number. Heat pumps are rated for heating and cooling in terms of capacity and efficiency. Heating efficiency for air source heat pumps is indicated by the Heating Season Performance Factor.
Heat pump efficiency depends on outdoor temperature.
The performance of an air source heat pump in heating and cooling mode decreases with the drop in outside temperature. The HSPF is therefore higher in mild climates than in cold climates. It's the consumer's choice whether or not to cool the home during the summer, but there is no choice when it comes to heating the home in the winter. It simply has to be done. Heat pumps can accomplish this more economically and efficiently than most alternatives.